Lenalidomide Capsules (Lenakast 5) is an anti-cancer medication used to treat cancers of the blood. Lenalidomide 25mg Capsules (Lenakast 5) is a tablet that contains Lenalidomide in doses of 5, 10, and 25 mg, as well as additional components. Lenalidomide Capsules function by blocking the growth of blood vessels, which supply nutrition to malignant cells (Anti-angiogenesis). Because lenalidomide capsules may cause a decrease in white blood cells and platelets, which are needed to fight infection, haemoglobin, and blood clotting, you may need to have regular blood tests before and throughout treatment.