The emergency contraceptive drug, levonorgestrel: A review of post-coital oral and peri-coital vaginal administration for prevention of pregnancy

Abstract

The objective of our study was the evaluation and elucidation of levonorgestrel (LNG) as emergency contraception (EC) administered through oral and vaginal routes. Data regarding post-coital oral and peri-coital vaginal application of LNG were extracted from the literature through MEDLINE database service for years 2001–2010. It was found that a single dose of 1.5 mg LNG or two doses of 0.75 mg LNG 12 h apart were used for EC. Currently, LNG is also on trial for vaginal application as EC in Carraguard gel for ‘dual protection’. The oral or vaginal dose of 1.5 mg LNG resulted in peak plasma concentration, C_max 19.2 or 3.21 ng/ml, with shorter time, T_max 1.4 or 6.6 h, and greater AUC, 152.7 or 52.5 ng.h/ml, with shorter half-life, 25 or 32 h, respectively. LNG EC inhibited mid-cycle LH surge and delayed or prevented ovulation when administered before ovulation. Mechanism of action of LNG EC appeared to inhibit or delay ovulation. The risk of pregnancy was 4.12%. A single dose of 1.5 mg LNG could reduce the pregnancy rate to 0.7%. Occurrence of ectopic pregnancy following failure of LNG EC was reported. This EC caused no serious adverse effects but was associated with menstrual disturbance. Although widely acceptable, the cost and short-supply to rural areas pose a barrier to access EC for the poor and rural-dwellers, respectively. It was concluded that unlike post-coital oral administration, peri-coital vaginal application of 1.5 mg LNG needs further study to be an alternative option for women to use it for prevention of pregnancy.

Keywords::

• Hormonal emergency contraception
• mechanism of action
• peri-coital vaginal contraception
• pharmacokinetics
• post-coital oral contraception
• vaginal gel

Declaration of interest: The author reports no conflicts of interest. The author alone is responsible for the content and writing of the paper.