What is the recommended dose of emergency contraception for a patient with a weight exceeding 100kg?

Emergency Contraception Dosing for Patients Weighing Over 100kg

For patients weighing more than 100kg, ulipristal acetate (30mg) is recommended over levonorgestrel as emergency contraception due to decreased effectiveness of levonorgestrel in heavier individuals. 1

Effectiveness of Emergency Contraception Options by Weight

Levonorgestrel (Plan B One-Step and generics)

• Standard dose: 1.5mg as a single dose
• Effectiveness decreases significantly in women who weigh more than 165 pounds (75kg)
• Considered ineffective in women who weigh more than 176 pounds (80kg) 1
• Given that the patient weighs over 100kg, levonorgestrel would have substantially reduced efficacy

Ulipristal Acetate

• Standard dose: 30mg as a single dose
• Maintains greater effectiveness than levonorgestrel in heavier women 1
• More effective than levonorgestrel at the end of the 5-day window of use 1

Copper IUD

• Most effective emergency contraception option regardless of weight
• Can be inserted within 5 days of unprotected intercourse
• Effectiveness approaching 99% 1
• Can be continued as regular contraception

Decision Algorithm for Emergency Contraception in Patients >100kg

1. First choice: Copper IUD insertion (if acceptable to patient and no contraindications)

   • Highest effectiveness regardless of weight
   • Provides ongoing contraception

2. Second choice: Ulipristal acetate 30mg as a single dose

   • More effective than levonorgestrel in heavier women
   • Should be taken as soon as possible within 5 days of unprotected intercourse

3. Third choice (if other options unavailable): Levonorgestrel 1.5mg as a single dose

   • Recognize that effectiveness is significantly reduced at weights >100kg
   • Consider doubling the dose (off-label) if this is the only available option

Important Clinical Considerations

• Timing is critical: All emergency contraception methods are more effective the sooner they are used after unprotected intercourse 1
• Advance provision of emergency contraception should be considered for patients at higher weights to ensure timely access 1
• A pregnancy test is not necessary before prescribing levonorgestrel EC, as it has no teratogenic effects 1
• Ulipristal acetate is pregnancy category X, so pregnancy should be ruled out before use 1
• Regular contraception should be initiated or continued after emergency contraception use

Common Pitfalls to Avoid

• Assuming standard levonorgestrel dosing is equally effective for all body weights
• Delaying emergency contraception administration (efficacy decreases with time)
• Failing to consider the copper IUD as an emergency contraception option
• Not providing counseling on ongoing contraception after emergency contraception use

By prioritizing either ulipristal acetate or copper IUD insertion for patients weighing over 100kg, healthcare providers can help ensure more effective pregnancy prevention after unprotected intercourse.