There are many different formulations or brands, but the average pack is designed to be taken over a 28-day period (also known as a cycle). For the first 21 days of the cycle, users take a daily pill that contains two hormones, estrogen and progestogen. During the last 7 days of the cycle, users take daily placebo (biologically inactive) pills and these days are considered hormone-free days. Although these are hormone-free days, users are still protected from pregnancy during this time. Some COCP packs only contain 21 pills and users are advised to take no pills for the last 7 days of the cycle. Other COCP formulations contain 91 pills, consisting of 84 days of active hormones followed by 7 days of placebo (Seasonale). Of recent innovation, COCP formulations can contain 24 days of active hormone pills followed by 4 days of placebo pills (e.g. Yaz 28 and Loestrin 24 Fe) as a means to decrease the severity of placebo effects. These COCPs containing active hormones and a placebo/hormone-free period are called cyclic COCPs. Once a pack of cyclical COCP treatment is completed, users start a new pack and new cycle.Most monophasic COCPs can be used continuously such that patients can skip placebo days and continuously take hormone active pills from a COCP pack. One of the most common reasons users do this is to avoid or diminish withdrawal bleeding.
Women have experienced amenorrhea, easy administration, and improvement in sexual function in some patients.Nausea, vomiting, headache, bloating, breast tenderness, swelling of the ankles/feet (fluid retention), or weight change may occur. Vaginal bleeding between periods (spotting) or missed/irregular periods may occur, especially during the first few months of use. Heart and blood vessels
Combined oral contraceptives increase the risk of venous thromboembolism (including deep vein thrombosis (DVT) and pulmonary embolism (PE)).While lower doses of estrogen in COC pills may have a lower risk of stroke and myocardial infarction compared to higher estrogen dose pills (50 μg/day), users of low estrogen dose COC pills still have an increased risk compared to non-users. These risks are greatest in women with additional risk factors, such as smoking (which increases risk substantially) and long-continued use of the pill, especially in women over 35 years of age.The overall absolute risk of venous thrombosis per 100,000 woman-years in current use of combined oral contraceptives is approximately 60, compared with 30 in non-users. The risk of thromboembolism varies with different types of birth control pills; compared with combined oral contraceptives containing levonorgestrel (LNG), and with the same dose of estrogen and duration of use, the rate ratio of deep venous thrombosis for combined oral contraceptives with norethisterone is 0.98, with norgestimate 1.19, with desogestrel (DSG) 1.82, with gestodene 1.86, with drospirenone (DRSP) 1.64, and with cyproterone acetate 1.88.