Plasma ascorbic acid concentrations and oral contraceptives

Abstract

For 110 days plasma and urine concentrations of ascorbic acid were studied in 2 control women and in 4 taking oral contraceptive users. The pills and durations of therapy in years were: 1) 1 mg norethindrone .05 mg mestranol (Ortho-Novum) for less than 2.5; 2) 1 mg ethynodiol diacetate .1 mg mestranol (Ovulen) for less than 1; 3) 5 mg norethynodrel .075 mg mestranol (Enovid-E) for more than 5; and 4) 9.85 mg norethynodrel .15 mg mestranol (Enovid-E) for less than .5. Diet was free except for compulsory orange juice to assure 150 mg ascorbic acid per day determined through the lack of effect of an extra 300 mg dose given for the first 35 days to achieve maximum fasting plasma ascorbic acid concentrations. In the controls plasma levels of ascorbic acid (determined with 26-dichlorophenolindophenol) and total ascorbic acid (determined with 24-dinitrophenylhydrazine) were highest at ovulation (time of high estrogen and luteinizing hormone secretion) lowest in the late secretory phase and menses and moderate in between (during the proliferatory and early secretory phases). The pills prevented cyclic changes in plasma concentrations. The lack of ingestion of pills during menses is believed to cause the higher concentrations observed then for 3 women using oral contraception. The lack of any variation for 1 woman using oral contraception is attributed to her high daily progestin intake. It is suggested that the pills depress plasma concentrations of ascorbic acid. The data suggest a positive correlation between duration of treatment and extent of the depression. Following the administration of 300 mg of ascorbic acid to oral contraception users urinary analysis showed no increased excretion as a result of oral therapy but there is the possibility that decreased tubular reabsorption may occur.