Effect of Medroxyprogesterone Acetate on the Control of Breathing

Patients with severe chronic obstructive pulmonary disease (COPD) are often not capable to keep bloodgas values at a normal level, they are hypoxaemic and/or hypercapnic. During sleep these patients are even more hypoxaemic and /or hypercapnic due to hypoventilation, especially during the REM state (Vos, 1992). To improve bloodgas values respiratory stimulants such as medroxyprogesterone acetate (MPA) can be used. The mechanisms by which MPA achieve the ventilatory effects are not well understood. Several mechanisms are described. A. Stimulation via progesterone receptors present in the optic area, N. Suprachiasmaticus and the eminentia mediana of the hypothalamus, which even can be potentiated by estrogen. This is described by Bayliss et al., 1987, who found a diminished effect of progesterone after midcollicular decerebration of cats, while the effect remained preserved after decortication. B. Stimulation via the peripheral and central chemoreflexloops. Zwillich et al., 1978 found an increase in gain of the ventilatory CO2 response curve indicating stimulation of ventilation by chemical route. C. An effect of progesterone on muscular receptors. Hensley et al.,198̈0 found a reduction of upper airway obstruction in patients, possibly by promoting motor activity of the upper-airway muscles.