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Contraceptives

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الكلية كلية الطب     القسم  الادوية     المرحلة 3
أستاذ المادة انتصار جواد حمد المختار       21/06/2018 13:41:36
Contraceptives
Dr. Entisar Al-Mukhtar
Contraceptives
Interference with ovulation is the most common pharmacologic intervention for prevention of pregnancy.

Major classes of contraceptives
1. Combination oral contraceptives (COCPs):
• Containing a combination of an estrogen & a progestin are the most common type of oral contraceptive (OC).
• COCPs are highly effective.
• Monophasic combination pills contain a constant dose of estrogen & progestin.
• Triphasic OC mimic the natural female cycle & most contain a constant dose of estrogen with increasing doses of progestin given over 3 successive 7-day periods.
• The active pills are taken for 21-24 days, followed by 4-7 days of placebo.
• Withdrawal bleeding occurs during the hormone-free (placebo) interval.
• Note: Ethinyl estradiol is the most common estrogen in COCPs & the most common progestins are norethindrone, norethindrone acetate, levonorgestrel, desogestrel, norgestimate & drospirenone.
• An extended-cycle contraception (84 active pills followed by 7 days of placebo) results in less frequent withdrawal bleeding.
• A continuous OC product (active pills taken every day) is also available.

2. Transdermal patch contraceptive:
• An alternative to COCPs.
• Containing ethinyl estradiol & norelgestromin (progestin).
• One patch is applied each week for 3 weeks to the abdomen, upper torso, or buttock. At week 4 (patch free) withdrawal bleeding occurs.
• Its efficacy is comparable to the OC efficacy, but it is less effective in women weighing > 90 kg.
• Contraindications & adverse effects are similar to those of OC.
• Risk of adverse events such as thromboembolism with the transdermal patch is greater than that seen with OC.

3. Vaginal ring:
• Containing ethinyl estradiol & etonogestrel.
• A ring is inserted into the vagina & left for 3 weeks, at week 4 (ring free) withdrawal bleeding occurs.
• Efficacy, contraindications & adverse effects like those of COCPs.
• vaginal ring caveat is that it may occasionally slip or be expelled accidentally.

4. Progestin-only pills (mini-pill):
• Usually containing, norethindrone & are taken daily on a continuous schedule.
• less effective than COCPs & may produce irregular menstrual cycles more frequently.
• Used for patients who are breastfeeding (unlike estrogen, progestins do not affect milk production), intolerant to estrogen, smokers, or have other contraindications to estrogen.

5. Injectable progestin:
• Medroxyprogesterone acetate is available in both IM & SC formulations injected every 3 months.
• Medroxyprogesterone acetate adverse effect: weight gain, amenorrhea, return to fertility may be delayed for several months.
• It should not be continued for more than 2 years because patients may predispose to osteoporosis and/or fractures.

6. Progestin implants:
• An etonogestrel containing implant placed subdermally in the upper arm, it provides about 3 years of contraception.
• Implant is reliable as sterilization & effect is reversible after surgical remove.

7. Progestin intrauterine device:
• A Levonorgestrel-releasing intrauterine system, provides 3-5 years contraception.
• Suitable for women who having contraindications to estrogen.
• Should be avoided in patients with pelvic inflammatory disease or a history of
ectopic pregnancy.

8. Postcoital (emergency) contraception:
• High doses of levonorgestrel (eg. 0.75 mg) or high doses of ethinyl estradiol (100 ?g) plus levonorgestrel (0.5 mg) are administered as soon as possible preferably within 72 hours of unprotected intercourse (the “morning-after pill”).
A second dose should be taken 12 hours after the first dose.
• A newer progestin-only regimen consists of a one-time dose of 1.5 mg levonorgestrel.
• The ulipristal (a progesterone agonist/antagonist) is indicated as emergency contraceptive within 5 days of unprotected intercourse.
MOA:
Estrogen provides a negative feedback on the LH & FSH release, thus preventing ovulation. Progestin inhibits LH release & thickens cervical mucus, thus hampering sperm transport. Progestin withdrawal stimulates menstrual bleeding during the placebo week.
Adverse effects:
• Breast fullness, fluid retention, headache & nausea are most common with estrogens. Increased BP may also occur.
• Progestins may cause depression, changes in libido, hirsutism, and acne.
• Although rare, thromboembolism, thrombophlebitis, MI, and stroke may occur with use of OCs especially among smoker women over age 35.
• Cervical cancer incidence may be increased with OCs, because women are less likely to use additional barrier methods of contraception that reduce exposure to human papillomavirus (the primary risk factor for cervical cancer). [Note: OCs are associated with a decreased risk of endometrial & ovarian cancer.]
Contraindications:
1. Cerebrovascular & thromboembolic disease, estrogen-dependent neoplasms, liver
disease and pregnancy.
2. COCPs should not be used by heavy smokers women over the age of 35.

Drug interactions:
1. Rifampin & bosentan induce metabolism of OCs reducing their efficacy (avoid concurrent use, or use an alternate barrier method of contraception).
2. Antibiotics that alter the normal GI flora may reduce enterohepatic recycling of the estrogen (in OCs), thus, an alternate method of contraception is needed.


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