India · Typhoid Fever · Community Pneumonia · Paediatric mg/kg · Azee · Azithral · Zithromax
| Indication | Adult dose | Paediatric dose | Duration | Guideline |
|---|---|---|---|---|
| Typhoid — uncomplicated | 1g/day (2×500mg) × 7 days or 500mg × 7 days | 20 mg/kg/day × 7 days (max 1g) | 7 days | WHO 2018, NVBDCP India |
| CAP — mild/moderate | 500mg day 1, then 250mg × 4 days | 10 mg/kg/day (max 500mg) × 3–5 days | 3–5 days | BTS · IDSA |
| URTI / atypical / Mycoplasma | 500mg once daily | 10 mg/kg/day | 3–5 days | BNF |
| Pharyngitis / tonsillitis | 500mg once daily | 12 mg/kg/day (max 500mg) | 5 days | BNF · AAP |
| Chlamydia / STI | 1g single dose | Not routinely used | Single dose | WHO STI guidelines |
| Skin & soft tissue | 500mg once daily | 10 mg/kg/day | 3–7 days | BNF |
| MAC prophylaxis (HIV) | 1.2g weekly | 20 mg/kg weekly | Ongoing | NACO India guidelines |
Typhoid fever, caused by Salmonella enterica serotype Typhi, remains one of the most significant infectious diseases in India, with an estimated 4.5 million cases annually. The management of typhoid has changed substantially over the past decade due to the emergence of fluoroquinolone-resistant (FQR) and, more recently, extensively drug-resistant (XDR) Salmonella typhi strains across the Indian subcontinent.
Until the late 1990s, fluoroquinolones (ciprofloxacin, ofloxacin) were the standard of care for typhoid in India. Widespread resistance — now affecting over 95% of S. typhi isolates in some regions — has rendered fluoroquinolones clinically ineffective even when reported as sensitive on disc diffusion, due to the MIC creep phenomenon. The WHO, NVBDCP (National Vector Borne Disease Control Programme), and Indian Association of Paediatricians (IAP) all now recommend azithromycin as the first-line treatment for uncomplicated typhoid fever.
For adults with uncomplicated typhoid: 500 mg to 1g orally once daily for 7 days. Some Indian centres use 1g/day (two 500mg tablets) as a higher starting dose given the tissue pharmacokinetics of azithromycin. For children: 20 mg/kg/day as a single daily dose for 7 days, to a maximum of 1g per day. This is higher than the standard 10 mg/kg/day used for other indications. The 200mg/5ml suspension (Azee DT, Azithral) is well-suited for children who cannot swallow tablets.
Clinical response to azithromycin for typhoid typically occurs within 4–5 days, but the full 7-day course must be completed. Fever may persist for 3–5 days into treatment — this is not an indication to switch antibiotics unless the patient deteriorates clinically or develops complications (intestinal perforation, encephalopathy, myocarditis).
Community-acquired pneumonia in India has a mixed aetiology — Streptococcus pneumoniae and H. influenzae are the most common typical bacterial causes, while Mycoplasma pneumoniae, Chlamydophila pneumoniae, and Legionella are important atypical pathogens, particularly in young adults and those presenting without leukocytosis. Azithromycin's excellent activity against atypical pathogens and its once-daily, short-course regimen make it a preferred choice for mild-to-moderate CAP managed in the outpatient setting.
For moderate-to-severe CAP requiring hospitalisation, most Indian and international guidelines (BTS, IDSA/ATS) recommend combination therapy — a beta-lactam (amoxicillin or amoxicillin-clavulanate) plus azithromycin — to cover both typical and atypical organisms. Azithromycin monotherapy is appropriate for mild, outpatient CAP in otherwise healthy adults without comorbidities. Use CURB-65 (available on RxMedCalc) to risk-stratify CAP before deciding on monotherapy vs combination vs hospitalisation.
Azithromycin is an azalide — a subclass of macrolide — with a uniquely long tissue half-life of approximately 68 hours. It concentrates extensively in macrophages, neutrophils, and tissue sites (lung, tonsils, liver), achieving tissue concentrations 10–100 times the serum concentration. This tissue reservoir effect means that once-daily oral dosing maintains effective intracellular concentrations throughout the dosing interval. The drug continues to exert antimicrobial activity for several days after the last dose — which is why a 3-day Z-pack achieves 5 days of effective drug exposure.
Azithromycin carries a risk of QTc prolongation, particularly in patients with pre-existing cardiac disease, electrolyte abnormalities (hypokalaemia, hypomagnesaemia), or those co-prescribed other QT-prolonging drugs (fluoroquinolones, ondansetron, haloperidol, some antifungals). In elderly patients with cardiac risk factors or in hospitalised patients on multiple drugs, a baseline ECG is advisable before initiating azithromycin. This risk is generally low in otherwise healthy young patients receiving short courses.
Unlike most antibiotics, azithromycin does not require dose adjustment for renal impairment — it is excreted primarily via biliary-faecal routes with less than 6% renal excretion. This makes it particularly convenient in patients with CKD. However, caution is required in severe hepatic impairment (Child-Pugh C), as azithromycin undergoes hepatic metabolism and biliary excretion. Use with caution or avoid in decompensated liver disease.