Is the effectiveness of levonorgestrel (LN) 1.5mg alone the same as the combination of levonorgestrel (LN) 1.5mg with Ethinyl estradiol (EE) 30mg for emergency contraception?

Levonorgestrel 1.5mg Alone vs. Combined with Ethinyl Estradiol for Emergency Contraception

Levonorgestrel 1.5mg alone is the recommended emergency contraception regimen, NOT the combination with ethinyl estradiol 30mg, as the combined estrogen-progestin regimen is the least effective emergency contraception option available. 1

Effectiveness Hierarchy

The evidence clearly establishes a hierarchy of emergency contraception effectiveness:

• Copper IUD is most effective (failure rate <1%), followed by ulipristal acetate, then levonorgestrel alone, with combined estrogen-progestin regimens being the least effective option 1
• Levonorgestrel 1.5mg as a single dose is the standard recommended regimen by the American Academy of Pediatrics and American College of Obstetricians and Gynecologists 2
• The combined regimen (levonorgestrel with ethinyl estradiol) is explicitly not recommended due to significantly reduced effectiveness compared to levonorgestrel alone 3

Standard Dosing Recommendations

• Give levonorgestrel 1.5mg as a single dose (or two 0.75mg pills taken together) as soon as possible within 72 hours of unprotected intercourse 2
• This single-dose regimen is both safe and effective, with pregnancy rates as low as 0.7% in clinical studies 4
• The mechanism works primarily by delaying or inhibiting ovulation, and is most effective when taken before ovulation occurs 5

Critical Timing Considerations

• Levonorgestrel effectiveness decreases significantly after 72 hours, with pregnancy rates increasing at 4-5 days post-intercourse 2
• When taken immediately after sex, levonorgestrel could potentially reduce pregnancy risk by 91%, but real-world effectiveness ranges from 49-67% due to treatment delays 6
• If the patient presents beyond 72 hours (3-5 days post-intercourse), ulipristal acetate 30mg is significantly more effective than levonorgestrel, with 65% lower pregnancy risk and maintained effectiveness throughout the full 120-hour window 2

Special Population Considerations

• For women weighing >165 pounds, ulipristal acetate is more effective than levonorgestrel regardless of timing 2
• Levonorgestrel may be less effective in obese women regardless of dose, and the mechanism of action has biological limits that cannot be overcome by simply increasing the dose 2

Post-Administration Instructions

• Resume or start regular contraception immediately after levonorgestrel use, but use a barrier method or abstain for 7 consecutive days 3
• If already on combined oral contraceptives, continue the COC as scheduled after emergency contraception use 3
• A pregnancy test is recommended if withdrawal bleeding does not occur within 3 weeks 1

Common Pitfalls to Avoid

• Do not use the combined estrogen-progestin regimen (levonorgestrel + ethinyl estradiol) as it is the least effective emergency contraception option 1
• Do not delay administration—effectiveness decreases with time for all oral methods 2
• Do not assume higher doses of levonorgestrel will improve effectiveness in obese women; instead, consider ulipristal acetate or copper IUD 2
• Menstrual disturbances (early/late menses, intermenstrual bleeding) occur in approximately 43% of users but are generally well-tolerated 4