The Faculty of Family Planning of the Royal College of Obstetricians and Gynecologists advise:
"additional contraceptive precautions should be taken whilst taking a short course of a broad spectrum antibiotic and for 7 days after stopping. If these 7 days run beyond the end of a packet, the next packet should be started immediately without a break."
PENICILLIN, AMOXICILLIN, METRONIDAZOLE
(FLAGYL), ERYTHROMYCIN and CLINDAMYCIN.
If you are in any doubt as to the type of contraceptive pill you are taking and its effect with these antibiotics, please inform and consult your G.P.