In this article in the New York Times Ask Well discusses how CoQ10 may interact with certain drugs.
Sometimes natural product can work very well and that can be the nature of their interaction with other medications. CoQ10 can reduce blood pressure so when combined with blood pressure medication can see it amplify the effects of blood pressure medication. CoQ10 can possible lead to dangerous lower blood pressure levels.
It may also lower blood sugar so it may also cause a problem for those taking medication to control their blood sugar. The additional lowering could result in low blood sugar.
CoQ10 also interact with blood thinners so anyone taking them need to use extra caution.