Azithromycin: Macrolide Antibiotic Drug Profile

What is Azithromycin?

Azithromycin is a broad-spectrum macrolide antibiotic used to treat various bacterial infections throughout the body. It belongs to the macrolide class of antibiotics, which are known for their effectiveness against gram-positive bacteria and certain gram-negative organisms. This medication is commonly prescribed for respiratory tract infections, skin infections, and sexually transmitted diseases caused by susceptible bacteria.

Uses

Azithromycin is approved for treating several types of bacterial infections:

• Respiratory tract infections: Including pneumonia, bronchitis, and sinusitis caused by susceptible bacteria such as Streptococcus pneumoniae and Haemophilus influenzae
• Skin and soft tissue infections: Treatment of cellulitis, impetigo, and other bacterial skin infections
• Sexually transmitted infections: Single-dose treatment for chlamydia and gonorrhea, as well as treatment for pelvic inflammatory disease
• Ear infections: Acute otitis media in children and adults when caused by susceptible organisms
• Mycobacterial infections: Prevention and treatment of Mycobacterium avium complex in patients with HIV/AIDS

How it works

Azithromycin works by binding to the 50S ribosomal subunit of susceptible bacteria, which interferes with protein synthesis essential for bacterial growth and reproduction. This mechanism stops bacteria from multiplying and allows the body’s immune system to eliminate the infection. The drug is generally bacteriostatic, meaning it stops bacterial growth rather than directly killing the organisms.

Side effects

Common side effects include:

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• Nausea and vomiting
• Diarrhea or loose stools
• Abdominal pain or cramping
• Headache
• Dizziness
• Fatigue or weakness
• Loss of appetite
• Mild skin rash

Serious side effects requiring immediate medical attention:

• Severe allergic reactions (difficulty breathing, facial swelling, severe rash)
• Clostridioides difficile-associated diarrhea (severe, persistent, or bloody diarrhea)
• Irregular heartbeat or chest pain
• Severe liver problems (yellowing of skin or eyes, dark urine)
• Hearing loss or ringing in ears

Warnings and precautions

• Heart rhythm disorders: Patients with existing QT prolongation, low potassium or magnesium levels, or those taking medications that affect heart rhythm should use azithromycin with caution
• Liver disease: Individuals with severe liver impairment may require dose adjustments or alternative treatments, as the drug is primarily metabolized by the liver
• Pregnancy and breastfeeding: Classified as FDA pregnancy category B; generally considered safe during pregnancy when benefits outweigh risks, and passes into breast milk in small amounts
• Myasthenia gravis: May worsen muscle weakness in patients with this neurological condition
• Antibiotic resistance: Should only be used for confirmed or strongly suspected bacterial infections to prevent development of drug-resistant bacteria

Interactions

• Warfarin: May increase bleeding risk by enhancing anticoagulant effects
• Digoxin: Can increase digoxin blood levels, potentially leading to toxicity
• Antacids containing aluminum or magnesium: May reduce azithromycin absorption when taken simultaneously
• Ergot alkaloids: Risk of severe vasoconstriction and ergot toxicity
• QT-prolonging medications: Including certain antiarrhythmics, antipsychotics, and antidepressants may increase risk of dangerous heart rhythm changes
• Cyclosporine: May increase cyclosporine levels and risk of kidney toxicity
• Phenytoin: Potential for increased phenytoin levels and toxicity
• Terfenadine and cisapride: Contraindicated due to risk of serious cardiac arrhythmias

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Dosage

Adult dosages vary depending on the type and severity of infection being treated. For most respiratory infections, the typical regimen is 500mg on day one, followed by 250mg daily for days two through five. For sexually transmitted infections like chlamydia, a single 1000mg dose is often prescribed. For skin and soft tissue infections, doses may range from 250mg to 500mg daily for 3-5 days. Pediatric dosing is weight-based and typically calculated as 10mg/kg on day one, followed by 5mg/kg daily for four additional days. All dosing should be individualized and determined by a qualified healthcare provider based on the specific infection, patient factors, and local resistance patterns.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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