Effects of oral contraceptives containing different progestogens on sodium-lithium countertransport in normal females.
In view of the lack of unanimity on the effect of long-term intake of combined oral contraceptives (OC) on external sodium-dependent lithium efflux, otherwise known as sodium-lithium countertransport (SLC), we undertook a double-blind study to investigate the possible interaction between SLC and OC in healthy women with regular menstrual cycles. In a group of 17 volunteers, aged 27.0 +/- 1.1 years (mean +/- s.e.m.) and weighing 61.4 +/- 2.0 kg, ingestion of 30 microg ethinyloestradiol + 150 microg desogestrel for 3 months caused an increase in SLC activity from a baseline value of 0.254 +/- 0.017 mmol/lcell x h to 0.274 +/- 0.017 mmol/lcell x h (P = 0.05). The activity of the transport system after 6 months treatment remained higher than at baseline (0.280 +/- 0.016 mmol/lcell x h, P < 0.025) but was comparable to that at 3 months. Blood pressure and weight remained unaltered during the study period. In a comparable group of 16 volunteers of age 26.1 +/- 1.3 years and weight 63.5 +/- 2.1 kg, control SLC activity (0.218 +/- 0.012 mmol/lcell x h) was comparable to that after 3 months (0.215 +/- 0.011 mmol/lcell x h) and 6 months (0.216 +/- 0.011 mmol/lcell x h) intake of 35 microg ethinyloestradiol + 2 mg cyproterone acetate. Body weight and blood pressure remained similarly unchanged. These results not only confirm that long-term intake of OC may cause increased SLC activity, but also suggest that the type of the progesterone in the medication used could be an important determinant of such interaction.
Adebayo
G I
GI
Department of Therapeutics, TCD Medical School, Trinity Centre for Health Science, St James's Hospital, Dublin, Eire.
Norris
L
L
Devitt
M
M
Bonnar
J
J
Feely
J
J
D000293:Adolescent; D000328:Adult; D017920:Antiporters / Q000187:drug effects*; D003276:Contraceptives, Oral / Q000494:pharmacology*; D017373:Cyproterone Acetate / Q000494:pharmacology*; D017135:Desogestrel / Q000494:pharmacology*; D004311:Double-Blind Method; D004338:Drug Combinations; D045166:Estradiol Congeners / Q000494:pharmacology*; D004997:Ethinyl Estradiol / Q000494:pharmacology*; D005260:Female; D006801:Humans; D045167:Progesterone Congeners / Q000494:pharmacology*; D012016:Reference Values
D017920:Antiporters; D003276:Contraceptives, Oral; D004338:Drug Combinations; D045166:Estradiol Congeners; D045167:Progesterone Congeners; C045885:sodium-lithium countertransporter; D004997:Ethinyl Estradiol; D017373:Cyproterone Acetate; D017135:Desogestrel