Efavirenz is one of several medicines that can lower the amount of Axitinib in the blood. It does this by speeding up the liver enzymes CYP3A4 and CYP3A5, which break Axitinib down faster. Because of this, using the two together should be avoided if possible.
These medicines can affect each other in a serious way. Do not start taking them together unless your doctor has said it is OK. If you already take both, do not stop either one on your own: speak to your doctor or pharmacist soon.