The effects of two phasic oral contraceptives on hemostasis and platelet function

Hemostatic effects of third- and second-generation oral contraceptives: absence of a causal mechanism for a difference in risk of venous thromboembolism

Some observational studies have found a difference in the risk of nonfatal venous thromboembolism (VTE) with low-dose, oral contraceptives (OCs) containing desogestrel (DSG) or gestodene (GSD) and those containing levonorgestrel (LNG). However, this does not agree with current pathophysiological concepts. This review compares all 17 comparative studies on the hemostatic effects of DSG/GSD- and LNG- or norgestimate (NGM)-containing OCs, and comments on two recent cross-sectional studies on the effects of third- and second-generation OCs on activated protein C (APC) sensitivity. In the comparative studies, the only difference in hemostatic parameters between DSG/GSD- and LNG- or NGM-containing OC users was a tendency towards higher factor VII (FVII) levels with DSG/GSD OCs. Differential effects on APC sensitivity were observed with the endogenous thrombin generation potential (ETP) assay, but not with the classical APC resistance test. FVII is not a risk marker for VTE, but is affected by dietary fat, estrogens and androgens and may interfere with the ETP assay. As no differences in established VTE risk markers were observed, there is no plausible reason for a differential risk of VTE with DSG/GSD- and LNG-containing OCs. In fact, the lack of differences with regard to established risk markers of VTE gives further support to the findings of the most recent epidemiological studies, which have not found any difference in the risk of VTE between third- and second-generation OCs.

An open label, randomized study to evaluate the effects of seven monophasic oral contraceptive regimens on hemostatic variables. Outline of the protocol. Oral Contraceptive and Hemostasis Study Group

Complementary to the epidemiological knowledge on the association between oral contraceptive use and the occurrence of venous thromboembolism, a study was designed to obtain more conclusive data regarding the effect of estrogen dose and progestogen type of oral contraceptives on risk markers for the occurrence of venous thromboembolism. The protocol for this multicenter, randomized, open label, parallel group, comparative study is outlined in the present article. A total of 730 healthy, nonsmoking, mulliparous women were treated for six cycles with one of the seven monophasic oral contraceptives tested in this study. The effects of progestogen type (desogestrel, gestodene, levonorgestrel, and norgestimate) and the effects of ethinyl estradiol dose (50, 30, and 20 micrograms) on various hemostatic variables was assessed, including the key components of the anticoagulant and fibrinolytic system, as well as the coagulation system. The primary outcome variables in the study were prothrombin fragment 1 + 2 and D-dimer.

Effects on hemostatic variables of desogestrel- and gestodene-containing oral contraceptives in comparison with levonorgestrel-containing oral contraceptives: a review

In some studies third-generation oral contraceptives have been reported to be associated with a higher risk of venous thromboembolism than are second-generation oral contraceptives, whereas recent, more refined studies have not confirmed this. The reasons for the alleged differences are under discussion, and differential effects on hemostasis have been proposed. Eighteen studies comparing second- and third-generation oral contraceptives with respect to their effects on hemostasis were analyzed. Significant changes from baseline were reported for many variables with both second- and third-generation oral contraceptives without significant between-group differences. Also, in a combined analysis of nonsignificant changes, no consistent pattern of change emerged for any marker, with the exception of higher factor VII levels associated with third-generation oral contraceptives. However, factor VII is not related to venous thromboembolism risk. In addition, 1 cross-sectional study with an unvalidated assay reported a higher ratio of activated protein C sensitivity with third-generation oral contraceptives. Only 2 components of the hemostatic system (factor VII and activated protein C sensitivity ratio) emerged as potentially differentially affected by second- and third-generation oral contraceptives; the association with venous thromboembolism risk is questionable in the former case and unknown in the latter.

Effects of dienogest (a synthetic steroid) on coagulation, fibrinolysis, and platelet aggregation in female monkeys

We investigated the effects of dienogest (0.1-10 mg/kg per day, p.o.) on coagulation, fibrinolysis and platelet aggregation in female rhesus monkeys. Then, we also examined those of medroxyprogesterone acetate (MPA, 10 mg/kg per day, p.o.) or danazol (10-1000 mg/kg per day, p.o.) on these parameters in the same species. In addition, we assessed the effects of dienogest (1 and 3 mg/kg per day, p.o.) or MPA (10 mg/kg per day, p.o.) on platelet aggregation and platelet lipids in female cynomolgus monkeys. At doses of 0.3 mg/kg or greater, dienogest increased the levels of several coagulation and anticoagulation factors, but had no effect on the prothrombin time, activated partial thromboplastin time, fibrinolysis, or platelet aggregation. MPA (10 mg/kg) had no effect on coagulation or fibrinolysis, but significantly potentiated platelet aggregation in response to ADP and collagen and also increased the platelet cholesterol-to-phospholipid ratio. Danazol (10 mg/kg or more) increased the activities of coagulation factors V, VII, VIII, X, XI, and XII in comparison to dienogest and MPA. Consequently, dienogest caused less potentiation of platelet aggregation than MPA and less potentiation of coagulation than danazol.

Haemostatic changes and the oral contraceptive pill

Oral contraceptives have been linked to an increased incidence of thrombovascular disease. This may be mediated by their effects on the haemostatic system. An increase in the activity of coagulation Factors VII, X and fibrinogen occur with pill usage. Increased Factor VII levels are dependent on both the oestrogen and progestogen component of the oral contraceptive. A reduction in antithrombin III levels has also been observed in some but not all studies. Increased fibrinolysis has also been shown in oral contraceptive users which should balance the changes in the coagulation pathway. The increase in fibrinolytic potential is thought to be due to a decrease in the levels of plasminogen activator inhibitor I combined with an increase in the levels of plasminogen; tissue plasminogen activator antigen is decreased in most studies. The increased levels of endpoints of coagulation and fibrinolysis in pill users indicate that enhanced activity of both systems is occurring in vivo. The increased coagulation activity appears to be balanced by the rise in fibrinolytic activity, so preserving haemostatic balance. Enhanced platelet activity has also been shown in women taking oral contraceptives. Thrombus formation can result, however, when local vascular wall damage exists, or when other risk factors for thrombo-embolism, such as older age and smoking, coexist and create a local activation resulting in a thrombus. In these situations, the small differences in levels of coagulation factors in women taking different oral contraceptive formulations may be important. Pills containing the lowest doses of oestrogen (20 micrograms ethinyloestradiol) have shown the least changes in haemostatic factors. The progestogen component of the pill modifies the effect of oestrogen on the haemostatic system.