RESUMO
PIP: 73 healthy women (29 controls, 25 using OCs, and 19 using Norplant) were selected from the clinic population at North Oakland Medical Center for inclusion in this study after obtaining informed consent. Age, race, height, weight, blood pressure, and cigarette smoking were recorded for each subject. 12 patients were on monophasic OCs while 13 were on triphasic preparations. Both hormonal contraceptive groups had used their particular contraceptive for at least 3 months prior to blood drawing. Platelet tests were performed within 2 hours of sample collection: platelet counts (PLC) and mean platelet volume (MPV) were determined on an Automated Platelet Counter (Baker 810 Platelet Analyzer). Whole blood aggregation was performed on a platelet aggregometer (Chrono-Log, Model 550) using both ADP (ADP, 5 mM) and collagen (COLL, 2 mcg/ml) as inducing agents. Demographic differences were not significant (p 0.05) among the 3 treatment groups, whose average age was 25.3-25.8 years old. Furthermore, no significant differences (p 0.05) in platelet function were detected among controls or subjects receiving either oral contraceptives or Norplant, compared to control patients. The mean platelet counts (X 10/9/L) were 223 for OC users, 231 for Norplant users, and 232 for controls. The respective platelet aggregation (ADP, ohms) values were 12.5, 18.0, and 19.2 as well as (COLL, ohms) 35.6, 40.7, and 39.0. These results demonstrated that there is no evidence for altered platelet function, with the testing methods employed, in women using either Norplant or combination low dose oral contraceptives. To date, several studies have examined this issue, with contradictory reports about the effects of hormonal contraceptives in platelet function. After controlling for differences between various steroid preparations and other such confounding variables, some of these conflicting conclusions could be the result of a lack of uniformity among the methods used to evaluate platelet aggregation. The ability to draw conclusions regarding altered in vivo thrombotic potential from these studies is thus questionable.^ieng
