PHARMACOLOGY

Pharmacotherapeutic Group: Macrolide antibiotic

 Pharmacodynamic properties: AZT (Azithromycin) is an azalide, a sub-class of the macrolide antibiotics. By binding to the 50S ribosomal subunit, AZT inhibits 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 resulting in inhibition of bacterial growth.

 Pharmacodynamic properties: AZT (Azithromycin) is a semi synthetic macrolide antibiotic of azalide class. AZT inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit of the bacterial ribosome. This binding inhibits peptidyl transferase activity and interferes with amino acid translocation during the process of translation this resulting in inhibition of bacterial growth.

Pharmacokinetic properties:

Absorption: Rapidly absorbed from the GI tract; Absolute bioavailability: Approx 34-52%; Time to peak plasma concentration: 2-3 hr

Distribution: Extensive into the tissues (higher than those in blood), WBC (high concentrations), CSF (small amounts); Plasma protein binding (concentration dependent)

Metabolism: Hepatic metabolism via demethylation (microbiologically inactive)

Excretion: Via bile (as unchanged drug and inactive metabolites); urine (approx 6% of oral dose); Terminal elimination half-life: 2-4days

 INDICATIONS

Acute bacterial sinusitis; Otitis media; Acute exacerbation of chronic bronchitis; Tonsillitis/Pharyngitis; Community acquired pneumonia; Skin and soft tissue infection; Acne; Sexually transmitted disease.

 DOSE

The dose of AZT is 1500mg to be administered as 500mg once daily for 3 consecutive days. Alternatively 500mg as a single dose on the 1^st day followed by 250mg once daily for 4 days may be given.

Uncomplicated chlamydia trachomatis urethritis and cervicitis: The dosage is 1000mg as a single oral dose.

Children under 45kg: 10mg/kg given as single dose for 3 days.

 CONTRAINDICATIONS

Known hypersensitivity to azithromycin, erythromycin, any macrolide or ketolide antibiotic; Co-administration with pimozide; History of cholestatic jaundice/hepatic dysfunction associated with prior use of azithromycin; Severe liver disease.

 SPECIAL PRECAUTIONS

May increase the risk of torsades de pointes and fatal heart arrhythmias in patients with prolonged QT interval, low K or Mg blood levels, slow heart rate and medication treating abnormal heart rhythms; Impaired hepatic and renal function; Pregnancy and lactation.

 ADVERSE DRUG REACTIONS

GI disturbances, visual impairment, irritation, deafness, dizziness, headache, fatigue, anorexia, paraesthesia, dysgeusia, nasal congestion, sinusitis, facial swelling, periocular swelling, pruritus, rash, urticaria, arthralgia, vaginitis. Potentially Fatal: Angioedema and cholestatic jaundice.

 DRUG INTERACTIONS

Increases serum concentrations of digoxin, ciclosporin, terfenadine, hexobarbital and phenytoin; Decreased rate of absorption with antacids containing aluminium and magnesium; Increased risk of ergot toxicity. Potentially Fatal: Increased risk of cardiotoxicity with pimozide.

PRESENTATION:

AZT 100 SUSPENSION: Each bottle contains 15ml of suspension.

AZT 200 SUSPENSION: Each bottle contains 15ml of suspension.

AZT 250: Each box contains 10 strip packs of 6 tablets per strip.

AZT 500: Each box contains 10 strip packs of 3 tablets per strip.