Simvastatin is a statin. It's a synthetic derivate of a fermentation product of Aspergillus Terreus. Simvastatin is out of patent protection and the least expensive statin available. There is research linking it to disturbed sleep, eventually due to it being fat soluble and being able to cross the blood-brain barrier. An alternative might be Pravastatin which is water soluble and apparently does not cause sleep issues.
Also known as: Zocor, Lipex