Colesevelam may decrease the absorption of glyburide into the body, perhaps making it less effective. Glyburide should be taken at least four hours before a dose of colesevelam to avoid this interaction. If you take colesevelam twice a day and have trouble timing the doses of glyburide and colesevelam, ask your healthcare provider about taking colesevelam just once a day instead of twice a day, as this can make avoiding this interaction easier.

 

Colesevelam may decrease the absorption of levothyroxine into the body, perhaps making it less effective. Levothyroxine should be taken at least four hours before a dose of colesevelam to avoid this interaction.

 

Colesevelam has been shown to decrease the absorption of certain birth control pills (those that contain ethinyl estradiol in combination with norethindrone), perhaps increasing the risk of pregnancy. Colesevelam has not been studied in combination with other birth control pills, and it is likely to interact similarly with other birth control pills as well. Birth control pills should be taken at least four hours before a dose of colesevelam.

 

There have been reports of colesevelam interacting with phenytoin, decreasing its absorption and perhaps making it less effective. In order to avoid this interaction, take phenytoin at least four hours before a dose of colesevelam.

 

Although there have been reports that colesevelam may interact with warfarin, studies have not demonstrated any interaction between these two medications. Interactions may occur due to a decreased absorption of vitamin K, since vitamin K can affect warfarin. Check with your healthcare provider in this situation, as you may need to be monitored more closely.