Overview
Clarithromycin is a macrolide antibiotic used to treat various bacterial infections including respiratory tract infections, skin infections, and Helicobacter pylori-associated ulcers. It works by inhibiting bacterial protein synthesis and has activity against many Gram-positive and some Gram-negative organisms.
Mechanism of Action
Clarithromycin binds to the 50S ribosomal subunit of susceptible bacteria, inhibiting protein synthesis by blocking transpeptidation and translocation reactions. This bacteriostatic action prevents bacterial growth and replication.
Indications
- Treatment of respiratory tract infections including pharyngitis, tonsillitis, acute maxillary sinusitis, acute bacterial exacerbation of chronic bronchitis, and community-acquired pneumonia
- Skin and skin structure infections
- Helicobacter pylori eradication in combination with other agents
- Mycobacterium avium complex (MAC) infection prophylaxis and treatment in HIV patients
Common Doses
- 250 mg
- 500 mg
Dosage
Typical adult dosage is 250-500 mg twice daily for 7-14 days depending on infection type and severity. For H. pylori eradication, 500 mg twice daily is used in combination regimens. Dosage adjustments are required for renal impairment.
Contraindications
- Hypersensitivity to clarithromycin, erythromycin, or other macrolide antibiotics
- Concomitant use with cisapride, pimozide, astemizole, or terfenadine
- Concomitant use with ergotamine or dihydroergotamine
- History of cholestatic jaundice/hepatic dysfunction with prior clarithromycin use
- Concomitant use with lomitapide, lovastatin, or simvastatin in patients with renal or hepatic impairment
Side Effects
- Gastrointestinal disturbances (diarrhea, nausea, abdominal pain, dyspepsia)
- Headache, taste perversion
- Hepatotoxicity including elevated liver enzymes
- QT prolongation and cardiac arrhythmias
- Hypersensitivity reactions including anaphylaxis
- Clostridium difficile-associated diarrhea
- Oral candidiasis
Interactions
- Strong CYP3A inhibitor - increases concentrations of many drugs metabolized by this pathway
- Contraindicated with cisapride, pimozide, ergot alkaloids, certain statins, and colchicine in renal/hepatic impairment
- Use with caution with warfarin (increased anticoagulant effect), digoxin (increased levels), carbamazepine, theophylline, and many antiarrhythmics
- Reduces zidovudine absorption when taken simultaneously
Counseling Points
- Take with or without food, but take consistently with regard to meals
- Complete full course of therapy even if symptoms improve
- Report severe diarrhea, abdominal pain, or bloody stools immediately
- Avoid taking with antacids containing aluminum or magnesium within 2 hours
- Inform healthcare provider of all medications including OTC and herbal products
- Report any signs of allergic reaction or liver problems (jaundice, dark urine)