Possible Interaction: Ethinyl Estradiol and Vitamin C

“ Ascorbic acid can, therefore, be removed from the list of drugs interfering with the pharmacokinetics of ethinyl estradiol.”

“Previous studies in small numbers of women have suggested that the administration of gram quantities of ascorbic acid interferes with the conversion of ethinyl estradiol (EE2) to its sulfates, leading to higher blood levels of EE2.”

“Two drugs, ascorbic acid (vitamin C) and paracetamol (acetaminophen), give rise to increased blood concentrations of ethinylestradiol due to competition for sulphation.”

“Plasma concentrations of ethinylestradiol may be increased by ascorbic acid (vitamin C) and paracetamol (acetaminophen) which compete with it for sulphation in the gut wall.”

“Plasma ethinylestradiol increases 47.6% when taken with ascorbic acid because of competition in producing sulfate conjugation.”

“Available options are to increase the estrogen dose to as much as 100 mg, to substitute valproic acid for other anticonvulsants, or to augment ethinyl estradiol levels by oral administration of ascorbic acid , which increases the bioavailability of the steroid.”

“Dr. D.J. Back and his colleagues (May 9 p.1516) have shown that ascorbic acid in a dose of 1 g daily increases the plasma concentration of ethinyl estradiol when given to women taking combined (OC) oral contraceptive preparations.”

“If the toxic effects of the enhancement of ethinyloestradiol plasma concentration by ascorbic acid rise in parallel with the therapeutic activity, then the net benefit is nil.”

“If the toxic effects of the enhancement of ethinyloestradiol plasma concentration by ascorbic acid rise in parallel with the therapeutic activity, then the net benefit is nil.”

“If the toxic effects of the enhancement of ethinyloestradiol plasma concentration by ascorbic acid rise in parallel with the therapeutic activity, then the net benefit is nil.”

“In vitro studies revealed a markedly higher rate of oxidation of ascorbic acid in the presence of either estinyl or progestogen than in untreated controls.”

“Oral … either estinyl (5 micrograms) or progestogen (250 … combination with 5 mg of ascorbic acid (minimum requirement) daily for 21 d, resulted in significantly lower (P less than 0.05) concentrations of … acid in plasma, liver, adrenals and urine than in animals receiving only 5 mg of the vitamin.”