oa SA Pharmaceutical Journal - The safety and efficacy of low-dose oral contraceptives : medifile
Oral contraceptives (OCs) are classified according to the dosage of ethinyloestradiol (EE), the type of progestogen and whether the dosages of EE and progestogen stay the same during the cycle or change in a phasic manner. Ultimately, there is no statistically significant difference in efficacy between high-dose and low-dose OCs. There is also no difference in efficacy between monophasic and multiphasic products, which, other than lower hormone content, have no benefit over monophasic products.
Several medications, such as rifampicin, some of the anticonvulsants and certain HIV medications, may reduce the efficacy of OCs and higher dose OC preparations are recommended in patients taking these concomitant drugs.
The effectiveness of OCs with typical use is largely dependent on compliance, which is influenced by bleeding patterns and side-effects. In this regard, the composition of the OC may play a significant role.The dosage of EE and type of progestogen may relate to specific noncontraceptive benefits, such as improvement in dysfunctional uterine bleeding, dysmenorrhoea, premenstrual tension, endometriosis, iron deficiency anaemia, hyperandrogenism and acne. The 3rd generation progestogens and antiandrogens are generally regarded as more ''skin friendly''.
The cardiovascular safety of OCs has long been controversial and although complications such as myocardial infarction and stroke have been reduced over the years with lower EE dosages, the risk of venous thromboembolism (VTE) has not decreased consistently. In fact, some of the low-dose products containing 3rd generation progestogens and antiandrogens may be associated with a higher risk of VTE.
Breast cancer is another controversial issue associated with OC use. Epidemiological studies do not report an increased risk, whereas other meta-analyses do. The risk may be amplified by genetic susceptibility, although data on the subject are not consistent.
An increased risk of hepatic adenoma and cervical cancer has also been noted with OC use, but the latter seems to be dependent on persistent human papilloma virus infection. On the other hand, ovarian and endometrial cancer is reduced by the use of OCs, although genetic susceptibility may also modify the risk.
As indicated by several studies on risk factors related to the safety of contraceptives, the choice of contraceptive is more complicated in patients with certain medical conditions, seeing that physiologic changes and side-effects associated with the method may increase the risk of morbidity / mortality in these women. All women requesting contraceptives should have a risk-benefit assessment before starting on any contraceptive to ensure the safety of the method. This is also true for OCs and in this regard the latest World Health Organization safety categories may be consulted.
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