Possible Interaction: Nifedipine and Quinidine

“ Nifedipine area under the curve (AUC0–8) increased 36.6% from 333 to 455 μg · hr/L (P <.05) after quinidine administration.”

“These results suggest that quinidine inhibits nifedipine metabolism, and this pharmacokinetic interaction results in enhanced pharmacologic response.”

“Conflicting findings suggest that serum quinidine concentrations may be decreased or increased by nifedipine.”

“Conversely, quinidine increases plasma NF levels.”

“ Quinidine inhibited microsomal nifedipine oxidation and, in a series of human liver samples, rates of nifedipine oxidation were correlated with rates of quinidine oxidation.”

“…),quinidine (CAS 56-54-2) (approximately 5 micromol/l), mifepristone (CAS 84 371-65-3) (-8 micromol/l), 17alpha-ethinylestradiol (CAS 57-63-6) (approximately …/l), and cyclosporine A (CAS 59 865-13-3) (approximately 90 micromol/l) indicate that all these drugs have an inhibitory effect on nifedipine (….”

“The (45)Ca(2+) influx was saturated with [Ca(2+)](0) at 4 mmol/… and 30 degrees C. Divalent cations (10(-4)-10(-6)mol/L), nifedipine (10(-5)-10(-…)mol/L), and quinidine (10(-4)-10(-3)mol/L), inhibited the (…(-6)-10(-5)mol/L) stimulated it.”

“ Quinidine is a known inhibitor of cytochrome P450-mediated nifedipine metabolism.”

“ Quinidine pretreatment significantly inhibited the aromatization of nifedipine to its major first‐pass pyridine metabolite (M‐0) and prolonged the elimination half‐life of the calcium channel antagonist, both by about 40%.”

“Four case reports have been published that document a clinically significant drug interaction between nifedipine and quinidine in patients with left ventricular dysfunction.”

“Clinicians should be alert to the possibility of an alteration in quinidine serum concentrations when instituting or discontinuing nifedipine in patients receiving quinidine.”