Timeline for Misoprostol Administration in Medical Abortion
Misoprostol should be administered 24-48 hours after mifepristone for medical abortion up to 10 weeks (70 days) gestation, though simultaneous administration is also effective if logistically necessary. 1, 2
Standard Timing Protocol
Optimal Interval: 24-48 Hours
- The evidence-based regimen uses mifepristone 200 mg orally followed by misoprostol 800 mcg (buccal or vaginal) administered 24-48 hours later, with demonstrated efficacy of 97.7% through 63 days gestation 2
- This interval allows for home administration of misoprostol, which has been proven safe and effective in large-scale studies involving over 13,000 women 2
- The 24-48 hour window provides flexibility for patient scheduling while maintaining optimal efficacy 3, 2
Alternative Timing: Simultaneous Administration
- Simultaneous administration (misoprostol given immediately with mifepristone) achieves comparable efficacy of 95.1% versus 96.9% for the 24-hour interval, meeting statistical noninferiority criteria 1
- This approach may be preferred when follow-up compliance is uncertain or when immediate completion is logistically advantageous 1
- The tradeoff is increased side effects: nausea, diarrhea, and chills occur more frequently with simultaneous dosing 1
Route-Specific Considerations
Vaginal Administration
- Efficacy of 93.8% when combined with mifepristone 200 mg at 48-hour interval through 63 days gestation 4
- Lower incidence of fever, chills, and gastrointestinal symptoms compared to sublingual/buccal routes 4
- Preferred by some patients for reduced systemic side effects 4
Buccal Administration
- Efficacy of 95% through 56 days gestation and remains highly effective through 63 days 3, 2
- Comparable patient satisfaction (92%) to vaginal route (95%) 3
- May be preferred by patients who wish to avoid vaginal administration 3
Sublingual Administration
- Efficacy of 98.2% through 63 days gestation 4
- Significantly higher rates of fever, chills, nausea, vomiting, and diarrhea compared to vaginal route 4
- Requires optimization of dosing to balance efficacy against side effects 4
Gestational Age-Specific Efficacy
- Highest efficacy occurs at 29-42 days gestation (98.8%) 2
- Efficacy remains acceptable but decreases slightly at 57-63 days (95.5%) 2
- The odds of requiring aspiration increase with advancing gestational age, though overall rates remain low 2
Critical Safety Parameters
Absolute Contraindications
- Avoid misoprostol in women with previous cesarean delivery due to uterine rupture risk 5
- High-risk patients require management at experienced centers with emergency support services 5
Expected Adverse Effects
- Gastrointestinal symptoms (nausea, vomiting, diarrhea) are common and expected with misoprostol 5
- Median vaginal bleeding duration is 17 days 4
- Serious complications are rare: infection requiring hospitalization (0.01%) and transfusion (0.03%) 2
Common Pitfalls to Avoid
- Do not restrict medical abortion to ≤49 days based on outdated FDA labeling—evidence supports safety and efficacy through 63 days (9 weeks) gestation 2, 6
- Do not routinely require ultrasonography for gestational age confirmation if clinical dating is reliable 6
- Do not delay treatment in high-risk patients who would be better served by surgical evacuation (dilatation and evacuation), which carries lower bleeding risk 5