For maximal protection, additional non-hormonal contraception should be recommended for the duration of antibiotic therapy and for seven days afterwards. Those on long term antibiotic therapy need only take extra precautions for the first two weeks of antibiotic therapy. Spotting and breakthrough bleeding are possible signs of diminished contraceptive effectiveness. The efficacy of the contraceptive pill may be decreased when it is administered concomitantly with other medicines such as the anti-epileptic agents, rifampicin, phenylbutazone and ampicillin. With vomiting or diarrhoea, the absorption of oral contraceptives may be diminished and women should be advised to use additional methods of contraception at the time of such disorders.
Surgery is more likely to be associated with an increased incidence of thrombotic side-effects.
Adequate precaution should be taken. Under no circumstances should the oral contraceptive tablet be stopped without having adopted a satisfactory alternative method of contraception. It will do this as long as you follow the schedule carefully. If you miss taking one tablet, take it the next morning or as soon as possible, then take the next tablet at the usual time and continue the course as before. Remember to use an additional contraceptive method until you finish the package.