Wk 1 Drugs for contraception

Question 1

How pharmacotherapeutic agents modify fertility?

Answer 1

• ovulation: oestrogen suppress ovulation process (suppress FSH hormone)
• implantation: progestogen thicken cervical mucus

Question 2

Describe the use of different contraceptive agents (including benefits)

Answer 2

COC: combined oral contraceptives
NP: oestrogen & progestogen, take daily for 21~28 days (7 placebos in 28 pack to help with adherence), withdrawal bleeding can occur on placebo days
MOA:
- oestrogen - suppress FSH → prevents development of dominant follicle
- progestogen - suppress LH → block ovulation, - thicken cervical mucus
Benefits:
- regulation of menstrual bleeding
- light AEs, less painful
- less risk of endometrial cancer
AEs:
- breakthrough bleeding
- breast tenderness
Metabolic effects:
- ↑ HDL, ↓ LDL
- ↑ coagulation factors (risk of stroke)
Interactions: CYP3A4 inducers (rifampicin, phenytoin, carbamazepine), grapefruit juice, St John’s Wort
Practice point: take daily, N/V ↓ efficacy

Progesterone-only
NP: less effective, effective within 48 hrs, need to take continuously (no placebo)
MOA: thicken cervical mucus - more difficult for sperm to swim through
Benefits: useful when COC is contraindicated, eg breastfeeding (oestrogen ↓ milk), history of VTE
AEs:
- menstrual irregularities
- breast tenderness
- weight gain
Practice point:
- start 1st day of menstruation, or anytime for 48 hrs
- N/V ↓ efficacy

Emergency contraceptives:
NP: within 72 hrs
Benefits: convenient
AEs: vomiting
Practice point: N/V ↓ efficacy

Question 3

Discuss the factors for consideration in the choice of contraceptive

Answer 3

• COC is the most reliable but has risks of stroke vaginal bleeding
• Progestogen-only can be used as an alternative when COC is not tolerated or PT has high stroke risk