Pregnancy termination with a high and medium dosage regimen of RU 486

Area of Science:

• Reproductive Endocrinology
• Pharmacology
• Medical Abortion

Background:

• RU 486 (mifepristone) is a synthetic progesterone receptor blocker used in medical abortion.
• Optimizing RU 486 dosage and duration is crucial for efficacy and safety.

Purpose of the Study:

• To compare the efficacy and side effect profiles of different RU 486 dose regimens for early pregnancy termination.
• To assess the antiglucocorticoid effects of RU 486 by measuring serum cortisol levels.

Main Methods:

• Healthy pregnant women (≤49 days gestation) received one of three RU 486 regimens.
• Regimens included high-dose/short-duration (400 mg/day x 4 days or 200 mg/day x 4 days) and medium-dose/longer-duration (100 mg/day x 7 days).
• Serum cortisol levels were monitored to evaluate antiglucocorticoid effects.

Main Results:

• High-dose/short-duration regimens had >80% side effects and only 10% success rate.
• Medium-dose/longer-duration regimen showed 40-60% side effects and a 72.3% success rate.
• AM cortisol levels were elevated in all groups, highest with high-dose RU 486, normalizing post-treatment.

Conclusions:

• A medium dose of RU 486 administered over a longer duration (100 mg/day x 7 days) is more effective and better tolerated than higher doses over shorter periods.
• Predictive factors for successful medical abortion with RU 486 were not identified.
• The reasons for treatment failure in 30% of subjects on the medium-dose regimen require further investigation.