COMBINED ORAL CONTRACEPTIVES Mechanism of action The combined oral contraceptive (COC) pills currently available in the UK are shown in Table 2. They combine an estrogen (ethinylestradiol (EE) in all cases but one) with one of seven progestogens. Aside from secondary contraceptive effects on the cervical mucus and to impede implantation, COCs primarily prevent ovulation. This makes the method highly effective in ‘perfect’ use (Table 1), but it removes the normal menstrual cyle and replaces it with a cycle that is user-produced and based only on the end-organ, . the endometrium. So the withdrawal bleeding has minimal medical significance, can. | Combined hormonal contraception COMBINED ORAL CONTRACEPTIVES Mechanism of action The combined oral contraceptive COC pills currently available in the UK are shown in Table 2. They combine an estrogen ethinylestradiol EE in all cases but one with one of seven progestogens. Aside from secondary contraceptive effects on the cervical mucus and to impede implantation COCs primarily prevent ovulation. This makes the method highly effective in perfect use Table 1 but it removes the normal menstrual cyle and replaces it with a cycle that is user-produced and based only on the end-organ . the endometrium. So the withdrawal bleeding has minimal medical significance can be deliberately postponed or made infrequent . tricycling discussed below and if it fails to occur once pregnancy is excluded poses no problem. The pill-free time is the contraception-deficient time which has great relevance to advice for the maintenance of COC efficacy see below . Benefits versus risks Capable of providing virtually 100 protection from unwanted pregnancy and taken at a time unconnected with sexual activity the COC provides enormous reassurance by the associated regular short light and usually painless withdrawal bleeding at the end of the 21-day pack. Inevitably most of this section will 11 Table 2 Formulations of currently marketed combined oral contraceptives COCs a Pill type Preparation Estrogen Progestogen pg pg Monophasic Ethinylestradiol Loestrin 20 20 1000 Norethisterone norethisterone type acetate Loestrin 30 30 1500 Norethisterone acetate Brevinor 35 500 Norethisterone Ovysmen 35 500 Norethisterone Norimin 35 1000 Norethisterone Ethinylestradiol Microgynon 30 30 150 levonorgestrel also ED Ovranette 30 150 Ethinylestradiol Mercilon 20 150 desogestrel Marvelon 30 150 Ethinylestradiol Femodette 20 75 gestodene Ethinylestradiol Femodene also ED 30 75 gestodene Minulet 30 75 Ethinylestradiol Cilest 35 250 norgestimate Ethinylestradiol Yasmin 30 3000 drospirenone Mestranol Norinyl-1
