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Pharmacology and Toxicology
PHAR 100
Hisham Elbatarny

Contraceptives • History st ◦ 1 contraceptive in Canada came on market in1961 ◦ stumbling block of finding contraceptive: availability of synthetic estrogens + progesterones ◦ allowed development of estrogen: plants ▪ company was able to take plant estradiol, modify it and came up with starting material • hard to synthesize • Social issues ◦ issues with use of contraceptive, oral contraceptive especially ◦ w/ use of contraceptive: sex more accepted ◦ religious issues ◦ gave women power: allowed them to become a more predictable part of the workplace ▪ family planning ◦ gave women economic power: make choice of whether wanted family or fulfill some parts of their career ◦ reduced the family size (avg right now = 1.9) • Medical issues ◦ most drugs used to treat disease ◦ w/ oral contraceptive no longer treating disease, but used to prevent a future outcome (pregnancy) → as a result medical approach must be slightly different • Toxicological issues ◦ safety profile of a drug use for social-economic issues must be quite different ◦ follow toxicity of these compounds quite closely Controlled by hypothalamus that releases hormone that stimulates the pituitary to release LH/FSH -are selective receptors forestrogen and progesterone in hypothalamus, endometrium -during cycle when estrogen (esp.)and progesterone increases, it feedbacks to hypothalamus which releases gonadotropin releasing hormone – no more FSH -LH/FSHstimulates growth offollicles -one ofthemstarts to growmuch more quickly -follicle then secretes estrogen -this stimulates the growth ofthe endometrium(proliferative phase) -at mid cycle, follicle is mature -LHacts on ovary to release follicle and increases release ofestrogen and progesterone -once follicle is released (structure leftover:corpus luteum) -corpus luteumreleases progesterone and estrogen stimulating endometriumto release nutrients (secretory phase) -ifpregnancy doesn't occure, corpus luteumstops secreting progesterone target drugs whereverthere is a receptor and endometriumloses “support” of progesterone -gonadotropin releasing hormone agonist -lining begins to be sloughs and menstruation occurs -inhibit estr/prog in endometrium→ endometriumstops making nutrients Ovarian cycle • beginning of cycle several follicles develop in response to FSH. • days 5 -6 one follicle develops rapidly, and under LH secretes estrogen • proliferation of endometrium • estrogen inhibits release of FSH (no more follicles). • orogesterone secretion increases • secretory phase of endometrium • LH and FSH cause release of ovum • Corpus luteum (site of ovum release) secretes more progesterone and estrogen to maintain the endometrium and pregnancy. • if no implantation corpus luteum regresses and endometrium loses support and menstruation ensues. • cycle is repeated every 28 days or so Ideal Contraceptive • highly effective: approaching 100% effective • safe - no adverse events. • economical • easy to use • high patient acceptance: ◦ agent should not interfere w/ sex (not want agent that takes ½ hour to get ready for sex) ◦ from moral, toxicity, user standpoint • not controversial neverhave just estrogen Hormonal Contraceptives • combined estrogen-progestin preps: most effective ◦ fixed dose of hormones daily from day 5 to 25 of cycle ◦ some taken continually • combined estrogen-varying progestin ◦ phasic preps. start with low dose of progestin and increase dose through out cycle. Or alter dose of estrogen • IUD coated with hormone. • low dose progestin (estrogen contra indicative in some people – ex: blood clots, breast cancer) ◦ progestin taken daily: only recommended for women who can't take estrogen Contraceptive Patch • transdermal system that delivers about 20 mcg of ethinyl estradiol and 150 mcg/day of norelgestromin • patch applied for three cycles of 7 days each and use three patches per menstrual cycle or every 28 days “Came on to • Norplant/Jadelle: progesterone only contraceptive, surgically implanted under skin market w/ big ◦ progestin in a silastic tube – slow release of drug, contraception for 5 years fanfare then crashed and • Depoprovera: medroxy progesterone acetate injected into muscle burned” ◦ injectable progestin – Contraception for 3 months Estrogen-Progestin Combination – Mechanisms of Action • inhibit release of GN/RH from hypothalamus – no ovulation MAIN • progestin alters secretions of endocervical glands – to thick mucus – sperm migration may be inhibited • inappropriate endometrium for implantation -given ethane estradiol feeds back on hypothalamus and acts on the estrogen receptors -inhibiting gonadrotropin releasing hormone, no FHand FSH -don't have a normal endometrium -don't get full proliferative phase -unlikely implantation would occur b/c ofthis Progestin Contraceptives - Mechanism • suppress GN/RH – no ovulation – less effective than estrogen-progestin combinations • some women do ovulate Play greater role • altered endometrium then with • alters secretion of endocervical glands: more viscous and tenacious combination Problems with Low-Dose Progestins • breakthrough bleeding – can be significant (25%) in the first cycle • high failure rate, 2%/year pregnancy rate (at least twice that of the combination) • increase low density lipoproteins ◦ decrease high density lipoproteins ◦ depends on the progestin. Norplant Prob
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