Clarithromycin is a potent inhibitor of CYP3A4, and as such may cause toxicity with Theophylline, Simvastatin, and Ciclosporin
- Often preferred to Erythromycin as fewer GI effects
- However more expensive than Erythromycin
Action
- A macrolide that binds to the 50s subunit of the bacterial ribosome
Properties
- Penetrates most tissues except CSF and half-life is about 6 hours
- Its 14 lactone macrolide ring inhibits CYP 3A4
Indications
- Community acquired pneumonia
- Atypical pneumonias - Mycoplasma, chlamydia, legionella
- Alternative to Erythromycin
- Triple therapy for Helicobacter
Interactions
- Increased Theophylline, carbamazepine, Ciclosporin, colchicine, clozapine
- Administration of Clarithromycin with terfenadine is contraindicated
- Inducers of CYP3A enzymes reduce Clarithromycin
- Increased Sildenafil, Tadalafil, and Vardenafil toxicity
- Potential Warfarin toxicity, Increased protease inhibitors
Dose
- Mild infection: Clarithromycin 250-500 mg bd PO
- Moderate/Severe: Clarithromycin 500 mg bd IV Infusion into a large proximal vein
Cautions
- Known QT prolongation or with drugs that prolong QT
- Acute porphyria, liver disease, Reduce dose in renal failure
Contraindications
- Administration of Clarithromycin with terfenadine is contraindicated
Side effects
- Nausea, vomiting, dyspepsia less common than Erythromycin
- Diarrhoea, Skin rashes, Stevens-Johnson syndrome, Toxic epidermal necrolysis
- Cholestatic jaundice, pancreatitis, Prolonged QT interval
- Altered smell and taste. Hepatitis, Myalgia. Renal failure
References