Drugs which have potential to effect the efficacy of hormonal contraception

Example drugs are listed. Please check guidance (1) and BNF for more comprehensive information.

• drugs that reduce contraceptive hormone levels or decrease contraceptive effects are
  
  
  • antiepileptics e.g. - carbamazepine, phenobarbital, phenytoin
    • modest to marked reduction in ethinylestradiol (EE) and progestogens. Possible reduced contraceptive efficacy
      
      
  • antibiotics e.g. - rifabutin, rifampicin
    • rifabutin associated with a modest reduction in EE or estradiol and progestogen. Rifampicin has a marked effect
      
      
  • antiretroviral e.g. - ritonavir - marked reduction in EE. EE reduced by 40%. Additional and/or alternative contraceptive methods advised
    
    
  • emergency contraceptives e.g - ulipristal acetate
    • theoretical reduction in the efficacy of progestogen-containing contraceptives. Additional precautions required for 14 days (9 days if using or starting POP, 16 days for Qlaira®)
      
      
  • gastrointestinal drugs e.g. - proton pump inhibitors, antacids, H2 receptor antagonists
    • theoretical reduction in plasma concentrations of UPA and may result in decreased efficacy. Concomitant use not recommended
      
      
  • herbal e.g. - St. Johns Wort - is a weak enzyme inducer and has the potential to reduce efficacy
    
    
• drugs that increase contraceptive hormone levels
  • antibacterial e.g. - erythromycin
    
    
• the clinical significance is not known but increased adverse events might be anticipated
  • antifungal e.g. - fluconazole, itraconazole, ketoconazole
    
    
• modest increases in EE and progestogen
  • antiretroviral e.g. - atazanavir
  • NSAID's e.g. - etoricoxib
    • doses of etoricoxib >=60 mg raise ethinylestradiol (EE) levels by approximately 40% or more
      
      
• potential risk of estrogen-related adverse events
• statins e.g. - atorvastatin the clinical significance is not known but likely to be small

Reference

1. Royal College of Obstetricians and Gynaecologists. Faculty of Sexual and Reproductive Healthcare guideline. May 2022. Drug Interactions with Hormonal Contraception.