Azithromycin

Indication & Dosage

Oral

Skin and soft tissue infections

Adult: 500 mg once daily for 3 days. Alternatively, 500 mg as a single dose on the 1st day followed by 250 mg once daily for 4 days.

Child: >6 mth 10 mg/kg; 15-25 kg: 200 mg; 26-35 kg: 300 mg; 36-45 kg: 400 mg. All doses to be taken once daily for 3 days.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Respiratory tract infections

Adult: 500 mg once daily for 3 days. Alternatively, 500 mg as a single dose on the 1st day followed by 250 mg once daily for 4 days.

Child: >6 mth 10 mg/kg; 15-25 kg: 200 mg; 26-35 kg: 300 mg; 36-45 kg: 400 mg. All doses to be taken once daily for 3 days.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Uncomplicated genital infections due to Chlamydia trachomatis

Adult: 1 g as a single dose.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Non-gonococcal cervicitis/urethritis due to Chlamydia trachomatis

Adult: 1 g as a single dose.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Chancroid

Adult: 1 g as a single dose.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Uncomplicated gonorrhoea

Adult: 2 g as a single dose.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Prophylaxisof disseminated Mycobacterium avium complex (MAC) infections

Adult: 1.2 g once wkly. For treatment or secondary prophylaxis: 500 mg once daily w/ other antimycobacterials.

Child: 20 mg/kg once wkly. Max: 1.2 g. Alternatively 5 mg/kg once daily. Max: 250 mg.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Active immunisation against typhoid fever caused by Salmonella typhi

Adult: 1 g once daily for 5 days or 500 mg once daily for 7 days.

Child: 3-17 yr 20 mg/kg (Max: 1 g) once daily for 5-7 days or 10 mg/kg (Max: 500 mg).

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Oral

Granuloma inguinale

Adult: Initially, 1 g followed by 500 mg daily. Alternatively, 1 g once a wk for at least 3 wk, until all lesions have completely healed.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Suspension: Reconstitute w/ the recommended amount of water and shake well prior to consumption.

Intravenous

Community-acquired pneumonia

Adult: 500 mg as single IV daily dose for at least 2 days followed by a single oral daily dose of 500 mg to complete 7-10 days of therapy.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Initial solution: Using a standard 5 mL syringe add 4.8 mL sterile water for inj to a 500 mg vial and shake until all drugs dissolved. Further dilute the solution w/ 250 or 500 mL of a compatible IV solution to a concentration of 2 or 1 mg/mL.

Intravenous

Pelvic inflammatory disease

Adult: 500 mg as single IV daily dose for 1-2 days followed by a single oral daily dose of 250 mg tablet to complete a 7-day therapy.

Elderly: No dosage adjustment needed.

Renal impairment: No dosage adjustment needed.

Hepatic impairment: No dosage adjustment needed.

Reconstitution: Initial solution: Using a standard 5 mL syringe add 4.8 mL sterile water for inj to a 500 mg vial and shake until all drugs dissolved. Further dilute the solution w/ 250 or 500 mL of a compatible IV solution to a concentration of 2 or 1 mg/mL.

Ophthalmic

Bacterial conjunctivitis

Adult: Instill 1 drop in the affected eye(s) bid for 2 days, then once daily for the next 5 days.

Administration

Cap & extended release microspheres: Should be taken on an empty stomach. Take on an empty stomach 1 hr before or 2 hr after meals.

Tab & susp: May be taken with or without food. May be taken w/ meals to reduce GI discomfort.

Overdosage

Symptoms: Reversible loss of hearing, severe nausea, vomiting and diarrhoea. Management: Administer activated charcoal; symptomatic and supportive treatment.

Contraindications

Known hypersensitivity to azithromycin, erythromycin, any macrolide or ketolide antibiotic. Coadministration w/ pimozide. History of cholestatic jaundice/hepatic dysfunction associated w/ prior use of azithromycin.

Special Precautions

May increase the risk of torsades de pointes and fatal heart arrhythmias in patients w/ 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. Monitoring Parameters Liver function tests, CBC w/ differential.

Adverse Drug Reactions

GI disturbances, visual impairment and irritation; deafness, dizziness, headache, fatigue, anorexia, paraesthesia, dysgeusia, nasal congestion, sinusitis, facial swelling, periocular swelling, pruritus, rash, urticaria, arthralgia, vaginitis; inj site pain, inflammation; decreased lymphocyte count and blood bicarbonate, increased eosinophil count, transaminase levels and/or alkaline phosphatase levels.

Potentially Fatal: Angioedema and cholestatic jaundice.

Drug Interactions

Increases serum concentrations of digoxin, ciclosporin, terfenadine, hexobarbital and phenytoin. Decreased rate of absorption w/ antacids containing aluminium and magnesium. Increased risk of ergot toxicity.

Potentially Fatal: Increased risk of cardiotoxicity w/ pimozide.

Food Interaction

Food may alter absorption depending on the formulation.

Pregnancy Category (US FDA)

Category B: Either animal-reproduction studies have not demonstrated a foetal risk but there are no controlled studies in pregnant women or animal-reproduction studies have shown an adverse effect (other than a decrease in fertility) that was not confirmed in controlled studies in women in the 1st trimester (and there is no evidence of a risk in later trimesters).

Storage

Intravenous: Store below 30°C. Ophthalmic: Store below 30°C. Oral: Store below 30°C.

Mechanism of Action

Azithromycin is a semisynthetic azalide antibiotic. It blocks transpeptidation by binding to 50s ribosomal subunit of susceptible organisms and disrupting RNA-dependent protein synthesis at the chain elongation step.

Absorption: Rapidly absorbed from the GI tract. Reduced by food (capsule formulation). Absolute bioavailability: Approx 34-52%. Time to peak plasma concentration: Oral tab: 2-3 hr; IV: 1-2 hr.

Distribution: Extensive into the tissues (higher than those in blood), WBC (high concentrations), CSF (small amounts). Volume of distribution: 31-33 L/kg. Plasma protein binding (concentration dependent): 7-51% (oral and IV).

Metabolism: Hepatic metabolism via demethylation.

Excretion: Via bile (as unchanged drug and inactive metabolites); urine (approx 6% of oral dose). Terminal elimination half-life: About 68 hr.

CIMS Class

Macrolides

ATC Classification

J01FA10 - azithromycinBelongs to the class of macrolides. Used in the systemic treatment of infections.

S01AA26 - azithromycinBelongs to the class of antibiotics. Used in the treatment of eye infections.