Azithromycin
ZITHROMAX
Pronunciation: az-ith-roe-MYE-sin
“Zippered mice in there, Pak’d to the max”
QT prolongation
Z-PAK is 5-day course, 6 tabs total
What it isMacrolide that inhibits the 50S ribosomal subunit; respiratory and atypical bacterial infections.
Why this oneConcentrates in tissue and needs less frequent dosing than most antibiotics, with far fewer CYP3A4 interactions than clarithromycin.
What limits itQT prolongation and widespread pneumococcal resistance limit empiric use; it is not a substitute for beta-lactam coverage.
Pearls
- Chronic off-label use cuts exacerbations in COPD and severe asthma.
- Long-term courses risk reversible hearing loss and resistance.
- Option in severe beta-lactam allergy.
Azithromycin prescription history
Animated chart of estimated U.S. prescriptions per year, Antibacterials (systemic) (1938–2026). Azithromycin enters in 1992 (estimated).
FDA-approved for
- bacterial infections (1991)
Principal riskQT prolongation
Classes and tags
Clinical profile
Legacy pregnancy categoryB
Defining liabilityQT prolongation and rare serious hepatic or allergic reactions.
FDA label
Read the full label on DailyMed ↗
NO BOXED WARNINGS
| FDA dosing | Population | Start | Target | Max |
|---|---|---|---|---|
| CAP, pharyngitis/tonsillitis (2nd-line), uncomplicated skin/skin-structure | Adult | 500 mg x1 (Day 1) | 250 mg QD Days 2-5 | 1.5 g/course |
| Acute bacterial exacerbation of COPD/bronchitis | Adult | 500 mg QD x3 days OR 500 mg x1 Day 1 | 250 mg QD Days 2-5 (5-day option) | 1.5 g/course |
| Acute bacterial sinusitis | Adult | 500 mg QD x3 days | 500 mg QD x3 days | 1.5 g/course |
| Chancroid, non-gonococcal urethritis/cervicitis | Adult | 1 g single dose | 1 g x1 | 1 g |
| Gonococcal urethritis/cervicitis | Adult | 2 g single dose | 2 g x1 | 2 g |
| Acute otitis media | Peds ≥6 mo | 30 mg/kg x1 OR 10 mg/kg QD x3 days OR 10 mg/kg Day 1 then 5 mg/kg QD Days 2-5 | per chosen regimen | 1500 mg/course |
| Acute bacterial sinusitis | Peds ≥6 mo | 10 mg/kg QD x3 days | 10 mg/kg QD x3 days | 1500 mg/course |
| Community-acquired pneumonia | Peds ≥6 mo | 10 mg/kg x1 Day 1 | 5 mg/kg QD Days 2-5 | 1500 mg/course |
| Pharyngitis/tonsillitis | Peds ≥2 y | 12 mg/kg QD x5 days | 12 mg/kg QD x5 days | 500 mg/day |
Renal Undefined
Hepatic Undefined
Instructions
- Take with or without food
- For STIs, perform baseline syphilis and gonorrhea testing (not reliable for syphilis)
Available strengths
- tab 250, 500, 600 mg
- susp 100, 200 mg/5 mL
- inj 500 mg
- drops 1 %
Contraindications
- History of cholestatic jaundice/hepatic dysfunction with prior azithromycin use
Cautions
- Serious allergic/skin reactions (anaphylaxis, angioedema, SJS/TEN, DRESS, AGEP) — discontinue
- Hepatotoxicity (can be fatal) — discontinue if hepatitis signs occur
- QT prolongation and torsades de pointes; caution with QT-risk patients/drugs
- Infantile hypertrophic pyloric stenosis in neonates
- C. difficile-associated diarrhea; may exacerbate myasthenia gravis
Adverse reactions
- Diarrhea (5-14%)
- Nausea (3-18%)
- Abdominal pain (3-7%)
- Vomiting (2-7%)
Pregnancy Available data have not identified a drug-associated risk of birth defects or miscarriage
Lactation Present in human milk; monitor breastfed infant for diarrhea, vomiting, or rash
Cost
Generic entry2005
Open Azithromycin in the interactive console ↗
Memory aids: interaction avatars
Open Azithromycin in the interactive console ↗
Self-check
- How does azithromycin’s CYP3A4 interaction burden compare with clarithromycin?
Far fewer interactions. - Which cardiac effect limits azithromycin use?
QT prolongation.