Stimulatory as well as inhibitory effects of ethinyloestradiol on the metabolic clearances of propranolol in young women

1 The metabolism of a single 80 mg oral dose of propranolol was determined in nine young women before and after administration of ethinyloestradiol alone (EE2) or in combination with norethindrone (OC). 2 Whereas the total clearance of propranolol (2713±404 ml min−1 (mean±s.e.mean)) was not significantly altered by either EE2 (3365±347 ml min−1) or the combined OC (2905±345 ml min−1), significant changes in all three primary metabolic pathways were observed. 3 The clearance through side‐chain oxidation decreased from 345±55 ml min−1 to 262±33 ml min−1 after EE2 (P