Eficacy of oral contraceptives

Does Folliculogenesis  occurs with low dose formulations of OCP ?? Can escape ovulation occur while on OCP?? Ans: Because   the doses of steroids in currently marked OCs are low ,  neither  gonadotropin production nor ovarian  steroidogenesis   is completely   suppressed.  Complete   absence of  follicular  activity  as was often noted  during high  dose OC use  no longer   occurs. The magnitude of hypothalamic  pituitary   suppression is unrelated  to the age  of the woman or the duration of steroid   use but   is related   to the potency   of the progestin   and estrogen in the formulation. The magnitude of the hypothalamic  pituitary   suppression is correlated with the incidence   and severity of prolonged amenorrhea   after stopping OCs . After discontinuing current   low dose formulations return to ovulation is usually  rapid . However   because the suppression is   so quickly reversible  . There is less room for error  when using  current low dose   OCs. Extending the pill free interval for more than 7 days   may result in break through   ovulation and pregnancy. Women should be  advised  that the most important    pills  to remember   to take are  the first  ones of each cycle. The new low dose OC   Yaz shortens the pill free interval  to 4 days   to potentially increase  effectiveness with typical use .

  Does efficacy decreses with low dose formulations??Ans:  No significant differences in clinical   effectiveness have  been demonstrated for the various combination OCs  currently available. With  perfect use the pregnancy rate is 0.2 -0.3%  at the end  of 1 year with all products  However  the typical use failure  rate  is higher   and varies  between 3 and 8%  depending   on the population . The risk of contraception failure is highest if pills are  missed at the beginning of the cycle . Because   the contraceptive   patch and ring  have basically the same mechanism of action their  perfect and typical   use failure rate is considered  to be the  same as  combination OCs  the contraceptive patch  and ring are very   effective   but are  considered   to be in the second  tier of contraceptive  effectiveness. The first tier methods   intrauterine    devices  implants   and infections have lower  typical failure rates as they   are not as subject to user error.

A recent study suggested   that high body weight  may alter    be metabolism of the steroids in low  dose OCs  enough to reduce their effectiveness   . In a  retrospective   study women weighing more than 90 Kg     taking Oc formulations with less than 50 ug   had a failure   rate 2.6  times greater than   women with   lower body weight   and a 4.5   times greater failure   rate when using formulations  with less than  35 ug   . A lower   contraceptive effectiveness was also   reported in patch users   weighing  more than  100 Kg  . The risks   associated with using a pill with higher   amounts  of EE should be  balanced  against this  possible increased  failure   rate when   deciding   on an appropriate   formulation.