CKS is no longer commissioned by the National Institute for Health and Clinical Excellence (NICE). NICE remains committed to providing a replacement service for CKS and is currently reviewing its options. In the meantime, although CKS content is now not being maintained, it still remains relevant and will continue to be made available. CKS content was generated under a programme of topic creation and update. To check if the topic you are viewing is current or out of date, please refer to the topic publication details by clicking on the 'How up-to-date is this topic?' link in the left hand menu on individual topic pages.
Contraception - emergency - Management
When might a contraceptive method fail?
Table 1 lists the situations in which contraception is not reliable. Note that there is some controversy about the recommendations for missed combined oral contraceptive pills, and that some of the details differ from information given in the summary of product characteristics leaflets that manufacturers provide with their products.
Table 1. Situations in which contraceptive methods may fail.
Contraceptive method | When contraception is not reliable |
|---|
Combined hormonal contraception, progestogen only pills and implants — progestogen only injectables, and the levonorgestrel intrauterine system are not affected | If a liver enzyme–inducing drug is taken: until 28 days after stopping the liver enzyme–inducing drug [FFPRHC, 2006b]. Liver enzyme-inducing drugs include rifampicin, rifabutin, barbiturates, bosentan, carbamazepine, oxcarbazepine, phenytoin, ritonavir (and possibly other antivirals), griseofulvin, topiramate, and St John's wort. For more information, see the CKS topic on Contraception. |
Combined oral contraceptive pills containing 30–35 micrograms of ethinyl estradiol | If >= 3 pills are missed: until active pills have been taken for at least 7 days in a row [FFPRHC, 2005a]. The most risky times to miss combined oral contraceptive pills are the week before or after the inactive pill (or pill-free) interval. |
Combined oral contraceptive pills containing 20 micrograms of ethinyl estradiol | If >= 2 pills are missed: until active pills have been taken for at least 7 days in a row [FFPRHC, 2005a]. The most risky times to miss combined oral contraceptive pills are the week before or after the inactive pill (or pill-free) interval. |
Progestogen-only pill | If the pill is taken late: until 48 hours after resuming oral contraception [FFPRHC, 2005a]. With one exception, for all progestogen only pills, 'late' means > 3 hours late; the exception is desogestrel (Cerazette ®), in which case 'late' means > 12 hours late [ABPI Medicines Compendium, 2004c]. The risk of contraceptive failure is low if the woman is breastfeeding and amenorrhoeic. |
Transdermal combination contraceptive patch | If the patch lifts (completely or partially) for longer than 48 hours, or there is a delay of more than 48 hours in changing patches at the end of week 1 or 2, or if there is a delay of more than 48 hours in starting a new patch after the patch-free week, or starting a new cycle: until 7 days after starting a new cycle [ABPI Medicines Compendium, 2007; FPA, 2009]. |
Parenteral progestogen (medroxyprogesterone acetate) | The manufacturer is more cautious than the World Health Organization and regards contraception as unreliable when an injection is >= 5 days late (i.e. > 12 weeks and 5 days after the last injection) [ABPI Medicines Compendium, 2004d]. |
Copper intrauterine device or levonorgestrel intrauterine system | Expulsion, or removal of the device without alternative contraception [FFPRHC, 2006b]. |
Condoms, male or female | If the condom splits or dislodges during intercourse [FFPRHC, 2007]. |
Diaphragm or cap | If the diaphragm or cap is inserted incorrectly, is torn/dislodged during intercourse, is used without spermicide, or is removed too early (i.e. < 6 hours after intercourse) [FFPRHC, 2006b]. |
© NHS Institute for Innovation and Improvement