Abstract
Objective: To investigate the influence of oral contraceptives on cytochrome P450 3A4 (P450NF) activity.
Methods: In 23 healthy women, the pharmacokinetics of nifedipine and its main metabolite dehydronifedipine in plasma were assessed after a single oral dose, prior to and after intake of one of two oral contraceptive formulations, one containing 2 mg dienogest and 0.03 mg ethinylestradiol (group A) and the other containing 0.125 mg levonorgestrel and 0.03 mg ethinylestradiol (group B).
Results: While the intake of two oral contraceptives for 21 days did not influence the plasma concentration-time curve of unchanged nifedipine, mean AUC0–23.5 h and the mean Cmax values of dehydronifedipine were significantly lower in both groups tested/(24% in group A and 25% in group B). This observation may indicate a reduced formation rate of metabolites and reflects an inhibition of cytochrome P450 3A4 activity. The activation of the same or other metabolic degradation mechanism(s) could explain this result.
Conclusion: The investigation presented demonstrates the importance of metabolite measurement when in vivo studies are undertaken to investigate different influences on drug metabolizing ability.
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Received: 2 February 1998 / Accepted in revised form: 12 August 1998
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Balogh, A., Gessinger, S., Svarovsky, U. et al. Can oral contraceptive steroids influence the elimination of nifedipine and its primary pryidine metabolite in humans?. E J Clin Pharmacol 54, 729–734 (1998). https://doi.org/10.1007/s002280050543
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DOI: https://doi.org/10.1007/s002280050543