The pill and antibiotics

Both Rifampin and Rifabutin are what are known as ‘enzyme-inducing’ medicines. This means they increase the level of certain enzymes in the body to increase the speed at which they work. This increased enzyme level affects the hormones in the pill that prevents pregnancy. As these hormones are broken down faster before they get a chance to work properly, it makes them less effective than advertised.  

If you rely on the pill as a contraception method and you’ve been prescribed either of these antibiotics to treat an illness, then you’ll need to look into using additional types of contraception during this time. You can keep taking the pill as per usual to keep your cycle regular, but using condoms or a diaphragm until you come off the antibiotic will ensure the chances of pregnancy is low. 

There are other types of hormonal contraceptives which are also rendered less effective by taking Rifampin and Rifabutin antibiotics. These are: 

• The vaginal ring
• The contraceptive patch
• The combined pill (progestin and oestrogen)
• The mini pill (progestin only)
• The contraceptive implant 

This also means that these forms of hormonal contraceptives are not a suitable alternative contraception method when taking Rifampin and Rifabutin. 

The following methods of contraception are not affected by these antibiotics:

• IUD (copper coil)
• IUS (hormonal coil)
• Contraceptive injection 
• Condoms (male and female condoms)
• Diaphragm

These forms of contraception are suitable as an alternative or additional contraceptive method to protect against pregnancy while taking Rifampin or Rifabutin.

If you’re taking any other antibiotic that isn’t Rifampin or Rifabutin, it will not interfere with the contraceptive pill and its effectiveness. Common types of antibiotics include: 

• Amoxicillin
• Doxycycline
• Cephalexin
• Metronidazole 
• Clindamycin
• Ciprofloxacin
• Azithromycin

However, taking antibiotics can cause vomiting or an upset stomach. If this happens, you may not be protected against pregnancy if you’re on the pill. In this situation, you should use condoms until the symptoms resolve, and you start feeling better for seven days.