Thromaxin

Tablet: A white bi-convex, oblong shaped film coated tablet, both sides being plain.
Each Film-Coated Tablet contains: Azithromycin (as dihydrate) USP 500 mg.
Suspension: White free flowing powder with a characteristic pleasant odor.
When reconstituted, each 5 mL suspension contains: Azithromycin (dihydrate) USP 200 mg.

Antibacterial (Macrolide).
Pharmacology: Pharmacodynamics: Azithromycin is an azalide, a sub-class of the macrolide antibiotics. By binding to the 50S-ribosomal sub-unit, azithromycin avoids the translocation of peptide chains from one side of the ribosome to the other. As a consequence of this, RNA-dependent protein synthesis in sensitive organisms is prevented.
PK/PD relationship: For azithromycin the AUC/MIC is the major PK/PD parameter correlating best with the efficacy of azithromycin. Following the assessment of studies conducted in children, the use of azithromycin is not recommended for the treatment of malaria, neither as monotherapy nor combined with chloroquine or artemisinin-based drugs, as non-inferiority to anti-malarial drugs recommended in the treatment of uncomplicated malaria was not established.
Mechanism of resistance: Resistance to azithromycin may be inherent or acquired. There are three main mechanisms of resistance in bacteria: target site alteration, alteration in antibiotic transport and modification of the antibiotic. Complete cross resistance exists among Streptococcus pneumoniae, beta-hemolytic streptococcus of group A, Enterococcus faecalis and Staphylococcus aureus, including methicillin resistant S. aureus (MRSA) to erythromycin, azithromycin, other macrolides and lincosamides.
Pharmacokinetics: Absorption: After oral administration the bioavailability of azithromycin is approximately 37%. Peak plasma levels are reached after 2-3 hours (C_max after a single dose of 500 mg orally was approximately 0.4 mg/L).
Distribution: Kinetic studies have shown markedly higher azithromycin levels in tissue than in plasma (up to 50 times the maximum observed concentration in plasma) indicating that the active substance is heavily tissue bound (steady state distribution volume of approximately 31 L/kg). Concentrations in target tissues such as lung, tonsil, and prostate exceed the MIC₉₀ for likely pathogens after a single dose of 500 mg. In experimental in vitro and in vivo studies azithromycin accumulates in the phagocytes, freeing is stimulated by active phagocytosis. In animal studies this process appeared to contribute to the accumulation of azithromycin in the tissue. In serum the protein binding of azithromycin is variable and depending on the serum concentration varies from 50% in 0.05 mg/L to 12% in 0.5 mg/L.
Excretion: Plasma terminal elimination half-life closely reflects the tissue depletion half-life of 2 to 4 days. About 12% of an intravenously administered dose is excreted in the urine unchanged over a period of 3 days; the majority in the first 24 hours. Biliary excretion of azithromycin, predominantly in unchanged form, is a major route of elimination. The identified metabolites (formed by N- and O-demethylating, by hydroxylating of the desosamine and aglycone rings, and by the splitting of the cladinose conjugate) are microbiologically inactive. After a 5 day treatment slightly higher (29%) AUC values were seen in the elderly volunteers (>65 years of age) compared to the younger volunteers (<45 years of age). However, these differences are not regarded as clinically relevant; therefore, a dose adjustment is not recommended.

Azithromycin is indicated in upper respiratory tract infections, including pharyngitis, tonsillitis, sinusitis, otitis media; lower respiratory tract infections including bronchitis, pneumonia; skin and soft tissue infections.
Azithromycin is also indicated in the treatment of uncomplicated genital infections due to Chlamydia trachomatis and uncomplicated gonorrhea from sexually transmitted diseases of men and women.
Azithromycin may also be used for prophylaxis in at-risk patients unable to take penicillin.

Adults: Upper respiratory tract infections, including sinusitis, pharyngitis, tonsillitis, otitis media, and lower respiratory tract infections including bronchitis, pneumonia, skin and soft tissue infections: The usual adult dose is 500 mg of Azithromycin (as dihydrate) once daily for 3 days. 1 dose/tablet before meals or 2 hours after meals.
An alternative to this dosage schedule is taking 2 capsules of Azithromycin 250 mg given as a single dose for the first day, followed by 1 capsule of Azithromycin 250 mg daily in the next 4 days.
Sexually transmitted diseases caused by Chlamydia trachomatis: The prescribed dosage is 1000 mg of Azithromycin (as dihydrate).
4 capsules of Azithromycin 250 mg or 2 tablets of Azithromycin 500 mg given as a single dose.
The single dose of 2 g may be given for uncomplicated gonorrhea (4 tablets of Azithromycin 500 mg tablets).
Children: Children over 6 months to 3 years (Up to 15 kg): The dose is 10 mg/kg as a single daily dose for 3 days. Measure the dose closely using the provided measuring dropper. The dropper is graduated in 0.25 mL, which will contain 10 mg of Azithromycin.
For children more than 3 years or weighing more than 15 kg, Azithromycin suspension should be administered using a spoon or measuring cup according to the following guidance: 3-7 years (15-25 kg): 1 measuring spoonful (5 mL) once daily for 3 days.
8-11 years (26-35 kg): 1 ½ measuring spoonfuls (7.5 mL) once daily for 3 days.
12-14 years (36-45 kg): 2 measuring spoonfuls (10 mL) once daily for 3 days.
Over 14 years (Over 45 kg): The dose is as for adults.
Or as directed by the physician.

Adverse events experienced in higher than recommended doses were similar to those seen at normal doses.
Symptoms: The typical symptoms of an overdose with macrolide antibiotics include reversible loss of hearing, severe nausea, vomiting and diarrhoea.
Treatment: In the event of overdose the administration of medicinal charcoal and general symptomatic treatment and supportive measures are indicated as required.

Azithromycin is contraindicated in patients with known hypersensitivity to Azithromycin and with hepatic disease.

Azithromycin absorption is reduced by 50% in the presence of food in the stomach. It should therefore be taken 1 hour before or 2 hours after meals. Macrolides have been known to increase the plasma concentration of digoxin and cyclosporin. Therefore, if co-administration is necessary caution should be exercised and serum level of digoxin and cyclosporin should be checked. Precaution should be taken in patients with hepatic and severe renal impairment. No adverse effects on the fetus during pregnancy is reported. However, caution should be exercised as with other drugs.

Pregnancy: There are no adequate and well-controlled studies on the use of azithromycin in pregnant women. In reproduction toxicity studies in animals, azithromycin was shown to pass the placenta, but no teratogenic effects were observed. The safety of azithromycin has not been confirmed with regard to the use of the active substance during pregnancy. Therefore, azithromycin should only be used during pregnancy if the benefit outweighs the risk.
Breast-feeding: Azithromycin is excreted in breast milk. Because of the long half-life, accumulation in the milk is possible. Information available from published literature indicates that, in short-term use, this does not lead to clinically relevant quantities in the milk. No serious side effects have been observed by azithromycin in breast-fed children. A decision should be taken whether breastfeeding is discontinued or that treatment with azithromycin is discontinued/initiated or not, taking into account the benefit of breastfeeding for the child and the benefit of treatment for the woman.

Azithromycin is well tolerated with a low incidence of adverse effects which are mild to moderate in nature and of gastro-intestinal in origin (e.g. nausea, abdominal discomfort, vomiting, flatulence and diarrhea). Allergic reactions, such as rash may occur in hypersensitive patients.

Azithromycin absorption is reduced in the presence of antacid. So, Azithromycin should be administered 1 hour before or 2 hours after taking an antacid.

Direction for reconstitution of suspension: Shake the bottle to loosen powder.
15 mL: Add 8 mL distilled water into the bottle and shake well until all the powder is dispersed.
Measure distilled water with the provided dropper, plastic measuring spoon or plastic graduated cylinder.
The reconstituted suspension should be used within 3 days of preparation and kept at temperatures not exceeding 30°C.
Shake the bottle well before each use.

Store at temperatures not exceeding 30°C. Protect from light.

Macrolides

J01FA10 - azithromycin ; Belongs to the class of macrolides. Used in the systemic treatment of infections.

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