Effects of seven low-dose combined contraceptives on vitamin B6 status

The effect of seven low-dose oral contraceptive preparations on vitamin B6 status was investigated in 55 women. All preparations contained about the same amount of ethinylestradiol but differed in the content and type of progestagen. The following preparations were investigated: monophasic and triphasic levonorgestrel, monophasic and biphasic desogestrel, monophasic norethisterone, monophasic cyproterone acetate and triphasic gestodene. The vitamin B6 status was evaluated by measuring erythrocyte glutamate oxaloacetate transaminase (EGOT) activity and its degree of in vitro stimulation. From these two variables the total EGOT activity was calculated. In addition plasma pyridoxal-5'-phosphate (PLP) levels were estimated. After six months' treatment, EGOT activity and the calculated total EGOT activity were increased, but no changes were observed in the degree of in vitro stimulation (which is a more reliable parameter). Plasma PLP levels initially decreased during the first three months of treatment but after six months a return to normal levels was observed. Differences between the seven preparations were not found. We conclude from these results that the low-dose preparations investigated in this study have no any adverse effects on vitamin B6 status.