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Bear, DE
A 19-year-old female asked:

Does isoniazid lower the effectiveness of hormonal birth control?

3 doctor answers4 doctors weighed in
Dr. William Belk
Specializes in Family Medicine
No: Antibiotics do not decrease the effectiveness of BCP's
Dr. Kristel Hunt
Hepatology 23 years experience
Yes it can: another form of birth control is typically recommended while on INH (condoms, barrier methods). if you're sexually active, would discuss with your doc as to the best methods.
Dr. Jeffrey Levine
Family Medicine 31 years experience
Isoniazid (INH) does NOT reduce the effectiveness of hormonal contraceptives. Since it decreases the ability of your body (Cytochome P450 system) to metabolize hormonal contraceptives, it theoretically can increase their effectiveness. However, another antibiotic used to treat Tuberculosis (TB) - Rifampin - accelerates body's metabolism of hormonal contraceptives, decreasing their effectiveness.
Aug 1, 2014
Dr. Kristel Hunt
Hepatology 23 years experience
Provided original answer
Ok I stand corrected - does indeed inhibit p450. Curious though, why do all major site recommend those barrier methods? lumping all anti-TB meds together I guess? appreciate the comment.
Aug 1, 2014
Dr. Laura Yauch
Specializes in Family Medicine
No: According to the National Institute of Health Rifampin / rifibutin is the only antibiotic that has been clearly shown to make hormonal birth control less effective.
Dr. Kristel Hunt
Hepatology 23 years experience
CDC says "Women who use any form of hormonal birth control should be advised to add, or switch to, a barrier method." http://www.cdc.gov/mmwr/preview/mmwrhtml/mm6048a3.htm but it seems there's enough controversy regarding this - stay safe and discuss with your own doctor!!
Aug 1, 2014

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