What is 15-methyl PGF2α?
15-methyl PGF2α (carboprost tromethamine) is a synthetic prostaglandin analogue used primarily as an oxytocic agent for treating postpartum hemorrhage due to uterine atony and for inducing abortion in the second trimester. 1
Chemical Structure and Formulation
- 15-methyl PGF2α is the (15S)-15 methyl analogue of naturally occurring prostaglandin F2α, formulated as the tromethamine salt (carboprost tromethamine) 1
- Each mL contains carboprost tromethamine equivalent to 250 mcg of carboprost, supplied as a sterile solution for intramuscular injection 1
- The molecular formula is C21H36O5.C4H11NO3 with a molecular weight of 489.64 1
Important Nomenclature Distinction
- Do not confuse 15-methyl PGF2α (carboprost) with 11β-PGF2α, which is a metabolite of PGD2 used as a diagnostic marker for mast cell activation syndrome, not a therapeutic agent 2
- The nomenclature is confusing: 9α,11α-PGF2 (PGF2α) is a metabolite of PGE2 or PGH2, while 9α,11β-PGF2 (11β-PGF2α) is a metabolite of PGD2—both are distinct from therapeutic 15-methyl PGF2α 2
Primary Clinical Indications
Postpartum Hemorrhage
- 15-methyl PGF2α is indicated for intractable atonic postpartum hemorrhage when conventional uterotonic agents fail 3
- Administered intramuscularly at 250 mcg doses, with mean effective dose of 437.5 mcg (1.75 injections) 3
- In one series, 15 of 16 patients with severe atonic hemorrhage responded satisfactorily, avoiding hysterectomy 3
- Intracervical administration may be the most efficient route, with good effect achievable even with a single 250 mcg dose 4
- The lack of response (5.88% failure rate) typically indicates alternative pathology requiring laparotomy 4
Pregnancy Termination
- Used for therapeutic termination of pregnancy and management of intrauterine fetal death during the second and third trimesters 5
- Mean abortion induction time is 7.3 hours for intrauterine fetal death and 12.6 hours for therapeutic termination 5
- Success rate of 90 out of 92 patients (97.8%) when administered intramuscularly 5
Mechanism of Action
- Acts as an oxytocic by stimulating myometrial contractions through prostaglandin receptor activation 1
- Unlike naturally occurring PGF2α, the 15-methyl modification provides resistance to enzymatic degradation, prolonging its duration of action 1
Administration Routes
- Intramuscular (standard): Deep muscular injection of 250-500 mcg doses 4, 3
- Intracervical: May offer superior efficacy for postpartum hemorrhage 4
- Intramyometrial: Alternative route for direct uterine administration 4
Common Side Effects
- Gastrointestinal symptoms (vomiting and diarrhea) are frequent 6
- Fever and rigors occur commonly 7
- Pain at injection site and uterine cramping 7
- Temperature changes, including significant decreases in body temperature 6
Safety Considerations
- High embryolethality: Demonstrates significant embryotoxicity regardless of timing during pregnancy 8
- Rabbits are more sensitive than rats to embryotoxic effects 8
- Skeletal anomalies (primarily ribs and thoracic vertebrae) observed in rat fetuses at doses of 0.05-0.25 mg/kg 8
- The single case requiring hysterectomy despite treatment involved severe intrauterine infection 3
Practical Clinical Recommendations
- Every obstetric clinic should maintain 3 ampules (750 mcg total) of carboprost available for emergency postpartum hemorrhage management 4
- Administer after conventional methods and manipulations have failed 4
- Risk factors associated with need include preeclampsia, prolonged labor, general anesthesia, and high multiparity 4