Erythromycin potentiates PR interval prolonging effect of verapamil in the rat: A pharmacodynamic drug interaction
- Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, T6H 2N8 (Canada)
Calcium channel blockers and macrolide antibiotics account for many drug interactions. Anecdotal reports suggest interactions between the two resulting in severe side effects. We studied the interaction between verapamil and erythromycin in the rat to see whether it occurs at the pharmacokinetics or pharmacodynamic level. Adult male Sprague-Dawley rats received doses of 1 mg/kg verapamil or 100 mg/kg erythromycin alone or in combination (n = 6/group). Serial blood samples (0-6 h) were taken for determination of the drug concentrations using HPLC. Electrocardiograms were recorded (0-6 h) through subcutaneously inserted lead II. Binding of the drugs to plasma proteins was studied using spiked plasma. Verapamil prolonged PR but not QT interval. Erythromycin prolonged QT but not PR interval. The combination resulted in a significant increase in PR interval prolongation and AV node blocks but did not further prolong QT interval. Pharmacokinetics and protein binding of neither drug were altered by the other. Our rat data confirm the anecdotal human case reports that combination of erythromycin and verapamil can result in potentiation of the cardiovascular response. The interaction appears to be at the pharmacodynamic rather than pharmacokinetic level hence may be extrapolated to other calcium channel antagonists.
- OSTI ID:
- 20850354
- Journal Information:
- Toxicology and Applied Pharmacology, Journal Name: Toxicology and Applied Pharmacology Journal Issue: 1 Vol. 214; ISSN TXAPA9; ISSN 0041-008X
- Country of Publication:
- United States
- Language:
- English
Similar Records
Electrocardiographic Biomarkers for Detection of Drug-Induced Late Sodium Current Block
Structure and Function of the Macrolide Biosensor Protein, MphR(A), with and without Erythromycin