Mezacar

White to off white, biconvex, circular tablet having lip shaped breakline on one side and 'K' symbol debossed on other side.
Each uncoated tablet contains: Carbamazepine BP 200 mg.
Excipients/Inactive Ingredients: Microcrystalline cellulose, croscarmellose sodium, hypromellose, colloidal anhydrous silica, magnesium stearate, purified water.

Pharmacotherapeutic group: Anti-epileptic, neurotropic and psychotropic agent; Dibenzazepine derivative. ATC Code: N03AF01.
Pharmacology: Pharmacodynamics: As an antiepileptic agent its spectrum of activity embraces: partial seizures (simple and complex) with and without secondary generalisation; generalised tonic-clonic seizures, as well as combinations of these types of seizures.
The mechanism of action of carbamazepine, has only been partially elucidated. Carbamazepine stabilises hyperexcited nerve membranes, inhibits repetitive neuronal discharges, and reduces synaptic propagation of excitatory impulses. It is conceivable that prevention of repetitive firing of sodium-dependent action potentials in depolarised neurons via use- and voltage-dependent blockade of sodium channels may be its main mechanism of action.
Whereas reduction of glutamate release and stabilisation of neuronal membranes may account for the antiepileptic effects, the depressant effect on dopamine and noradrenaline turnover could be responsible for the antimanic properties of carbamazepine.
Pharmacokinetics: Absorption: Carbamazepine is absorbed almost completely but relatively slowly from the tablets. The conventional tablets yield mean peak plasma concentrations of the unchanged substance within 12 hours (chewable tablets 6 hours; syrup 2 hours) following single oral doses. With respect to the amount of active substance absorbed, there is no clinically relevant difference between the oral dosage forms. Carbamazepine is absorbed almost completely but relatively slowly from the tablets. The conventional tablets yield mean peak plasma concentrations of the unchanged substance within 12 hours (chewable tablets 6 hours; syrup 2 hours) following single oral doses. With respect to the amount of active substance absorbed, there is no clinically relevant difference between the oral dosage forms. After a single oral dose of 400 mg carbamazepine (tablets) the mean peak concentration of unchanged carbamazepine in the plasma is approx. 4.5 μg/ml.
The bioavailability of Carbamazepine in various oral formulations has been shown to lie between 85-100%.
Ingestion of food has no significant influence on the rate and extent of absorption, regardless of the dosage form of Carbamazepine.
Steady-state plasma concentrations of carbamazepine are attained within about 1-2 weeks, depending individually upon auto-induction by carbamazepine and hetero-induction by other enzyme-inducing drugs, as well as on pre-treatment status, dosage, and duration of treatment.
Different preparations of carbamazepine may vary in bioavailability; to avoid reduced effect or risk of breakthrough seizures or excessive side effects, it may be prudent to avoid changing the formulation.
Distribution: Carbamazepine is bound to serum proteins to the extent of 70-80%. The concentration of unchanged substance in cerebrospinal fluid and saliva reflects the non-protein bound portion in plasma (20-30%). Concentrations in breast milk were found to be equivalent to 25-60% of the corresponding plasma levels.
Carbamazepine crosses the placental barrier. Assuming complete absorption of carbamazepine, the apparent volume of distribution ranges from 0.8 to 1.9 L/kg.
Metabolism: Carbamazepine is metabolized in the liver, where the epoxide pathway of biotransformation is the most important one, yielding the 10, 11-transdiol derivative and its glucuronide as the main metabolites.
Cytochrome P450 3A4 has been identified as the major isoform responsible for the formation of carbamazepine 10, 11-epoxide from carbamazepine. Human microsomal epoxide hydrolase has been identified as the enzyme responsible for the formation of the 10, 11-transdiol derivative from carbamazepine-10, 11 epoxide. 9-Hydroxy-methyl-10-carbamoyl acridan is a minor metabolite related to this pathway. After a single oral dose of carbamazepine about 30% appears in the urine as end-products of the epoxide pathway.
Other important biotransformation pathways for carbamazepine lead to various monohydroxylated compounds, as well as to the N-glucuronide of carbamazepine produced by UGT2B7.
Elimination: The elimination half-life of unchanged carbamazepine averages approx. 36 hours following a single oral dose, whereas after repeated administration it averages only 16-24 hours (auto-induction of the hepatic mono-oxygenase system), depending on the duration of the medication. In patients receiving concomitant treatment with other enzyme-inducing drugs (e.g. phenytoin, phenobarbitone), half-life values averaging 9-10 hours have been found.
The mean elimination half-life of the 10, 11-epoxide metabolite in the plasma is about 6 hours following single oral doses of the epoxide itself.
After administration of a single oral dose of 400 mg carbamazepine, 72% is excreted in the urine and 28% in the faeces. In the urine, about 2% of the dose is recovered as unchanged drug and about 1% as the pharmacologically active 10, 11-epoxide metabolite.
Characteristics in patients: The steady-state plasma concentrations of carbamazepine considered as "therapeutic range" vary considerably inter-individually; for the majority of patients a range between 4-12 μg/ml corresponding to 17-50 μmol/l has been reported. Concentrations of carbamazepine 10, 11-epoxide (pharmacologically active metabolite): about 30% of carbamazepine levels.
Owing to enhanced carbamazepine elimination, children may require higher doses of carbamazepine (in mg/kg) than adults to maintain therapeutic concentrations.
There is no indication of altered pharmacokinetics of carbamazepine in elderly patients as compared with young adults.
No data are available on the pharmacokinetics of carbamazepine in patients with impaired hepatic or renal function.

Mezacar is indicated to control secondarily generalized tonic-clonic seizures and partial seizures. It is also used in the treatment of trigeminal neuralgia and has been tried with variable success in glossopharyngeal neuralgia and other severe pain syndromes associated with neurological disorders such as tabes dorsalis and multiple sclerosis. Another use is in the prophylaxis of manic depression (bipolar disorder) unresponsive to lithium.

Before deciding to initiate treatment, patients of Han Chinese and Thai origin should whenever possible be screened for HLA-B*1502 as this allele strongly predicts the risk of severe carbamazepine-associated Stevens-Johnson syndrome.
Epilepsy: The dose of carbamazepine should be adjusted to the needs of the individual patient to achieve adequate control of seizures. Determination of plasma levels may help in establishing the optimum dosage. In the treatment of epilepsy, the dose of carbamazepine usually requires total plasma-carbamazepine concentrations of about 4 to 12 micrograms/mL (17 to 50 micromoles/litre) (see Precautions).
Adults: It is advised that with all formulations of Mezacar, a gradually increasing dosage scheme is used and this should be adjusted to suit the needs of the individual patient.
Mezacar should be taken in a number of divided doses although initially 100-200 mg once or twice daily is recommended. This may be followed by a slow increase until the best response is obtained, often 800-1200 mg daily. In some instances, 1600 mg or even 2000 mg daily may be necessary.
Elderly: Due to the potential for drug interactions, the dosage of Mezacar should be selected with caution in elderly patients.
Children and adolescents: It is advised that with all formulations of Mezacar, a gradually increasing dosage scheme is used and this should be adjusted to suit the needs of the individual patient.
Usual dosage 10-20 mg/kg bodyweight daily taken in several divided doses.
Mezacar tablets are not recommended for very young children.
5-10 years: 400 to 600 mg daily (2-3 x 200 mg tablets per day, to be taken in divided doses).
10-15 years: 600 to 1000 mg daily (3-5 x 200 mg tablets per day, to be taken in several divided doses).
>15 years of age: 800 to 1200 mg daily (same as adult dose).
Maximum recommended dose: Up to 6 years of age: 35 mg/kg/day; 6-15 years of age: 1000 mg/day; >15 years of age: 1200 mg/day.
Wherever possible, anti-epileptic agents should be prescribed as the sole antiepileptic agent but if used in polytherapy the same incremental dosage pattern is advised.
When Mezacar is added to existing antiepileptic therapy, this should be done gradually while maintaining or, if necessary, adapting the dosage of the other antiepileptic(s) (see Interactions).
Trigeminal neuralgia: Slowly raise the initial dosage of 200-400 mg daily until freedom from pain is achieved (normally at 200 mg 3-4 times daily). In the majority of patients a dosage of 200 mg 3 or 4 times a day is sufficient to maintain a pain free state. In some instances, doses of 1600 mg Mezacar daily may be needed. However, once the pain is in remission, the dosage should be gradually reduced to the lowest possible maintenance level. Maximum recommended dose is 1200 mg/day. When pain relief has been obtained, attempts should be made to gradually discontinue therapy, until another attack occurs.
Elderly: Dosage in Trigeminal neuralgia: Due to drug interactions and different antiepileptic drug pharmacokinetics, the dosage of Mezacar should be selected with caution in elderly patients.
In elderly patients, an initial dose of 100 mg twice daily is recommended. The initial dosage of 100 mg twice daily should be slowly raised daily until freedom from pain is achieved (normally at 200 mg 3 to 4 times daily). The dosage should then be gradually reduced to the lowest possible maintenance level. Maximum recommended dose is 1200 mg/day. When pain relief has been obtained, attempts should be made to gradually discontinue therapy, until another attack occurs.
For the prophylaxis of manic depressive psychosis in patients unresponsive to lithium therapy: Initial starting dose of 400 mg daily, in divided doses, increasing gradually until symptoms are controlled or a total of 1600 mg given in divided doses is reached. The usual dosage range is 400-600 mg daily, given in divided doses.
Special populations: Renal impairment/Hepatic impairment: No data are available on the pharmacokinetics of carbamazepine in patients with impaired hepatic or renal function.
Method of administration: Mezacar is given orally, usually in two or three divided doses. Mezacar may be taken during, after or between meals, with a little liquid e.g. a glass of water.

Symptoms: The presenting signs and symptoms of overdosage involve the central nervous, cardiovascular, respiratory systems and the adverse drug reactions mentioned previously.
Central nervous system: CNS depression; disorientation, depressed level of consciousness, somnolence, agitation, hallucination, coma; blurred vision, slurred speech, dysarthria, nystagmus, ataxia, dyskinesia, initially hyperreflexia, later hyporeflexia; convulsions, psychomotor disturbances, myoclonus, hypothermia, mydriasis.
Respiratory system: Respiratory depression, pulmonary oedema.
Cardiovascular system: Tachycardia, hypotension and at times hypertension, conduction disturbance with widening of QRS complex; syncope in association with cardiac arrest.
Gastro-intestinal system: Vomiting, delayed gastric emptying reduced bowel motility.
Musculoskeletal system: There have been some cases which reported rhabdomyolysis in association with carbamazepine toxicity.
Renal function: Retention of urine, oliguria or anuria; fluid retention, water intoxication due to ADH-like effect of carbamazepine.
Laboratory findings: Hyponatraemia, possibly metabolic acidosis, possibly hyperglycaemia, increased muscle creatine phosphokinase.
Treatment: There is no specific antidote.
Management should initially be guided by the patient's clinical condition; admission to hospital. Measurement of the plasma level to confirm carbamazepine poisoning and to ascertain the size of the overdose.
Evacuation of the stomach, gastric lavage, and administration of activated charcoal. Delay in evacuating the stomach may result in delayed absorption, leading to relapse during recovery from intoxication. Supportive medical care in an intensive care unit with cardiac monitoring and careful correction of electrolyte imbalance.
Special recommendations: Charcoal haemoperfusion has been recommended. Hemodialysis is the effective treatment modality in the management of the carbamazepine overdose.
Relapse and aggravation of symptomatology on the 2nd and 3rd day after overdose, due to delayed absorption, should be anticipated.

Known hypersensitivity to carbamazepine or structurally related drugs (e.g. tricyclic antidepressants) or any other component of the formulation.
Patients with atrioventricular block, a history of bone marrow depression or a history of hepatic porphyrias (e.g. acute intermittent porphyria, variegate porphyria, porphyria cutanea tarda).
The use of Mezacar is contraindicated in combination with monoamine oxidase inhibitors (MAOIs).

Serious Dermatologic Reactions and HLA-B*1502 Allele: Serious and sometimes fatal dermatologic reactions, including toxic epidermal necrolysis (TEN) and Stevens-Johnson Syndrome (SJS), have been reported during treatment with Carbamazepine. These reactions are estimated to occur in 1 to 6 per 10,000 new users in countries with mainly Caucasian populations, but the risk in some Asian countries is estimated to be about 10 times higher. Studies in patients of Chinese ancestry have found a strong association between the risk of developing SJS/TEN and the presence of HLA-B*1502, an inherited allelic variant of the HLA-B gene. HLA-B*1502 is found almost exclusively in patients with ancestry across broad areas of Asia. Patients with ancestry in genetically at-risk populations should be screened for the presence of HLA-B*1502 prior to initiating treatment with Mezacar. Patients testing positive for the allele should not be treated with Mezacar unless the benefit clearly outweighs the risk (see Precautions).
Aplastic Anemia and Agranulocytosis: Aplastic anemia and agranulocytosis have been reported in association with the use of Carbamazepine. Data from a population-based case control study demonstrate that the risk of developing these reactions is 5 to 8 times greater than in the general population. However, the overall risk of these reactions in the untreated general population is low, approximately six patients per one million population per year for agranulocytosis and two patients per one million populations per year for aplastic anemia.
Although reports of transient or persistent decreased platelet or white blood cell counts are not uncommon in association with the use of Carbamazepine, data are not available to estimate accurately their incidence or outcome. However, the vast majority of the cases of leukopenia have not progressed to the more serious conditions of aplastic anemia or agranulocytosis.
Because of the very low incidence of agranulocytosis and aplastic anemia, the vast majority of minor hematologic changes observed in monitoring of patients on Carbamazepine are unlikely to signal the occurrence of either abnormality. Nonetheless, complete pretreatment hematological testing should be obtained as a baseline. If a patient in the course of treatment exhibits low or decreased white blood cell or platelet counts, the patient should be monitored closely. Discontinuation of the drug should be considered if any evidence of significant bone marrow depression develops.

Warnings: Agranulocytosis and aplastic anaemia have been associated with Carbamazepine; however, due to the very low incidence of these conditions, meaningful risk estimates for Carbamazepine are difficult to obtain. The overall risk in the general untreated population has been estimated at 4.7 persons per million per year for agranulocytosis and 2.0 persons per million per year for aplastic anaemia.
Decreased platelet or white blood cell counts occur occasionally to frequently in association with the use of Carbamazepine. Nonetheless, complete pre-treatment blood counts, including platelets and possibly reticulocytes and serum iron, should be obtained as a baseline, and periodically thereafter.
Patients and their relatives should be made aware of early toxic signs and symptoms indicative of a potential haematological problem, as well as symptoms of dermatological or hepatic reactions. If reactions such as fever, sore throat, rash, ulcers in the mouth, easy bruising, petechial or purpuric haemorrhage appear, the patient should be advised to consult his physician immediately.
If the white blood cell or platelet count is definitely low or decreased during treatment, the patient and the complete blood count should be closely monitored. However, treatment with Mezacar should be discontinued if the patient develops leucopenia which is severe, progressive or accompanied by clinical manifestations, e.g. fever or sore throat. Mezacar should also be discontinued if any evidence of significant bone marrow depression appears. Liver function tests should also be performed before commencing treatment and periodically thereafter, particularly in patients with a history of liver disease and in elderly patients. The drug should be withdrawn immediately in cases of aggravated liver dysfunction or acute liver disease.
Some liver function tests in patients receiving carbamazepine may be found to be abnormal, particularly gamma glutamyl transferase. This is probably due to hepatic enzyme induction. Enzyme induction may also produce modest elevations in alkaline phosphatase. These enhancements of hepatic metabolising capacity are not an indication for the withdrawal of carbamazepine.
Severe hepatic reactions to carbamazepine occur very rarely. The development of signs and symptoms of liver dysfunction or active liver disease should be urgently evaluated and treatment with Mezacar suspended pending the outcome of the evaluation.
Suicidal ideation and behaviour have been reported in patients treated with anti-epileptic agents in several indications. A meta-analysis of randomised placebo controlled trials of anti-epileptic drugs has also shown a small increased risk of suicidal ideation and behaviour. The mechanism of this risk is not known and the available data do not exclude the possibility of an increased risk for carbamazepine. Therefore patients should be monitored for signs of suicidal ideation and behaviours and appropriate treatment should be considered. Patients (and caregivers of patients) should be advised to seek medical advice should signs of suicidal ideation or behaviour emerge.
Serious dermatological reactions, including toxic epidermal necrolysis (TEN: also known as Lyell's syndrome) and Stevens Johnson syndrome (SJS) have been reported very rarely with Carbamazepine. Patients with serious dermatological reactions may require hospitalization, as these conditions may be life-threatening and may be fatal. Most of the SJS/TEN cases appear in the first few months of treatment with Carbamazepine. These reactions are estimated to occur in 1 to 6 per 10,000 new users in countries with mainly Caucasian populations. If signs and symptoms suggestive of severe skin reactions (e.g. SJS, Lyell's syndrome/TEN) appear, Mezacar should be withdrawn at once and alternative therapy should be considered.
Cutaneous reactions: Serious and sometimes fatal cutaneous reactions including toxic epidermal necrolysis (TEN) and Stevens-Johnson syndrome (SJS) have been reported during treatment with carbamazepine. These reactions are estimated to occur in 1-6 per 10 000 new users in countries with mainly Caucasian populations, but the risk in some Asian countries is estimated to be about 10 times higher.
There is growing evidence of the role of different HLA alleles in predisposing patients to immune-mediated adverse reactions.
HLA-B*1502 allele - in Han Chinese, Thai and other Asian populations: HLA-B* 1502 in individuals of Han Chinese and Thai origin has been shown to be strongly associated with the risk of developing Stevens-Johnson syndrome (SJS) when treated with carbamazepine. The prevalence of HLA-B*1502 carrier is about 10% in Han Chinese and Thai populations. Whenever possible, these individuals should be screened for this allele before starting treatment with carbamazepine. If these individuals test positive, carbamazepine should not be started unless there is no other therapeutic option. Tested patients who are found to be negative for HLA-B* 1502 have a low risk of SJS, although the reactions may still very rarely occur.
There are some data that suggest an increased risk of serious carbamazepine-associated TEN/SJS in other Asian populations. Because of the prevalence of this allele in other Asian populations (e.g. above 15% in the Philippines and Malaysia), testing genetically at risk populations for the presence of HLA-B*1502 may be considered.
The prevalence of the HLA-B*1502 allele is negligible in e.g. European descent, African, Hispanic populations sampled, and in Japanese and Koreans (< 1%).
HLA-A*3101 allele - European descent and Japanese populations: There are some data that suggest HLA-A*3101 is associated with an increased risk of carbamazepine induced cutaneous adverse drug reactions including SJS, TEN, Drug rash with eosinophilia (DRESS), or less severe acute generalized exanthematous pustulosis (AGEP) and maculopapular rash in people of European descent and the Japanese.
The frequency of the HLA-A*3101 allele varies widely between ethnic populations. HLA-A*3101 allele has a prevalence of 2 to 5% in European populations and about 10% in Japanese population.
The presence of HLA-A*3101 allele may increase the risk for carbamazepine induced cutaneous reactions (mostly less severe) from 5.0% in general population to 26.0% among subjects of Northern European ancestry, whereas its absence may reduce the risk from 5.0% to 3.8%.
There are insufficient data supporting a recommendation for HLA-A*3101 screening before starting carbamazepine treatment.
If patients of European descent or Japanese origin are known to be positive for HLAA* 3101 allele, the use of carbamazepine may be considered if the benefits are thought to exceed risks.
Other dermatologic reactions: Mild skin reactions e.g. isolated macular or maculopapular exanthema, can also occur and are mostly transient and not hazardous. They usually disappear within a few days or weeks, either during the continued course of treatment or following a decrease in dosage. However, since it may be difficult to differentiate the early signs of more serious skin reactions from mild transient reactions, the patient should be kept under close surveillance with consideration given to immediately withdrawing the drug should the reaction worsen with continued use.
The HLA-B*1502 allele has not been found to predict risk of less severe adverse cutaneous reactions from carbamazepine, such as anticonvulsant hypersensitivity syndrome or non-serious rash (maculopapular eruption).
Hypersensitivity: Carbamazepine may trigger hypersensitivity reactions, including Drug Rash with Eosinophilia and Systemic Symptoms (DRESS), reactivation of HHV6 associated with DRESS, a delayed multi-organ hypersensitivity disorder with fever, rash, vasculitis, lymphadenopathy, pseudo lymphoma, arthralgia, leukopenia, eosinophilia, hepato-splenomegaly, abnormal liver function tests and vanishing bile duct syndrome (destruction and disappearance of the intrahepatic bile ducts), that may occur in various combinations. Other organs may also be affected (e.g. lungs, kidneys, pancreas, myocardium, colon).
In general, if signs and symptoms suggestive of hypersensitivity reactions occur, Mezacar should be withdrawn immediately.
Patients who have exhibited hypersensitivity reactions to carbamazepine should be informed that 25-30 % of these patients may experience hypersensitivity reactions with oxacarbazepine.
Cross-hypersensitivity can occur between carbamazepine and phenytoin.
Mezacar should be used with caution in patients with mixed seizures which include absences, either typical or atypical. In all these conditions, Mezacar exacerbate seizures. In case of exacerbation of seizures, Mezacar should be discontinued.
An increase in seizure frequency may occur during switchover from an oral formulation to suppositories.
Dose reduction and withdrawal effects: Abrupt withdrawal of Mezacar may precipitate seizures therefore carbamazepine withdrawal should be gradual. If treatment with Mezacar has to be withdrawn abruptly in a patient with epilepsy, the changeover to another anti-epileptic drug should if necessary be affected under the cover of a suitable drug.
Endocrinological effects: Breakthrough bleeding has been reported in women taking Carbamazepine while using hormonal contraceptives. The reliability of hormonal contraceptives may be adversely affected by Carbamazepine and women of childbearing potential should be advised to consider using alternative forms of birth control while taking Carbamazepine.
Patients taking Mezacar requiring hormonal contraception should receive a preparation containing not less than 50 μg oestrogen or use of some alternative non-hormonal method of contraception should be considered.
Monitoring of plasma levels: Although correlations between dosages and plasma levels of carbamazepine, and between plasma levels and clinical efficacy or tolerability are rather tenuous, monitoring of the plasma levels may be useful in the following conditions: dramatic increase in seizure frequency/verification of patient compliance; during pregnancy; when treating children or adolescents; in suspected absorption disorders; in suspected toxicity when more than one drug is being used (see Interactions).
Precautions: Carbamazepine should be prescribed only after a critical benefit-risk appraisal and under close monitoring in patients with a history of cardiac, hepatic or renal damage, adverse haematological reactions to other drugs, or interrupted courses of therapy with Carbamazepine.
Baseline and periodic complete urinalysis and BUN determinations are recommended.
Hyponatremia: Hyponatremia is known to occur with carbamazepine. In patients with pre-existing renal conditions associated with low sodium or in patients treated concomitantly with sodium-lowering medicinal products (e.g. diuretics, medicinal products associated with inappropriate ADH secretion), serum sodium levels should be measured prior to initiating carbamazepine therapy. Thereafter, serum sodium levels should be measured after approximately two weeks and then at monthly intervals for the first three months during therapy, or according to clinical need. These risk factors may apply especially to elderly patients. If hyponatraemia is observed, water restriction is an important counter-measurement if clinically indicated.
Hypothyroidism: Carbamazepine may reduce serum concentrations of thyroid hormones through enzyme induction requiring an increase in dose of thyroid replacement therapy in patients with hypothyroidism. Hence thyroid function monitoring is suggested to adjust the dosage of thyroid replacement therapy.
Anticholinergic effects: Carbamazepine has shown mild anticholinergic activity; patients with increased intraocular pressure and urinary retention should therefore be closely observed during therapy.
Psychiatric effects: The possibility of activation of a latent psychosis and, in elderly patients, of confusion or agitation should be borne in mind.
Interactions: Co-administration of inhibitors of CYP3A4 or inhibitors of epoxide hydrolase with carbamazepine can induce adverse reactions (increase of carbamazepine or carbamazepine-10, 11 epoxide plasma concentrations respectively). The dosage of Mezacar should be adjusted accordingly and/or the plasma levels monitored.
Co-administration of CYP3A4 inducers with carbamazepine may decrease carbamazepine plasma concentrations and its therapeutic effect, while discontinuation of a CYP3A4 inducer may increase carbamazepine plasma concentrations. The dosage of Mezacar may have to be adjusted.
Carbamazepine is a potent inducer of CYP3A4 and other phase I and phase II enzyme systems in the liver, and may therefore reduce plasma concentrations of co-medications mainly metabolized by CYP3A4 by induction of their metabolism.
Female patients of childbearing potential should be warned that the concurrent use of Mezacar with hormonal contraceptives may render this type of contraceptive ineffective. Alternative non-hormonal forms of contraception are recommended when using Mezacar.
Effects on Ability to Drive and Use Machines: The patient's ability to react may be impaired by the medical condition resulting in seizures and adverse reactions including dizziness, drowsiness, ataxia, diplopia, impaired accommodation, and blurred vision reported with Carbamazepine, especially at the start of treatment or in connection with dose adjustments. Patients should therefore exercise due caution when driving a vehicle or operating machinery.

Pregnancy: Offspring of epileptic mothers with untreated epilepsy are known to be more prone to developmental disorders, including malformations. Developmental disorders and malformations, including spina bifida, and also other congenital anomalies e.g. craniofacial defects such as cleft lip/palate, cardiovascular malformations, hypospadias and anomalies involving various body systems, have been reported in association with the use of Carbamazepine. Patients should be counselled regarding the possibility of an increased risk of malformations and given the opportunity of antenatal screening. Based on data in a North American pregnancy registry, the rate of major congenital malformations, defined as a structural abnormality with surgical, medical, or cosmetic importance, diagnosed within 12 weeks of birth was 3.0% (95% CI 2.1 to 4.2%) among mothers exposed to carbamazepine monotherapy in the first trimester and 1.1% (95% CI 0.35 to 2.5%) among pregnant women not taking any antiepileptic drug (relative risk 2.7, 95% CI 1.1 to 7.0).
Taking these data into consideration: Pregnant women with epilepsy should be treated with special care.
If women receiving Mezacar become pregnant or plan to become pregnant, or if the problem of initiating treatment with Mezacar arises during pregnancy, the drug's expected benefits must be carefully weighed against its possible hazards, particularly in the first 3 months of pregnancy.
In women of childbearing potential Mezacar should, wherever possible, be prescribed as monotherapy, because the incidence of congenital abnormalities in the offspring of women treated with a combination of antiepileptic drugs is greater than in those of mothers receiving the individual drugs as monotherapy. The risk of malformations following exposure to carbamazepine as polytherapy may vary depending on the specific drugs used and may be higher in polytherapy combinations that include valproate.
Minimum effective doses should be given and monitoring of plasma levels is recommended. The plasma concentration could be maintained in the lower side of the therapeutic range 4 to 12 micrograms/mL provided seizure control is maintained. There is evidence to suggest that the risk of malformation with carbamazepine may be dose-dependent i.e. at a dose <400 mg per day, the rates of malformation were lower than with higher doses of carbamazepine.
Patients should be counseled regarding the possibility of an increased risk of malformations and given the opportunity of antenatal screening.
During pregnancy, an effective antiepileptic treatment should not be interrupted, since the aggravation of the illness is detrimental to both the mother and the fetus.
Monitoring and prevention: Folic acid deficiency is known to occur in pregnancy. Antiepileptic drugs have been reported to aggravate deficiency. This deficiency may contribute to the increased incidence of birth defects in the offspring of treated epileptic women. Folic acid supplementation has therefore been recommended before and during pregnancy.
In the neonate: In order to prevent bleeding disorders in the offspring, it has also been recommended that vitamin K₁, be given to the mother during the last weeks of pregnancy as well as to the neonate.
There have been a few cases of neonatal seizures and/or respiratory depression associated with maternal Carbamazepine and other concomitant antiepileptic drug use. A few cases of neonatal vomiting, diarrhoea and/or decreased feeding have also been reported in association with maternal Carbamazepine use. These reactions may represent a neonatal withdrawal syndrome.
Women of child-bearing potential and contraceptive measures: Due to enzyme induction, Carbamazepine may result in a failure of the therapeutic effect of oral contraceptive drugs containing oestrogen and/or progesterone. Women of child bearing potential should be advised to use alternative contraceptive methods while on treatment with Carbamazepine.
Breast-feeding: Carbamazepine passes into the breast milk (about 25-60% of the plasma concentrations). The benefits of breast-feeding should be weighed against the remote possibility of adverse effects occurring in the infant. Mothers taking Carbamazepine may breast-feed their infants, provided the infant is observed for possible adverse reactions (e.g. excessive somnolence, allergic skin reaction). There have been some reports of cholestatic hepatitis in neonates exposed to carbamazepine during antenatal and or during breast feeding. Therefore, breast-fed infants of mothers treated with carbamazepine should be carefully observed for adverse hepatobiliary effects.
Fertility: There have been very rare reports of impaired male fertility and/or abnormal spermatogenesis.

Summary of the safety profile: Particularly at the start of treatment with Carbamazepine, or if the initial dosage is too high, or when treating elderly patients, certain types of adverse reaction occur very commonly or commonly, e.g. CNS adverse reactions (dizziness, headache, ataxia, drowsiness, fatigue, diplopia); gastrointestinal disturbances (nausea, vomiting), as well as allergic skin reactions.
The dose-related adverse reactions usually abate within a few days, either spontaneously or after a transient dosage reduction. The occurrence of CNS adverse reactions may be a manifestation of relative overdosage or significant fluctuation in plasma levels. In such cases it is advisable to monitor the plasma levels and divide the daily dosage into smaller (i.e. 3-4) fractional doses.
Summary of adverse drug reactions compiled from clinical trials and from spontaneous reports: Adverse drug reactions from clinical trials are listed by MedDRA system organ class. Within each system organ class, the adverse drug reactions are ranked by frequency, with the most frequent reactions first. Within each frequency grouping, adverse drug reactions are presented in order of decreasing seriousness. In addition, the corresponding frequency category for each adverse drug reaction is based on the following convention (CIOMS III): very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000).
Blood and lymphatic system disorders: Very common: Leucopenia.
Common: Thrombocytopenia, eosinophilia.
Rare: Leucocytosis, lymphadenopathy.
Very rare: Agranulocytosis, aplastic anaemia, pancytopenia, aplasia pure red cell, anaemia, anaemia megaloblastic, reticulocytosis, haemolytic anaemia.
Not known: Bone marrow depression.
Immune system disorders: Rare: A delayed multi-organ hypersensitivity disorder with fever, rashes, vasculitis, lymphadenopathy, pseudo lymphoma, arthralgia, leucopenia, eosinophilia, hepato-splenomegaly, abnormal liver function tests and vanishing bile duct syndrome (destruction and disappearance of the intrahepatic bile ducts) occurring in various combinations. Other organs may also be affected (e.g. liver, lungs, kidneys, pancreas, myocardium, colon).
Very rare: Anaphylactic reaction, oedema angioedema, hypogammaglobulinaemia.
Not known**: Drug Rash with Eosinophilia and Systemic Symptoms (DRESS).
Infections and infestations: Not known**: Reactivation of Human herpes virus 6 infection.
Endocrine disorders: Common: Oedema, fluid retention, weight increase, hyponatraemia and blood osmolarity decreased due to an antidiuretic hormone (ADH)-like effect, leading in rare cases to water intoxication accompanied by lethargy, vomiting, headache, confusional state, neurological disorders.
Very rare: Galactorrhoea, gynaecomastia.
Metabolism and nutrition disorders: Rare: Folate deficiency, decreased appetite.
Very rare: Porphyria acute (acute intermittent porphyria and variegate porphyria), porphyria non-acute (porphyria cutanea tarda).
Psychiatric disorders: Rare: Hallucinations (visual or auditory), depression, aggression, agitation, restlessness, confusional state.
Very rare: Activation of psychosis.
Nervous system disorders: Very common: Ataxia, dizziness, somnolence.
Common: Diplopia, headache.
Uncommon: Abnormal involuntary movements (e.g. tremor, asterixis, dystonia, tics), nystagmus.
Rare: Dyskinesia, eye movement disorder, speech disorders (e.g. dysarthria or slurred speech), choreoathetosis, neuropathy peripheral, paraesthesia, and paresis.
Very rare: Neuroleptic malignant syndrome, aseptic meningitis with myoclonus and peripheral eosinophilia, dysgeusia.
Not known**: Sedation, memory impairment.
Eye disorders: Common: Accommodation disorders (e.g. blurred vision).
Very rare: Lenticular opacities, conjunctivitis.
Ear and Labyrinth disorders: Very rare: Hearing disorders, e.g. tinnitus, hyperacusis, hypoacusis, change in pitch perception.
Cardiac disorders: Rare: Cardiac conduction disorders.
Very rare: Arrhythmia, atrioventricular block with syncope, bradycardia, cardiac failure congestive, coronary artery disease aggravated.
Vascular disorders: Rare: Hypertension or hypotension.
Very rare: Circulatory collapse, embolism (e.g. pulmonary embolism), thrombophlebitis.
Respiratory, thoracic and mediastinal disorders: Very rare: Pulmonary hypersensitivity characterized e.g. by fever, dyspnea, pneumonitis or pneumonia.
Gastrointestinal disorders: Very common: Vomiting, nausea.
Common: Dry mouth, with suppositories rectal irritation may occur.
Uncommon: Diarrhea, constipation.
Rare: Abdominal pain.
Very rare: Pancreatitis, glossitis, stomatitis.
Not known: Colitis.
Hepatobiliary disorders: Rare: Hepatitis of cholestatic, parenchymal (hepatocellular) or mixed type, vanishing bile duct syndrome, jaundice.
Very rare: Hepatic failure, granulomatous liver disease.
Skin and subcutaneous tissue disorders: Very common: Urticaria, which may be severe dermatitis allergic.
Uncommon: Dermatitis exfoliative.
Rare: Systemic lupus erythematosus, pruritus.
Very rare: Stevens-Johnson syndrome*, toxic epidermal necrolysis, photosensitivity reaction, erythema multiforme, erythema nodosum, pigmentation disorder, purpura, acne, hyperhidrosis, alopecia, hirsutism.
Not known**: Acute Generalized Exanthematous Pustulosis (AGEP)**, lichenoid keratosis, onychomadesis.
Musculoskeletal and connective tissue disorders: Rare: Muscular weakness.
Very rare: Bone metabolism disorders (decrease in plasma calcium and blood 25-hydroxy-cholecalciferol) leading to osteomalacia/osteoporosis, arthralgia, myalgia, muscle spasms.
Not known**: Fracture.
Renal and urinary disorders: Very rare: Sexual disturbances/erectile dysfunction spermatogenesis abnormal(with decreased sperm count and/or motility).
General disorders and administration site conditions: Very common: Fatigue.
Investigations: Very common: Gamma-glutamyltransferase increased (due to hepatic enzyme induction), usually not clinically relevant.
Common: Blood alkaline phosphatase increased.
Uncommon: Transaminases increased.
Rare: Systemic lupus erythematosus, pruritus.
Very rare: Intraocular pressure increased, blood cholesterol increased, high density lipoprotein increased, blood triglycerides increased. Thyroid function test abnormal: decreased L-Thyroxin (free thyroxine, thyroxine, tri-iodothyronine) and increased blood thyroid stimulating hormone, usually without clinical manifestations, blood prolactin increased.
Not known**: Bone density decreased.
* In some Asian countries also reported as rare.
**Additional adverse drug reactions from spontaneous reports (frequency not known).
The following adverse drug reactions have been derived from post-marketing experience with Carbamazepine via spontaneous case reports and literature cases. Because these reactions are reported voluntarily from a population of uncertain size, it is not possible to reliably estimate their frequency which is therefore categorized as not known. Adverse drug reactions are listed according to system organ classes in MedDRA. Within each system organ class, ADRs are presented in order of decreasing seriousness.
There have been reports of decreased bone mineral density, osteopenia, osteoporosis and fractures in patients on long-term therapy with carbamazepine. The mechanism by which carbamazepine affects bone metabolism has not been identified.
There is increasing evidence regarding the association of genetic markers and the occurrence of cutaneous ADRs such as SJS, TEN, DRESS, AGEP and maculopapular rash. In Japanese and European patients, these reactions have been reported to be associated with the use of carbamazepine and the presence of the HLA-A*3101 allele. Another marker, HLA-B*1502 has been shown to be strongly associated with SJS and TEN among individuals of Han Chinese, Thai and some other Asian ancestry.

Cytochrome P450 3A4 (CYP 3A4) is the main enzyme catalysing formation of the active metabolite carbamazepine 10, 11-epoxide. Co-administration of inhibitors of CYP 3A4 may result in increased carbamazepine plasma concentrations which could induce adverse reactions. Co-administration of CYP 3A4 inducers might increase the rate of carbamazepine metabolism, thus leading to potential decreases in the carbamazepine serum level and therapeutic effect.
Similarly, discontinuation of a CYP3A4 inducer may decrease the rate of metabolism of carbamazepine, leading to an increase in carbamazepine plasma levels.
Carbamazepine is a potent inducer of CYP3A4 and other phase I and phase II enzyme systems in the liver, and may therefore reduce plasma concentrations of comedications mainly metabolized by CYP3A4 by induction of their metabolism.
Human microsomal epoxide hydrolase has been identified as the enzyme responsible for the formation of the 10,11-transdiol derivative from carbamazepine-10,11 epoxide. Co-administration of inhibitors of human microsomal epoxide hydrolase may result in increased carbamazepine-10,11 epoxide plasma concentrations.
Interactions resulting in a contraindication: The use of Mezacar is contraindicated in combination with monoamine-oxidase inhibitors (MAOIs); before administering Mezacar MAOIs should be discontinued for a minimum of 2 weeks, or longer if the clinical situation permits (see Contraindications).
Agents that may raise carbamazepine plasma levels: Since raised plasma carbamazepine levels may result in adverse reactions (e.g. dizziness, drowsiness, ataxia, diplopia), the dosage of Mezacar should be adjusted accordingly and/or the plasma levels monitored when used concomitantly with the substances described as follows: Analgesics, anti-inflammatory drugs: Dextropropoxyphene.
Androgens: Danazol.
Antibiotics: Macrolide antibiotics (e.g. erythromycin, clarithromycin), ciprofloxacin.
Antidepressants: Fluoxetine, fluvoxamine, paroxetine, trazodone.
Antiepileptics: Vigabatrin.
Antifungals: Azoles (e.g. itraconazole, ketoconazole, fluconazole, voriconazole). Alternative anti-convulsants may be recommended in patients treated with voriconazole or itraconazole.
Antihistamines: Loratadine.
Antipsychotics: Olanzapine.
Antituberculosis: Isoniazid.
Antivirals: Protease inhibitors for HIV treatment (e.g. ritonavir).
Carbonic anhydrase inhibitors: Acetazolamide.
Cardiovascular drugs: Diltiazem, verapamil.
Gastrointestinal drugs: Possibly cimetidine, omeprazole.
Other interactions: Grapefruit juice, nicotinamide (only in high dosage).
Agents that may raise the active metabolite carbamazepine-10,11-epoxide plasma levels: Since raised plasma carbamazepine-10,11-epoxide levels may result in adverse reactions (e.g. dizziness, drowsiness, ataxia, diplopia), the dosage of Mezacar should be adjusted accordingly and/or the plasma levels monitored when used concomitantly with the substances described as follows: Quetiapine, primidone, progabide, valproic acid, valnoctamide and valpromide.
Agents that may decrease carbamazepine plasma levels: The dose of Mezacar may have to be adjusted when used concomitantly with the substances described as follows: Antiepileptics: Oxcarbazepine, phenobarbital, phenytoin (to avoid phenytoin intoxication and subtherapeutic concentrations of carbamazepine it is recommended to adjust the plasma concentration of phenytoin to 13 micrograms /mL before adding carbamazepine to the treatment) and fosphenytoin, primidone, and, although the data are partly contradictory, possibly also clonazepam.
Antineoplastics: Cisplatin or doxorubicin.
Antituberculosis: Rifampicin.
Bronchodilatators or anti-asthma drugs: Theophylline, aminophylline.
Dermatological drugs: Isotretinoin.
Other interactions: Herbal preparations containing St John's wort (Hypericum perforatum).
Effect of Carbamazepine on plasma levels of concomitant agents: Carbamazepine may lower the plasma level, diminish or even abolish the activity of certain drugs. The dosage of the following drugs may have to be adjusted to clinical requirement: Analgesics, anti-inflammatory agents: Buprenorphine, methadone, paracetamol (long term administration of carbamazepine and paracetamol (acetaminophen) may be associated with hepatotoxicity), tramadol.
Antibiotics: Doxycycline, rifabutin.
Anticoagulants: Oral anticoagulants (e.g. warfarin and acenocoumarol).
Antidepressants: Bupropion, citalopram, mianserin, sertraline, trazodone, tricyclic antidepressants (e.g. imipramine, amitriptyline, nortriptyline, clomipramine).
Antiemetics: Aprepitant.
Antiepileptics: Clobazam, clonazepam, ethosuximide, lamotrigine, oxcarbazepine, primidone, tiagabine, topiramate, valproic acid, zonisamide. To avoid phenytoin intoxication and subtherapeutic concentrations of carbamazepine it is recommended to adjust the plasma concentration of phenytoin to 13 micrograms /mL before adding carbamazepine to the treatment. There have been rare reports of an increase in plasma mephenytoin levels.
Antifungals: Itraconazole, voriconazole. Alternative anti-convulsants may be recommended in patients treated with voriconazole or itraconazole.
Anthelminthics: Albendazole.
Antineoplastics: Imatinib, cyclophosphamide, lapatinib, temsirolimus.
Antipsychotics: Clozapine, haloperidol and bromperidol, olanzapine, quetiapine, risperidone, aripiprazole, paliperidone.
Antivirals: Protease inhibitors for HIV treatment (e.g. indinavir, ritonavir, saquinavir).
Anxiolytics: Alprazolam.
Bronchodilatators or anti-asthma drugs: Theophylline.
Contraceptives: Hormonal contraceptives (alternative contraceptive methods should be considered). Cardiovascular drugs: Calcium channel blockers (dihydropyridine group) e.g. felodipine, digoxin, simvastatin, atorvastatin, lovastatin, cerivastatin, ivabradine.
Corticosteroids: Corticosteroids (e.g. prednisolone, dexamethasone).
Drugs used in erectile dysfunction: Tadalafil.
Immunosuppressants: Ciclosporin, everolimus, tacrolimus, sirolimus.
Thyroid agents: Levothyroxine.
Other drug interactions: Products containing oestrogens and/or progesterones.
Combinations that require specific consideration: Concomitant use of carbamazepine and levetiracetam has been reported to increase carbamazepine-induced toxicity.
Concomitant use of carbamazepine and isoniazid has been reported to increase isoniazid-induced hepatotoxicity.
The combination of lithium and carbamazepine may cause enhanced neurotoxicity in spite of lithium plasma concentrations being within the therapeutic range. Combined use of carbamazepine with metoclopramide or major tranquilisers, e.g. haloperidol, thioridazine, may also result in an increase in neurological side-effects.
Concomitant medication with Carbamazepine and some diuretics (hydrochlorothiazide, furosemide) may lead to symptomatic hyponatraemia.
Carbamazepine may antagonise the effects of non-depolarising muscle relaxants (e.g. pancuronium). Their dosage should be raised and patients monitored closely for a more rapid recovery from neuromuscular blockade than expected.
Carbamazepine, like other psychoactive drugs, may reduce alcohol tolerance. It is therefore advisable for the patient to abstain from alcohol.
Interference with serological testing: Carbamazepine may result in false positive perphenazine concentrations in HPLC analysis due to interference.
Carbamazepine and the 10,11-epoxide metabolite may result in false positive tricyclic antidepressant concentration in fluorescence polarized immunoassay method.

Store at temperatures not exceeding 30°C.

Anticonvulsants / Drugs for Neuropathic Pain

N03AF01 - carbamazepine ; Belongs to the class of carboxamide derivatives antiepileptic.

Rx