Contraception 3 Flashcards
Using the concept of first pass metabolism, explain why oral combined hormonal contraception is associated with increased risk of thromboembolic complications compared to trans-dermal and vaginal combined hormonal formulations.
1
Q
Why are oral combined hormonal contraceptives associated with increased risk of thromboembolic complications?
A
- Blood from intestines passes through the liver first
- Estrogen and progesterone molecules are metabolized before the blood gets to the rest of the body
- Liver “sees” much higher drug levels than the rest of the body
- Trans-dermal and vaginal combined hormonal formulations bypass this mechanism
2
Q
What is the uterine first pass effect?
A
- Vaginal administration of P and E2
- Preferential distribution to uterus
- Evidence
- uterine tissue P > plasma P
- uterine vascular P > radial artery P
- creates secretory endometrium despite low plasma P
- endometrial P higher after vaginal vs. IM
- higher endometrial E2 levels after vaginal vs. oral E2
