Owner
U
UntitledVerification
Tags
Tranexamic Acid (TXA)
Core Logic (Why it works)
- Bleeding continues when clots are broken down too fast
- Tranexamic acid prevents clot breakdown
- So → blood loss reduces without affecting ovulation or hormones
Mechanism of Action
- Synthetic lysine analogue
- Competitively inhibits plasminogen → plasmin conversion
- Blocks plasmin binding to fibrin
- Result: stabilizes formed clots (antifibrinolytic)
Pharmacological Effect
- ↓ fibrinolysis
- ↓ menstrual blood loss by 40–60%
- No effect on coagulation cascade initiation
- No effect on ovulation or endometrium growth
Clinical Uses
- Menorrhagia / Heavy menstrual bleeding
- Acute bleeding (trauma, surgery, dental)
- Post-partum hemorrhage (adjunct)
- Epistaxis, hematuria (selected cases)
Dose (Gynecologic use – exam safe)
- 1 g orally 3–4 times daily
- Given only during menstruation
- Usually for up to 5 days
Adverse Effects
- Nausea, vomiting, diarrhea
- Dizziness
- Rare: visual disturbances
- Thromboembolism (rare but exam-important)
Contraindications
- Active thromboembolic disease
- History of DVT / PE
- Subarachnoid hemorrhage
- Severe renal impairment (dose adjust)
Drug Interactions
Combined oral contraceptives → ↑ thrombosis risk
- Other pro-coagulant states
Exam Logic Lock
- Heavy bleeding + normal hormones → Tranexamic acid
- Bleeding problem, not ovulatory problem
- Works during bleeding, not preventive
Mefenamic Acid
Core Logic (Why it works)
- Menstrual bleeding + pain is driven by excess prostaglandins
- Prostaglandins cause:
- Vasodilation
- Uterine contractions
- Block prostaglandins → less pain + less bleeding
Mechanism of Action
- NSAID
- Inhibits COX-1 and COX-2
- ↓ Prostaglandin synthesis in endometrium
Pharmacological Effect
- ↓ uterine contractility
- ↓ endometrial vasodilation
- ↓ menstrual blood loss by 20–30%
- Analgesic + anti-inflammatory
Clinical Uses
- Primary dysmenorrhea
- Mild–moderate menorrhagia
- Pelvic pain associated with menses
Dose
- 500 mg initially
- Then 250–500 mg every 6–8 hours
- Start at onset of menstruation
- Short-term use only
Adverse Effects
- Gastritis
- Peptic ulcer
- Nausea
- Renal impairment (NSAID class)
- Platelet inhibition (mild)
Contraindications
- Peptic ulcer disease
- Chronic kidney disease
- NSAID hypersensitivity
- Bleeding disorders (relative)
Drug Interactions
- Anticoagulants → ↑ bleeding risk
- Other NSAIDs
- Steroids → ↑ GI bleed
Exam Logic Lock
- Pain + bleeding → NSAID
- Best when dysmenorrhea is prominent
- Less effective than TXA for pure bleeding
Norethisterone
Core Logic (Why it works)
- Irregular/heavy bleeding often due to unopposed estrogen
- Estrogen thickens endometrium → unstable shedding
- Progestin:
- Stabilizes endometrium
- Converts it to secretory phase
- Controls timing of bleeding
Mechanism of Action
- Synthetic progestogen
- Suppresses endometrial proliferation
- Induces secretory transformation
- At higher doses:
- Suppresses LH/FSH
- Inhibits ovulation
Pharmacological Effect
- ↓ endometrial thickness
- ↓ bleeding
- Cycle control
- Can delay menstruation
Clinical Uses
- Dysfunctional uterine bleeding
- Anovulatory cycles
- Endometriosis
- Postpone menstruation
- Luteal phase support (selected cases)
Dose (exam standard patterns)
- DUB: 5 mg 2–3 times daily
- Given for 10–21 days
- Withdrawal bleeding occurs after stopping
Adverse Effects
- Weight gain
- Acne
- Mood changes
- Breast tenderness
- Breakthrough bleeding
- Androgenic effects (dose-dependent)
Contraindications
- Pregnancy
- Active liver disease
- Breast cancer
- Thromboembolic disorders
- Undiagnosed vaginal bleeding
Drug Interactions
- Enzyme inducers (rifampicin, phenytoin) ↓ effect
- Combined hormonal therapies
Exam Logic Lock
- Irregular cycles / anovulation → Progestin
- Endometrial problem, not clot or prostaglandin problem
- Used to regulate, not for acute bleeding only
One-Look Comparison (High-Yield)
Feature | Tranexamic Acid | Mefenamic Acid | Norethisterone |
Primary action | Antifibrinolytic | COX inhibition | Progestin |
Targets | Clot breakdown | Prostaglandins | Endometrium |
Best for | Pure heavy bleeding | Pain + bleeding | Irregular / anovulatory |
Hormonal effect | None | None | Yes |
Ovulation effect | No | No | Yes (high dose) |
Final Exam Reflex Line
- Heavy bleeding only → Tranexamic acid
- Pain + bleeding → Mefenamic acid
- Irregular cycles / DUB → Norethisterone
Abnormal Uterine Bleeding – Drug Comparison (Exam Gold Table)
Feature | Tranexamic Acid (TXA) | Mefenamic Acid | Norethisterone |
Drug class | Antifibrinolytic | NSAID | Progestin |
Core problem addressed | Excess clot breakdown | Excess prostaglandins | Endometrial instability (unopposed estrogen / anovulation) |
Primary target | Plasminogen / plasmin | COX-1 & COX-2 | Endometrium ± HPO axis |
Mechanism | Blocks plasminogen → plasmin conversion → stabilizes fibrin clot | ↓ Prostaglandin synthesis | Converts proliferative → secretory endometrium |
Effect on fibrinolysis | ↓↓↓ (major effect) | No | No |
Effect on prostaglandins | No | ↓↓↓ | Indirect ↓ |
Effect on endometrium | None | Minimal | Direct stabilization |
Effect on ovulation | ❌ No | ❌ No | ✅ Yes (at high dose) |
Hormonal effect | None | None | Present |
Reduction in menstrual blood loss | 40–60% | 20–30% | Variable |
Effect on dysmenorrhea | ❌ No | ✅ Yes (best) | Mild |
Timing of use | Only during menstruation | From onset of menses | Given for days–weeks |
Typical exam dose | 1 g PO 3–4×/day × ≤5 days | 500 mg stat → 250–500 mg 6–8-hourly | 5 mg 2–3×/day for 10–21 days |
Best indication | Pure heavy bleeding with normal cycles | Pain + bleeding | Irregular / anovulatory bleeding (DUB) |
Role in cycle control | ❌ None | ❌ None | ✅ Yes |
Use to delay menses | ❌ No | ❌ No | ✅ Yes |
Common adverse effects | Nausea, dizziness | Gastritis, renal effects | Weight gain, acne, mood change |
Major exam-important risk | Thromboembolism (rare) | GI bleed | Thrombosis, androgenic effects |
Key contraindication | DVT / PE, active thrombosis | Peptic ulcer, CKD | Pregnancy, breast CA, liver disease |
Key drug interaction | COCs ↑ thrombosis risk | Anticoagulants ↑ bleed | Enzyme inducers ↓ effect |
Ultra-Short Exam Reflex (1-line memory)
- Bleeding only → Tranexamic acid
- Pain + bleeding → Mefenamic acid
- Irregular / anovulatory bleeding → Norethisterone