Erythromycin is a very widely used antibiotic and is a substrate and inhibitor of cytochrome P450 (CYP3A) enzymes.
Important interactions involving erythromycin/ other macrolides are listed in Appendix 1 of the British National Formulary. The following are not comprehensive lists.
- the following should not be co-administered with erythromycin: amisulpride, simvastatin, ergotamine, dihydroergotamine, tolterodine, cisapride, pimozide, terfenadine and mizolastine
- erythromycin may increase serum concentrations of CYP metabolised drugs including: atorvastatin, bromocryptine, carbamazepine, cilostazole, cyclosporin, clozapine, midazolam, phenytoin, quinidine, tacrolimus, rifabutin, theophylline*, valproate, alfentanil, zopiclone, warfarin and digoxin
- increased erythromycin levels may occur with other CYP3A inhibitors, such as ‘azole’ antifungals, some calcium channel blockers (diltiazem, verapamil), anti-HIV protease inhibitors (e.g. amprenavir, ritonavir, saquinavir)
*theophylline also decreases erythromycin levels
Notes:
- cytochrome P450 inhibition caused by macrolides may have a slow onset and persist for several days after cessation of treatment
- erythromycin can increase the ECG QT interval and may rarely be associated with arrhythmias, such as torsades de pointes
- risk is increased when erythromycin is co-administered with other drugs that increase QT interval and with type 1(a) and type III anti-dysrhythmics (e.g. disopyramide, quinidine, amiodarone)
- avoid co-administration of drugs which increase QT interval and have pharmacokinetic interactions with erythromycin (e.g. mizolastine, cisapride, terfenadine)
Reference:
- Current Problems in Pharmacovigilance 2006;31:1-12.