Pharmaniaga Clarithromycin Drug Interactions

Theophylline: Clarithromycin use in patients who are receiving theophylline may be associated with an increase of serum theophylline concentrations. Monitoring of serum theophylline concentrations should be considered for patients receiving high doses of theophylline or with baseline concentrations in the upper therapeutic range.
Carbamazepine: Concomitant administration of single doses of clarithromycin and carbamazepine has been shown to result in increased plasma concentrations of carbamazepine. Blood level monitoring of carbamazepine may be considered.
Terfenadine: When clarithromycin and terfenadine were co-administered, plasma concentrations of the active acid metabolite of terfenadine were threefold higher, on average, than the values observed when terfenadine was administered alone. The pharmacokinetics of clarithromycin and the 14-hydroxy-clarithromycin were not significantly affected by co-administration of terfenadine once clarithromycin reached steady-state conditions. Concomitant administration of clarithromycin with terfenadine is contraindicated.
Omeprazole: Clarithromycin 500 mg every 8 hours was given in combination with omeprazole 40 mg daily to healthy adult subjects. The steady-state plasma concentrations of omeprazole were increased by the concomitant administration of clarithromycin.
Zidovudine: Simultaneous oral administration of clarithromycin tablets and zidovudine to HIV-infected adult patients resulted in decreased steady-state zidovudine concentrations.
Oral anticoagulants: Concomitant administration of clarithromycin and oral anticoagulants may potentiate the effects of the oral anticoagulants. Prothrombin times should be carefully monitored while patients are receiving clarithromycin and oral anticoagulants simultaneously.
Elevated digoxin serum concentrations in patients receiving clarithromycin and digoxin concomitantly have also been reported. Some patients have shown clinical signs consistent with digoxin toxicity, including potentially fatal arrhythmias. Serum digoxin levels should be carefully monitored while patients are receiving digoxin and clarithromycin simultaneously.
The following drugs or drug classes are known or suspected to be metabolized by the same CYP3A isozyme: alprazolam, astemizole, carbamazepine, cisapride, cyclosporine, disopyramide, ergot alkaloids, lovastatin, methylprednisolone, midazolam, omeprazole, oral anticoagulants (eg, warfarin), pimozide, quinidine, rifabutin, simvastatin, tacrolimus, terfenadine and triazolam.
Co-administration of clarithromycin, known to inhibit CYP3A4, and a drug primarily metabolized by CYP3A4 may be associated with elevations in drug concentrations that could increase or prolong both therapeutic and adverse effects of the concomitant drug.
The following drugs or drug classes are known to be known or suspected to be metabolized by CYP3A isozyme: Domperidone.
Use of clarithromycin in patients concurrently taking drugs metabolized by the cytochrome P450 system (eg, Warfarin, ergot alkaloids, midazolam, lovastatin, phenytoin, ciclosporin) may be associated with an increase in the serum levels of these drugs.
Quinidine/disopyramide have been reported to cause torsade de pointes when taken in combination with clarithromycin.