Adapted from Current Therapeutics August 1994 by Sue Bagshaw
(Manager Medical Services, NZ Family Planning Association Southern Region ,Christchurch, New Zealand)
Side effects of COC may be classified into two groups. Those that do not happen very often but are more serious and perhaps could be considered as risks, in that, they may seriously affect the health of the user, and those side effects which happen more often, but which are not such a threat to health.
Ø coagulation, Thromboembolisme
The way in which the COC affects coagulation is complex and is affected not only by changes in oestrogen dose, but also by the dose and type of progestogen. The COC interfere with coagulation at multiple points. There is an increase in the production of factors involved in the clotting pathway, e.g. factors VII, VIII, IX, X, XII, fibrinogen and prothrombin. However, there is also an effect on the anticoagulant pathway, with a decrease in anti thrombin III, total protein S, and an increase in protein c. In addition, the production of prostacyclin is reduced and platelet aggregation is increased. These effects are more marked with high oestrogen dose. It cannot be said that the low dose pill not effect coagulation, but certainly is much less.
Ø myocardial infarction
Death of a segment of heart muscle, which follows interruption of its blood supply. Myocardial infarction is usually confined to the left ventricle. The patient experiences the ‘heart attack’: sudden severe chest pain, which may spread to the arms and throat. The main danger is that of ventricular fibrillation, which accounts for most of the fatalities. Other arrhythmias are also frequent; ectopic beats in the ventricle are especially important as they predispose to ventricular fibrillation. Other complications include heart failure, rupture of the heart, phlebothrombosis, pulmonary embolisme, pericarditis, shock, mitral incompetence, and perforation of the septum between the ventricles.
The best results from the management of the patients with myocardial infarction follow mobile and hospital-based coronary care with facilities for the early detection, prevention, and treatment of arrhythmias and cardiac arrest. Most survivors of myocardial infarction are able to return to a full and active life, including those who have been successfully resuscitated from cardiac arrest.
Ø hypertension
The Combined Oral Contraceptive (COC) causes a slight rise in blood pressure of most women. This is usually no more than about 5mm Hg. About 4-5% may become hypertensive. Blood pressure usually decreases as soon as the COC discontinued. Why this situation happens is unclear. The effect is more mark in women who are older and who have a past or family history of hypertension. It may be that it is both an oestrogen and progestogen effect.
Ø Breast cancer
Although COC protects from benign breast disease but there seems to be some increase in the risk of breast cancer. It may be that the protective effect on benign disease is restricted to the less serious forms of disease in which epithelial atypia are minimal.
The most concerning of the recent studies show an increased with increasing use before first term pregnancy and under 25 years of age. However this studies all involved the higher dose pills and did not take into account types of progestogen use. It is probably reasonable to suppose that lower dose pills would be associated with lower risk.
One way of clarifying the degree of risk involved with COC use to patients, is to explain that if 1000 women under 35 were to be examined for breast cancer 2 might have it. If all these women were to use the COC for 8 years under the age of 25 the there might be three women with breast cancer when they were all examined again.
Ø Cervix Uteri cancer
An increasing in cervical cancer have been shown in women using the Combined Oral Contraceptive (COC) for longer than six years. In the Oxford/FPA study 6838 parous women using the COC were compared to 3154 parous women using the IUD. Risk factor and frequency of cervical cytology were similar in both groups. 13 cases of invasive cancer had developed in a 10-year follow-up study. All were in the COC group (Vessey 1989). The incidence of all forms of neoplasia rose from 0.9 per 1000 woman-years after 2 years of COC use, to 2.2 per1000 woman-years after 8 years of use. IUD users fluctuated around 1.0 per 1000 women-years. There have been conflicting results as to whether COC use speeds up development of mild dyplasia to cancer. It is important to be aware of the difficulties involved in controlling for confounding factors like cigarette smoking and number of sexual partners. Overall, there may be a slight increase in risk after 5 to eight years COC use and it seems wise to advise regular cytological screening.