Antibiotics: do they affect contraceptives?

Aug 23 2012

NPS MedicineWise has released information for consumers about taking antibiotics when also using hormonal contraceptives, explaining that there are only two antibiotics that affect how hormonal contraceptives work.

There are many misconceptions regarding the impact of antibiotics in our bodies, says NPS MedicineWise clinical adviser Dr Philippa Binns.

“While it’s important to always be careful with medicines to avoid mishaps, it’s also wise to separate the fact from fiction,” she says.

“Not all antibiotics interfere with how well hormonal contraceptives work. However there are exceptions, so it’s important for women to always check whether their antibiotic may have an impact.”

Women using hormonal contraception are encouraged to get advice from their doctor or pharmacist so they’re reassured about the need to take precautions if prescribed an antibiotic.

“Many women who use hormonal contraceptive methods often express concern that antibiotics may jeopardise their effectiveness,” says Dr Binns.

“In fact, there are only two antibiotics which are thought to affect how well some hormonal contraceptives work.”

These are rifampicin – sold under the brand names Rifadin and Rimycin – and rifabutin – sold as Mycobutin.  These antibiotics are usually only used to treat certain bacterial infections that are serious such as tuberculosis and methicillin-resistant Staphylococcus aureus (MRSA), and for preventing meningitis (an infection around the brain or spinal cord) so most people won’t be prescribed them.

However if women are prescribed rifampicin or rifabutin and they’re using a hormonal contraceptive pill, under-skin implant or vaginal ring, they’ll need to use extra contraceptive precautions (such as condoms) while taking these antibiotics, and potentially for a few days after finishing the course.

The information from NPS MedicineWise is in line with new advice released in the third edition of Family Planning’s contraceptive handbook in June 2012.

When it comes to taking antibiotics generally, Dr Binns recommends talking to your doctor or pharmacist if you have a stomach upset while you’re on a medicine.

“Persistent vomiting or severe diarrhoea, say for more than 24 hours, may reduce the effectiveness of a hormonal contraceptive pill and so you may need to use another contraceptive method.”

Dr Binns also reminds anyone prescribed antibiotics that they can still be antibiotic resistance fighters by following the directions given by their doctor.

“We know that using antibiotics when they’re not needed, such as for viral infections like colds and flu, is contributing to global antibiotic resistance,” she says.

“But you can also help fight resistance when you do need antibiotics by taking them at the right time, at the dose prescribed, and for as long as directed.

“And don’t share antibiotics or keep them for another time as this can also lead to antibiotic resistance. Return any leftover pills to your pharmacy for disposal.”

For more information on antibiotics and contraception, visit http://www.nps.org.au/medicines/antibiotics_for_respiratory_tract_infections/how_do_i_take_my_antibiotics/antibiotics_and_contraceptives