erythromycin, E-Mycin, Eryc, Ery-Tab, Pce, Pediazole, Ilosone (cont.)

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DRUG INTERACTIONS: Erythromycin when used with antiarrhythmic drugs such as, amiodarone (Cordarone), bretylium (Bretylol), disopyramide (Norpace), dofetilide (Tikosyn), procainamide (Pronestyl), quinidine (Quinaglute, Quinidex, Quinora) and sotalol (Betapace) exaggerates the effect of the antiarrhythmic drugs which may give rise to abnormal heart rhythms such as torsades de pointes.

Theophyllines such as theophylline (Theo-Dur), oxtriphylline (Choledyl SA), and aminophylline (Phyllocontin) reduce erythromycin blood levels by increasing elimination of erythromycin by the kidneys, which may reduce the effectiveness of erythromycin. Conversely, erythromycin inhibits the metabolism (breakdown) of theophyllines by the liver and causes an increase in blood levels of theophylline. High theophylline levels may give rise to side effects such as seizures and disturbances in heart rhythm. Therefore, the dose of theophyllines should be reduced or theophylline levels in the blood should be measured in patients taking erythromycin.

Erythromycin prevents digoxin (Lanoxin) from being eliminated by the kidneys; this in turn causes increased levels of digoxin in the blood. Increased levels of digoxin can cause disturbances in heart rhythm. Therefore, it is important to monitor and adjust digoxin doses when treating with erythromycin.

Erythromycin prevents the elimination of warfarin (Coumadin) from the body which can raise the levels of warfarin in the blood. Warfarin is an anticoagulant or blood thinner, and an increase in its level in blood can increase the risk of bleeding. It is important to monitor the effects of warfarin and adjust warfarin doses when treating with erythromycin.

Erythromycin inhibits the breakdown of HMG-CoA reductase inhibitors (statins) such as atorvastatin (Lipitor), lovastatin (Mevacor) and simvastatin (Zocor) by the liver leading to increased levels of statins in the blood. High levels of statins could result in severe myopathy (muscle damage) with rhabdomyolysis (rapid breakdown of skeletal muscle) that may damage the kidneys or even lead to death. Erythromycin also can elevate blood levels of some anti-seizure drugs such as carbamazepine (Tegretol) by preventing the breakdown of the anti-seizure drug by the liver. Therefore, doses of the anti-seizure drugs may need to be reduced during treatment with erythromycin.

Due to potential serious and even fatal heart problems, erythromycin should not be taken with terfenadine (Seldane), astemizole (Hismanal), pimozide (Orap), or cisapride (Propulsid).

Grapefruit juice may prevent the breakdown of erythromycin, resulting in elevated levels of erythromycin in the blood. Therefore, it is important to avoid eating grapefruit or drinking grapefruit juice during treatment with erythromycin.

PREGNANCY: Erythromycin crosses the placenta, but its level in the blood of the fetus is low. There are no adequate studies in pregnant women, hence pregnant women should only use erythromycin if it is felt that the benefits of treatment outweigh the potential but unknown risks.

NURSING MOTHERS: Erythromycin is excreted in breast milk; however, erythromycin is considered by the American Academy of Pediatrics to be compatible with breast-feeding. Caution should be exercised, however, when erythromycin is prescribed to women who are breast-feeding.

SIDE EFFECTS: The most frequent side effects of erythromycin are nausea, vomiting, loss of appetite, diarrhea, and abdominal pain. These gastrointestinal side effects are usually dose-related, i.e., more pronounced with higher doses. Allergic reactions such as hives, rash, or anaphylaxis (a severe allergic reaction which can lead to shock and death) have been reported rarely. Abnormal liver tests and liver damage also may occur with erythromycin.

Reference: FDA Prescribing Information


Last Editorial Review: 2/5/2009



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