From the Research
Dronabinol may potentially reduce the effectiveness of oral contraceptives, though direct evidence is limited, and women taking both medications should consider using additional contraceptive methods to ensure protection against pregnancy. The primary concern is that dronabinol, being metabolized by the liver using the same cytochrome P450 enzyme system that processes many oral contraceptives, could induce certain liver enzymes, potentially accelerating the breakdown of contraceptive hormones and reducing their effectiveness 1. This interaction is similar to what occurs with other medications like certain antibiotics, antiseizure medications, and St. John's Wort.
Key Considerations
- Dronabinol is metabolized by the cytochrome P450 enzyme system, which also processes many oral contraceptives, creating a potential for drug interactions that could affect contraceptive hormone levels in the bloodstream.
- The interaction could lead to reduced effectiveness of oral contraceptives, similar to interactions with other medications.
- Women using dronabinol for approved indications should discuss this potential interaction with their healthcare provider.
Recommendations
- Women taking dronabinol and oral contraceptives should consider using additional contraceptive methods, such as condoms, during dronabinol treatment and for at least one week afterward as a precautionary measure until more definitive research becomes available.
- Healthcare providers should be aware of this potential interaction and counsel their patients accordingly, especially when prescribing dronabinol for conditions like chemotherapy-induced nausea or AIDS-related appetite loss.
Evidence Basis
The most recent and highest quality study relevant to this question is from 2005, which investigated the effect of oral contraceptives on the metabolism of tizanidine, demonstrating that oral contraceptives can significantly inhibit the cytochrome P450 1A2 enzyme, leading to increased plasma concentrations and effects of certain drugs 1. While this study does not directly address dronabinol and oral contraceptives, it highlights the potential for oral contraceptives to interact with drugs metabolized by the cytochrome P450 system, supporting the concern for potential interactions with dronabinol.