VitalsCentral

Azithromycin

Zithromax | Z-Pack | Azithrocin

FDA ApprovedAnti-InfectivesMacrolides
FDA: 1991Half-life: 68 hours (tissue)Pregnancy: Category B

Overview

Macrolide antibiotic effective against a broad range of bacterial infections including respiratory, skin, and sexually transmitted infections.

Indications

  • Community-acquired pneumonia
  • Acute bacterial sinusitis
  • Pharyngitis/tonsillitis
  • Skin infections
  • Chlamydia
  • Traveler's diarrhea
  • MAC prophylaxis (HIV)

Contraindications

  • History of cholestatic jaundice with azithromycin
  • Hypersensitivity to macrolides

Classification

Anti-InfectivesMacrolidesRespiratory SystemImmune System

Mechanism of Action

Binds to 50S ribosomal subunit, inhibiting bacterial protein synthesis. Bacteriostatic at therapeutic concentrations, bactericidal at high concentrations.

Pharmacodynamics

Concentration-dependent killing with prolonged post-antibiotic effect. Accumulates in phagocytes and is released slowly at infection sites.

Pharmacokinetics

Absorption
Rapidly absorbed. Bioavailability 37% (capsule). Food decreases absorption of capsules but not tablets.
Distribution
Extensive tissue distribution. Concentrations in tissues 10-100x higher than plasma.
Metabolism
Hepatic demethylation (minimal). Primarily excreted unchanged.
Excretion
Biliary excretion (major route). Renal (6% unchanged).
Half-life
68 hours (tissue)
Bioavailability
37% (capsule), 52% (suspension)
Protein Binding
7-51% (concentration-dependent)

Dosage

Typical dosage: 500mg day 1, then 250mg days 2-5 (Z-Pack). Or 500mg daily x 3 days.

Available Forms

  • Tablet
  • Z-Pack (dose pack)
  • Oral suspension
  • IV injection
  • Eye drops

Side Effects

Common

  • Diarrhea
  • Nausea
  • Abdominal pain
  • Vomiting

Serious

  • QT prolongation
  • Hepatotoxicity
  • C. difficile colitis
  • Myasthenia gravis exacerbation

Rare

  • Torsades de pointes
  • Acute interstitial nephritis
  • Stevens-Johnson syndrome

Drug Interactions

moderate

May enhance anticoagulant effect. Monitor INR closely during and after azithromycin treatment.

minor

Aluminum/magnesium antacids reduce absorption. Take azithromycin 1 hour before or 2 hours after antacids.

Warnings

Pregnancy

Category B

Toxicity

LD50 >2000 mg/kg (oral, rat)

Overdose

Symptoms: nausea, vomiting, diarrhea, reversible hearing loss. Treatment: supportive care.

References

Looking for patient-friendly information? Visit RemedyDoor for easy-to-read guides about this medication.