Contraception 3

Question 1

Why are oral combined hormonal contraceptives associated with increased risk of thromboembolic complications?

Answer 1

• 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

Question 2

What is the uterine first pass effect?

Answer 2

• 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