Thiamine status and oral contraceptives.
A study on thiamine status associated with oral contraceptive (OC) therapy is presented. Blood samples were obtained from 20 healthy young women prior to OC therapy (Minovlar, 1-mg norethisterone acetate plus 50-mcg ethinyl estradiol or Nordiol, .25-mg d-norgestrel plus 50-mcg ethinyl estradiol) and again at the end of the third treatment cycle. Transketolase activity was measured on lysed erythrocytes with and without excess thiamine pyrophosphate. The increase in enzyme activity in the presence of excess thiamine pyrophosphate was calculated as a percentage of the basal measurement. Transketolase activity was stimulated by excess thiamine pyrophosphate in pretreatment samples, however, the stimulation was significantly greater in the treatment samples (p less than .005), indicating the induction of a mild thiamine hypovitaminosis by OCs. It is concluded that there should be regular Viatmin-C and Vitamin-B supplementation for women taking OCs.