stumpy Posted March 22, 2007 Report Share Posted March 22, 2007 Hi, does anyone have any information on the effects of metronidazole and the combined contraceptive pill. My girlfriend who is on the pill was prescribed these and we used condoms in addition to the pill for the week she was on the antibiotics but not the week after although we did have sex. I read the chances of a pregnancy because of this is low but would appreciate a view from anyone in the know as to how low the chance is. Also, we will do a pregnancy test but as she is on the combined pill when will know all is clear? She comes of the pill for 7 days next Tuesday and should bleed by Thursdsay but as this is a withdrawel bleed can we use this as the date to do the test on and be confident in the result? Many thanks. Link to comment Share on other sites More sharing options...
pe7e Posted March 22, 2007 Report Share Posted March 22, 2007 There's no apparant contra indicators regarding this drug and birth control medications, more info Here Link to comment Share on other sites More sharing options...
elef Posted March 22, 2007 Report Share Posted March 22, 2007 True, but antibiotics has an effect on the stomach and may result in that the hormone level will be lower with an unexpected pregnancy as result. A comment from one of our board docs maybe? Link to comment Share on other sites More sharing options...
stumpy Posted March 22, 2007 Author Report Share Posted March 22, 2007 Thanks, would also appreciate a take from a doc if possible. Link to comment Share on other sites More sharing options...
tomc12 Posted March 22, 2007 Report Share Posted March 22, 2007 Metronidazole should not reduce the effectiveness of birth control pills per se. However metronidazole frequently causes nausea/vomiting if taken on an empty stomach. If she took metronidazole shortly after taking her BCP and the metronidazole caused vomiting, then the effectiveness of the BCP could be reduced. If that didn't happen, then not a problem. Link to comment Share on other sites More sharing options...
tomc12 Posted March 22, 2007 Report Share Posted March 22, 2007 Sorry, missed the last part of your question. Home pregnancy tests are generally positive 14 days after the egg is fertilized. Link to comment Share on other sites More sharing options...
stumpy Posted March 23, 2007 Author Report Share Posted March 23, 2007 Thanks very much for the reply. When can we do the home pregnancy test and regard the result as definative? Home kits claim to be able to detect up to 4 days before period due. However, as she is on the combined pill she does not have a 'true' period, only a withdraw bleed when she has 7 days off. Can we regard the day she bleeds as the day to test? Thanks. Link to comment Share on other sites More sharing options...
tomc12 Posted March 23, 2007 Report Share Posted March 23, 2007 No, you can not regard the day she bleeds to do the test as she is on BCP's. Anytime she is late taking her pill, she could start bleeding. If she may have vomited up a BCP, then you go by the standard rule-BCP's are effective once they have been taken for 7 days. So run the test 21 days after she vomited her BCP. Some of the supersensitive pregnancy tests can become positive 8 days after fertilization, but the keyword is can. All home pregnancy tests should reliably show a positive response 14 days after fertilization. If she did not throw up any pills, then metronidazole does not reduce the effectiveness of BCP's. Link to comment Share on other sites More sharing options...
stumpy Posted March 23, 2007 Author Report Share Posted March 23, 2007 Thanks again for the reply Tom. She did not throw up any pills (pill is yasmin BTW) and I was concerned by the generic warning on the packet that antibiotics can stop the pill working but I note your comments that metronidazole does not reduce the efficiency of the pill. Appreciate your help. Link to comment Share on other sites More sharing options...
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