Published: March 1999


Avoiding Pregnancy Risk When Changing Oral Contraceptives

Prescriber Update 15, August 1997
March 1999

Medsafe Editorial Team

When changing brands of oral contraceptive tablets, counsel women to start the new brand on active hormone tablets and skip the pill free interval or use non-hormonal forms of contraception until 7 active tablets of the new brand have been taken. Either option will ensure uninterrupted contraceptive cover.

Following recent publicity about the risks of combined oral contraceptives (OCs) and venous thromboembolism, it is likely that a number of women will change brands. When changing brands of OCs it is important that the pill-free interval is not prolonged. Increasing this interval by as little as one day, is associated with an increased risk of breakthrough ovulation and pregnancy.

Advise women to follow one of the following procedures when changing brands:

Start the new brand on active hormone pills and skip the pill-free interval (i.e. follow active tablets of the former brand with active tablets of the new brand without a pill-free interval). Following this advice means that the woman will miss a withdrawal bleed for that cycle (advice given by the Family Planning Association).
Apply the 7 day rule and use alternative methods of contraception, such as condoms and a spermicide (which should be prescribed during the consultation), until such time as 7 active hormone tablets have been taken from the new pack.


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