Plan B Drug Interactions

Certain barbiturates, seizure medications, and antibiotics may interfere with Plan B. Drug interactions such as these could decrease the level of Plan B in your blood, possibly increasing the risk of pregnancy. However, it is not known for certain if these medications truly have an effect on Plan B. If you have any concerns about possible drug interactions with Plan B, you should contact your healthcare provider.

An Introduction to Plan B Drug Interactions

Plan B® (levonorgestrel) can potentially interact with several other medicines. Some of the medicines that may lead to Plan B drug interactions include:
 
  • Aminoglutethimide (Cytadren®)
  • Aprepitant (Emend®)
  • Barbiturate medications, such as:
 
    • Amobarbital (Amytal®)
    • Butalbital (Fioricet®, Fiorinal®)
    • Pentobarbital (Nembutal®)
    • Phenobarbital (Luminal®)
    • Primidone (Mysoline®)
    • Secobarbital (Seconal®)
 
 
 
  • Some (but not all) antibiotics
  • St. John's wort (Hypericum perforatum).
     

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Written by/reviewed by: Kristi Monson, PharmD; Arthur Schoenstadt, MD
Last reviewed by: Kristi Monson, PharmD;
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