Levonorgestrel-only dosing strategies for emergency contraception

Area of Science:

• Reproductive Health
• Pharmacology
• Clinical Pharmacy

Background:

• The standard United States Food and Drug Administration (FDA)-approved emergency contraception (EC) regimen is two 0.75 mg doses of levonorgestrel taken 12 hours apart.
• Alternative dosing strategies, including a single 1.5 mg dose or two 0.75 mg doses taken 12-24 hours apart, have been proposed and studied.

Purpose of the Study:

• To evaluate and describe existing pharmacokinetic and patient outcome data for levonorgestrel EC.
• To compare the efficacy and safety of a single 1.5 mg dose versus two 0.75 mg doses of levonorgestrel for emergency contraception.

Main Methods:

• A literature search of MEDLINE and International Pharmaceutical Abstracts (1967-2006) was conducted.
• Additional relevant studies were identified from bibliographies of selected literature.
• Pharmacokinetic and patient outcome data were analyzed.

Main Results:

• All identified studies demonstrated that emergency contraception effectively prevents pregnancy.
• Evidence supports the safety and efficacy of a single 1.5 mg dose of levonorgestrel for EC.
• The second 0.75 mg dose of levonorgestrel can be administered 12-24 hours after the first dose without compromising efficacy.

Conclusions:

• Both single 1.5 mg and two 0.75 mg levonorgestrel dosing regimens are safe and effective for emergency contraception.
• Understanding these dosing strategies is crucial for healthcare providers, particularly pharmacists, involved in dispensing EC.