SOME OTHER DRUGS

1. Dinoprostone (PGE₂)

Core action

• Prostaglandin E₂ analogue → prepares cervix + stimulates uterus

Mechanism logic

• Binds PGE₂ receptors in cervix & myometrium
• ↑ Collagen breakdown in cervix → softening + effacement
• ↑ Intracellular Ca²⁺ in myometrium → uterine contractions

Clinical use

• Cervical ripening before induction of labour
• Induction of labour in unfavourable cervix (low Bishop score)

Key effects

• Cervix becomes soft, dilated, effaced
• Uterine contractions begin

Exam traps

• ❌ Not an oxytocin
• ❌ Acts mainly on cervix first, contractions second
• ⚠️ Risk: uterine hyperstimulation, fetal distress

3. Clomiphene Citrate

Core action

• Ovulation induction via estrogen receptor blockade

Mechanism logic

• Blocks estrogen receptors in hypothalamus
• Brain senses low estrogen
• ↑ GnRH → ↑ FSH & LH
• → Follicular growth + ovulation

Clinical use

• First-line ovulation induction in PCOS
• Unexplained anovulatory infertility

Key effects

• Induces ovulation
• Anti-estrogenic effects on:
• Endometrium
• Cervical mucus

Exam traps

• ❌ Ovulation may occur but implantation may fail
• ⚠️ Multiple pregnancy risk
• ⚠️ Ovarian hyperstimulation (less than gonadotropins)

4. Letrozole

Core action

• Aromatase inhibitor → lowers estrogen synthesis

Mechanism logic

• Inhibits aromatase → ↓ estrogen production
• ↓ estrogen → loss of negative feedback
• ↑ FSH secretion
• → Follicular development + ovulation

Clinical use

• First-line ovulation induction in PCOS (now preferred)
• Breast cancer (postmenopausal)

Key effects

• Better endometrial receptivity than clomiphene
• Lower multiple pregnancy rate

Exam traps

• ❌ Does NOT block estrogen receptors
• ✔️ Acts by reducing estrogen synthesis
• ✔️ Shorter half-life → less anti-estrogenic effect

5. Solifenacin

Core action

• Antimuscarinic (M₃ selective) → bladder relaxation

Mechanism logic

• Blocks M₃ receptors in detrusor muscle
• ↓ parasympathetic-mediated contraction
• ↑ bladder capacity

Clinical use

• Overactive bladder
• Urgency
• Frequency
• Urge incontinence

Key effects

• Reduces involuntary detrusor contractions

Exam traps

• ❌ Not for stress incontinence
• ⚠️ Anticholinergic side effects:
• Dry mouth
• Constipation
• Blurred vision
• ⚠️ Avoid in urinary retention, glaucoma

One-line exam memory hooks

• Dinoprostone → “Prepare cervix first, uterus next”
• Tibolone → “3-in-1 postmenopausal steroid”
• Clomiphene → “Trick brain → ↑ FSH/LH”
• Letrozole → “Kill estrogen production”
• Solifenacin → “Calm the bladder”