Contraception Flashcards
(44 cards)
Methods that prevent ovulation
Combined hormonal contraceptives, contraceptive implant, contraceptive injection
Methods that prevent fertilization
Abstinence, fertility awareness methods, intrauterine device, progestin only pill, barrier methods, spermicides, withdraw, sterilization
Methods that prevent implantation
Secondary mechanism for hormonal contraception and IUDs
Combined hormonal methods (CHC)
Estrogen plus progestin –> prevent ovulation and thicken cervical mucous
Three formations: the pill, transdermal patch, vaginal ring
How does CHC prevent ovulation?
Progestin in the dominant hormone –> diminishes frequency of hypothalamic GnRH pulse frequency and inhibits the estrogen induced LH surge at mid-cycle
Estrogen suppresses FSH preventing selection and emergence of dominant follicle
Progestin pill formulations
Norethindrone (1st generation)
Norgestimate, desogestrel (3rd gen)
Norgestrel, levonorgestrel (2nd gen)
Drospirenone (4th gen)
How does the combined contraceptive vaginal ring prevent ovulation?
Ethylene vinyl acetate ring
Deliveres 15 mcg ethinyl estradiol and 120 mcg etonogestrel
Single ring, vaginally 3 weeks, removed for one week to allow withdrawal bleed
How does the combined transdermal patch prevent ovulation?
20cm^2 patch delivers 20 mug of ethanol estradiol and norelgestromin
One patch per week for 3 weeks then one patch free week
Less effective in women >90 kg/m^2
May have higher rate of VTE
How do combined hormonal contraceptives increase the risk of VTE?
Increases levels of pro-coagulant factors II, VII, VIII, X and fibrinogen
Decrease anticoagulants protein S, anti-thrombin, and tissue factor pathway inhibitor
Induce resistance to the natural anticoagulant activated protein C
CI to CHC
History of VTE, inherited or acquired thrombophilia Postpartum - initial 3-6 weeks History of MI or CAD History of cerebrovascular accident Cigarette smokers > age 35 Complicated diabetes, vascular disease Severe htn BP > 160/100 Migraine with aura Severe active liver disease, cirrhosis, history of hepatic adenoma Personal history of breast or endometrial cancer Undiagnosed abnormal uterine bleeding Pregnancy
Progestin only methods
Pills
Injection
Subdermal implant
How do progestin only pills work?
Ovulation suppressed in 50% of cycles
Prevent fertilization from thickening of cervical mucus and slowing ovum transport through decreased tubal motility
Possibly prevent implantation from thinning of endometrium
Effects are time dependent – for maximal efficacy needs to be taken at the same time every day
Unscheduled bleeding can occur
How does Depot medroxyprogesterone acetate injections work?
Profound ovulation inhibition – slow return to baseline fertility – 7-10 months
Given every 12 weeks
High efficacy
Unscheduled bleeding with trend toward amenorrhea
Reversible decrease in bone density, no evidence of fracture risk
Unaffected by hepatic enzyme inducing drugs
Decreases frequency of seizures and sickle cell crises
How does the contraceptive implant work?
Inhibits ovulation
Single rod – contains progestin etonogestrel
Effective for 3 years
Most effective reversible method
Irregular bleeding is most common adverse effect
How are estrogens and progestin metabolized?
Hepatic cytochrome p450 3A4
What are some cytochrome p450 3A4 inducing medications?
Rifampin (antibiotic) Griseofulvin (antifungal) St. Johns Wort Modafinil Some HIV protease inhibitors Nevirapine - non-nucleoside reverse transcriptase inhibitor
What are some cytochrome p450 3A4 inducing anti-epileptics?
Pheytoin
Carbamazepine
Phenobarbital
Primodone
Topiramate
Felbamat
Vigabatron
What are some anti-epileptics that have no effect on cytochrome p450 3A4?
Valproate
Gabapentin
Lamotrigine
Tiagabine
How do IUDs work?
Highly effective
Two types = Copper and progestin levonorgestrel (5 year and 3 year)
Placed quickly and easily in the office without anesthesia
DO NOT increase risk for infertility
Safe in nulliparous women and teens
Mechanism of Copper T IUD
Prevents normal fertilization
Cu+ ions reduce motility and viability of sperm, toxic to oocytes
Also inhibits implantation, especially if used for emergency contraception
5 year levonorgestrel IUD
Prevents fertilization
Thick impenetrable cervical mucus
Sterile inflammatory reaction within uterus
Impaired sperm migration
Highly effective
FDA approved to treat abnormal uterine bleeding
3 year levonorgestrel IUD
Mechanism same as 5 year Smaller size of device and inserter Contains lower dose of levonorgestrel Designed for teens and nulliparous women Lower rates of amenorrhea
Contraindications to IUD/IUS use
Pregnancy
Pelvic inflammatory disease (current or w/i past 3 months)
Current STI
Puerperal or postabortion sepsis current or within the past 3 months
Purulent cervicitis
Undiagnosed abnormal genital bleeding
malignancy of the genital tract
Known uterine anomalies or fibroids distorting the cavity in a way incompatible with IUD insertion
Allergy to any component of the IUD or Wilson’s disease (for copper)
How does a male condom work?
Prevents fertilization
Reduces risk of STI transmission
Typical use failure rate first year 18%
Perfect use failure rate first year 3%
Latex, polyurethane and natural membrane
3-5% breakage or slippage rate – consider use of emergency contraception as back up
Use only water based lubricants with latex
