Drug reference

Azithromycin

Macrolide · Antibiotic

Also known as Azithromycin Dihydrate, Zithromax, Azithral, Azee, Zmax

START

500 mg PO once daily × 3 days OR 500 mg D1 then 250 mg D2-5

TYPICAL MAX

1,500 mg total course (CAP / typhoid)

STOP IF

QT prolongation · liver disease

WATCH

QTc · LFTs · hearing

CDSCO approvedSchedule HJan AushadhiATC J01FA10

Dose laddermg/d

Renal dose adjustmenteGFR mL/min/1.73m²

KDIGO 2024 + manufacturer label

Pharmacokineticsplasma · t hours

ONSET: 2h · tissue distribution
PEAK: 3h · Cmax plasma
t½: 2.8d · terminal t½ (tissue depot)
DURATION: 5d · post-dose tissue activity (5 days)

EXCRETION

Biliary unchanged · low CYP involvement

route + CYP

INTERACTIONS

12 major

incl. contraindicated

PREGNANCY

Category B — preferred macrolide in pregnancy

FDA category + note

Top interactionssee all 12 →

CisaprideContraindicatedDatabaseDDInter
PimozideContraindicatedDatabaseDDInter
AmiodaroneSevereDatabaseDDInter
AmisulprideSevereDatabaseDDInter

Available in India

4,455 branded formulations and 703 fixed-dose combinations. Look up specific brands in the Drugs workspace.

Jan Aushadhi — generic available at GoI pharmacies

Mechanism

Azithromycin, a macrolide antibiotic, inhibits bacterial protein synthesis by binding to the 50S ribosomal subunit of susceptible microorganisms. This binding prevents the translocation of peptides, thereby blocking the growth and replication of bacteria. Its prolonged tissue half-life allows for shorter treatment durations and once-daily dosing.

Indications

Community-acquired pneumonia (CAP)Acute bacterial exacerbation of chronic bronchitis (ABECB)Pharyngitis/Tonsillitis (Streptococcus pyogenes)Acute otitis mediaSkin and skin structure infectionsUrethritis and cervicitis (due to Chlamydia trachomatis)Genital ulcer disease (Chancroid)Mycobacterium avium complex (MAC) infection (prophylaxis and treatment)Travellers' diarrhea (off-label)Uncomplicated gonorrhoea (off-label, less preferred due to resistance)Traveler's diarrheamycobacterium avium complex infectiondisseminated mycobacterium avium complex prophylaxis in hivdisseminated mycobacterium avium complex treatmentMild-moderate babesiosis (in combination with atovaquone)Toxoplasmosis (alternative regimen, less effective)conjunctivitisblepharitissuperficial ocular infectionsProphylaxis against Mycobacterium avium complex (MAC) in HIV/AIDS patients with low CD4 countSurgical prophylaxis (for penicillin allergic patients)legionnaires’ pneumoniachlamydia trachomatis (nonspecific urethritis, genital infections, chlamydial pneumonia, trachoma)donovanosis (calymmatobacterium granulomatis)chancroidppng urethritispharyngitistonsillitissinusitisotitis mediapneumoniasacute exacerbations of chronic bronchitisstreptococcal skin and soft tissue infectionsstaphylococcal skin and soft tissue infectionsprophylaxis and treatment of MAC in AIDS patients (in combination with at least one other drug)multidrug resistant typhoid fever (in patients allergic to cephalosporins)toxoplasmosisTreatment of MAC infection in immunocompromized (HIV-AIDS) patientsProphylaxis of MAC infection in HIV-AIDS patientsM. fortuitum infectionM. kansasii infectionM. marinum infectionNongonococcal Urethritis (NGU)Mycoplasma genitalium infection (efficacy declining, especially if resistant)Lymphogranuloma Venereum (LGV) proctitis (alternative therapy)Shigellosis (second-line)Adjunctive antibiotic for patients with moderate or severe dehydration due to choleraChemoprophylaxis for leptospirosisReduced exacerbation frequency and longer time to first exacerbation in subjects with a history of exacerbation in the past 6 months, particularly effective in older patients, former smokers, and milder COPD

Dosing

Adult: For CAP, pharyngitis/tonsillitis, skin/skin structure infections: 500 mg orally once daily for 3 days, or 500 mg orally once on Day 1 followed by 250 mg once daily on Days 2-5. For urethritis/cervicitis (C. trachomatis) or genital ulcer disease (Chancroid): 1 g orally as a single dose.
Pediatric: For Acute Otitis Media: 30 mg/kg orally as a single dose, or 10 mg/kg once daily for 3 days, or 10 mg/kg once daily on Day 1 followed by 5 mg/kg once daily on Days 2-5. For Pharyngitis/Tonsillitis: 12 mg/kg orally once daily for 5 days.
Renal adjustment: No dosage adjustment is necessary for mild to moderate renal impairment (creatinine clearance > 10 mL/min). Data are insufficient for severe renal impairment (creatinine clearance < 10 mL/min), so caution is advised.
Hepatic adjustment: Use with caution in patients with mild to moderate hepatic impairment. Azithromycin is primarily excreted by the liver; therefore, avoid use in severe hepatic impairment due to risk of increased systemic exposure and hepatic dysfunction.
Geriatric: No specific dosage adjustment is recommended for elderly patients. However, caution should be exercised due to potential for QT prolongation and comorbidities, particularly cardiac issues.
Max dose: Typically 500 mg/day orally for multi-day regimens or 1g as a single dose for specific indications. Intravenous maximum doses depend on the indication (e.g., 500 mg IV once daily).

Pharmacokinetics

Onset

Rapid absorption after oral administration.

Peak effect

Oral: 2-3 hours.

Duration

Due to extensive tissue distribution and slow release from tissues, its effects persist for several days after the last dose, enabling short courses of therapy.

Half-life

Terminal elimination half-life is approximately 68-72 hours.

Bioavailability

Approximately 37% (oral suspension/tablet).

Protein binding

Variable, approximately 7% to 50% depending on plasma concentration.

Metabolism

Undergoes minor hepatic metabolism via demethylation; not extensively metabolized by CYP450 enzymes.

Excretion

Primarily excreted unchanged in the bile and feces (major route). A small percentage (<10%) is excreted via urine.

Contraindications

Hypersensitivity to azithromycin, erythromycin, any macrolide, or ketolide antibiotic
History of cholestatic jaundice/hepatic dysfunction associated with prior azithromycin use
Concurrent use with pimozide (due to QT prolongation risk)
Severe hepatic impairment
Prolonged QTc interval

Side effects

Common

NauseaVomitingDiarrheaAbdominal painHeadacheDizzinessFlatulenceRashGI toxicityOtotoxicityPseudomembranous colitismild gastric upsetHearing lossDevelopment of macrolide-resistant organisms

Serious

QT interval prolongation
Torsades de Pointes
Clostridium difficile-associated diarrhea (CDAD)
Hepatotoxicity (including cholestatic jaundice and hepatic failure)
Severe allergic reactions (e.g., angioedema, anaphylaxis)
Stevens-Johnson syndrome (SJS)
Toxic epidermal necrolysis (TEN)
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) syndrome
Exacerbation of myasthenia gravis
QT prolongation
Sudden death
Induction of resistant strains of bacteria
QTc interval prolongation (increased risk of death from cardiovascular causes, especially in patients with underlying heart disease)
Tinnitus and reversible deafness (especially in elderly)

Pregnancy & lactation

Pregnancy

Category B — preferred macrolide in pregnancy

Lactation

Azithromycin is excreted in human milk. While generally considered compatible, caution should be exercised. Monitor breastfed infants for gastrointestinal side effects (such as diarrhea, vomiting, or feeding intolerance) and candidiasis.