Blood platelet cyclic AMP during long-term treatment of premature labor.

The mean platelet cyclic AMP (cAMP) value in normal pregnant women between 20 and 37 weeks of gestation was 8.2 +/- 0.4 (SEM) pmol cAMP/10(9) platelets (n = 100). From 35 patients with premature labor, 81 blood samples were obtained from measurement of the platelet cAMP before, during and after treatment with fenoterol/verapamil. During the first 4 days of therapy there was an increase of cAMP (p < 0.005); with long-term therapy the blood platelet cAMP was decreased (p < 0.005). Because platelet aggregation has a negative correlation with platelet cAMP, fenoterol should be used cautiously in patients with defective platelet function, in severe bleeding, and before surgery. With long-term treatment platelet aggregation may be increased and thus contribute to the formation of thrombi. Placental perfusion is not likely to be improved by increased platelet aggregation during long-term treatment with fenoterol.