Morning After Pill

Levonorgestrel (marketed in Australia under the brand names NorLevo-1, NorLevo, Postinor and Levonelle), taken as a 1.5 mg tablet or two 0.75 mg tablets, is used as an oral emergency contraceptive within 72 hours of unprotected sexual intercourse.

Product information on Postinor describes Levonorgestrel as a white or almost white, odourless or almost odourless, crystalline powder. Each white tablet contains 1.5 milligrams of levonorgestrel and the following excipients: starch – potato; starch – maize; silica – colloidal anhydrous; magnesium stearate; talc; lactose.

The way Postinor works in unknown. The product information notes ‘the precise mode of action of Postinor-1 is not known.

Emergency hormonal contraception is thought to work mainly by preventing ovulation and fertilisation by altering tubal transport of sperm and/or ova.

It may also cause endometrial [lining of the uterus] changes that discourage implantation. Levonorgestrel is not effective once the process of implantation [once a fertilised egg attaches to the wall of the uterus] has begun’.

Postinor has been shown to have some effectiveness in preventing a pregnancy after unprotected sex.

From earlier studies where two Postinor-2 tablets (each 750 micrograms) have been taken 12 hours apart, it has been estimated that Postinor-2 prevents 85% of expected pregnancies.

Efficacy appears to decline with time after intercourse (95% within 24 hours, 85% 24-48 hours, 58% if used between 48 and 72 hours). In an additional study to compare taking the two tablets 12 hours apart versus taking a total dose of 1.5mg after unprotected intercourse, similar rates of prevention of pregnancy were observed when taken within 72 hours.

You can read the product information here.

Recently, the Therapeutic Goods Administration (the organisation that regulates medications in Australia) has begun reviewing whether the medication is effective for women weighing over 70kg.

However, TGA advises that ‘consumers are advised that, irrespective of the weight of the woman taking it, levonorgestrel may not prevent pregnancy in every case. The sooner you take emergency contraceptive, the more likely it is that it will work’.

You can read this advice from TGA here.