Litcab Drug Interactions

Interactions which increase lithium concentrations: Serum lithium levels may be increased if one of the following drugs is co-administered. When appropriate, either lithium dosage should be adjusted or concomitant treatment stopped.
Metronidazole may reduce lithium renal clearance.
Non-steroidal anti-inflammatory drugs, including cyclo-oxygenase (COX) 2 inhibitors (monitor serum lithium concentrations more frequently if NSAID therapy is initiated or discontinued).
Angiotensin-converting enzyme (ACE) inhibitors.
Angiotensin II receptor antagonists.
Diuretics (thiazides show a paradoxical antidiuretics effect resulting in possible water retention and lithium intoxication). If a thiazide diuretic has to be prescribed for lithium-treated patient, lithium dosage should first be reduced and the patient re-stabilised with frequent monitoring. Similar precautions should be exercised on diuretic withdrawal. Loop diuretics seem less likely to increase lithium levels.
Other drugs affecting electrolyte balance, eg, steroids, may alter lithium excretion and should therefore be avoided.
Tetracyclines.
Interactions which decrease serum lithium concentrations: Serum lithium levels may be decreased due to an increase in lithium renal clearance in case of concomitant administration of one of the following drugs: Xanthines (theophylline, caffeine); Sodium bicarbonate containing products; Diuretics (osmotic and carbonic anhydrase inhibitors); Urea; Calcitonin.
Interactions causing neurotoxicity: Co-administration of the following drugs may increase the risk of neurotoxicity: Antipsychotics (particularly Haloperidol at higher dosages), Flupentixol, Diazepam, Thioridazine, Fluphenazine, Chlorpromazine and Clozapine may lead in rare cases to severe neurotoxicity with symptoms, such as confusion, disorientation, lethargy, tremor, extra-pyramidal symptoms, and myoclonus. Increased lithium levels were present in some of the reported cases. Co-administration of Antipsychotics and Lithium may increase risk of Neuroleptic Malignant Syndrome, which may be fatal. Discontinuation of both drugs is recommended at the first signs of neurotoxicity.
Methyldopa.
Triptan derivatives and/or serotonergic Antidepressants such as Selective Serotonin Re-uptake Inhibitors (eg, Fluvoxamine and Fluoxetine) as this combination may precipitate a serotoninergic syndrome, which justifies immediate discontinuation of treatment.
Calcium channel blockers may lead to neurotoxicity with symptoms such as ataxia, confusion and somnolence. Lithium concentrations may be increased.
Carbamazepine may lead to dizziness, somnolence, confusion and cerebellar symptoms such as ataxia.
Other: Caution is advised if lithium is co-administered with other drugs that prolong the QT interval, eg, Class IA (eg, Quinidine, Disopyramide), or Class III (eg, Amiodarone) Antiarrhythmic agents, Cisapride, Antibiotics such as Erythromycin, Antipsychotics such as Thioridazine or Amisulpride. Caution is advised if lithium is co-administered with drugs that lower the epileptic threshold, eg, Antidepressants such as SSRIs, Tricyclic antidepressants, Antipsychotic, Anaesthetics, Theophylline.
Lithium may prolong the effects of neuromuscular blocking agents. There have been reports of interaction between lithium and phenytoin, indomethacin and other prostaglandin-synthetase inhibitors.
Serotonin Syndrome: Serotonin syndrome is a potentially life-threatening adverse reaction, with is caused by an excess of serotonin (eg, from overdose or concomitant use of serotonergic drugs), necessitating hospitalisation and even causing death. Symptoms may include: Mental status changes (agitation, confusion, hypomania, eventually coma); Neuromuscular abnormalities (myoclonus, tremor, hyperreflexia, rigidity, akathisia); Autonomic hyperactivity (hypo or hypertonia, tachycardia, shivering, hyperthermia, diaphoresis; Gastrointestinal symptoms (diarrhoea).
Strict adherence to the recommended doses is an essential factor for the prevention of the occurrence of this syndrome.