Respiration effect of synthetic progestin in small doses in normal men

Twelve healthy men were studied to determine the effect of ventilatory stimulation with chlormadinone acetate (CMA), a potent synthetic progesterone, in small doses (5 mg/day), on arterial blood gas levels. Using a randomized, double-blind, crossover trial, one week of CMA administration caused a significant reduction in arterial CO2 tension (PaCO2) by 4.1 +/- 2.9 (SD) mm Hg. The magnitude of the fall in PaCO2 was about the same as that obtained with dose of 50 mg per day in our previous study. The results indicate that the dosages of progestin and the effect of the drug on ventilation were not in parallel, and it may provide the idea that larger doses of progestin would not necessarily be required to stimulate ventilation.