| Concomitant use of erythromycin with simvastatin, tolterodine, mizolastine, amisulpride, terfenadine or astemizole is likely to result in an enhanced risk of cardio toxicity with these drugs. The concomitant use of erythromycin with either simvastatin, tolterodine, mizolastine, amisulpride, astemizole or terfenadine is therefore contra-indicated.The metabolism of terfenadine and astemizole is significantly altered when either are taken concomitantly with erythromycin. Rare cases of serious cardio-vascular events have been observed, including torsades de pointes, other ventricular arrhythmias and cardiac arrest. Death has been reported with the terfenadine/erythromycin combination.Elevated cisapride levels have been reported in patients receiving erythromycin and cisapride concomitantly. This may result in QT prolongation and cardiac arrhythmias including ventricular tachycardia, ventricular fibrillation and torsades de pointes. Similar effects have been observed with concomitant administration of pimozide and clarithromycin, another macrolide antibiotic. Concurrent use of erythromycin and ergotamine or dihydroergotamine has been associated in some patients with acute ergot toxicity, characterised by the rapid development of severe peripheral vasospasm and dysaesthesia.Increases in serum concentrations of the following drugs metabolised by the cytochrome P450 system may occur when administered concurrently with erythromycin: alfentanil, astemizole, bromocriptine, carbamazepine, cyclosporin, digoxin, dihydroergotamine, disopyramide, ergotamine, hexobarbitone, midazolam, phenytoin, quinidine, tacrolimus, terfenadine, theophylline, triazolam, valproate, and warfarin. Appropriate monitoring should be undertaken and dosage should be adjusted as necessary.Erythromycin has been reported to decrease the clearance of zopiclone and thus may increase the pharmacodynamic effects of this drug.When oral erythromycin is given concurrently with theophylline, there is also a significant decrease in erythromycin serum concentrations. The decrease could result in subtherapeutic concentrations of erythromycin. | |