Baclofen (Gablofen, Lioresal) is a medication that treats stiff muscles and spasms, a condition called spasticity, that can happen to people with multiple sclerosis and other nerve diseases. Normally, your muscles get electrical signals from your nerves that tell them when to tense and relax. Spasticity happens when these signals become uneven, usually because the nerves have been damaged. This makes muscles tense up or move when you don’t want them to. Baclofen works by restoring the normal signals. It can help you move your muscles more normally.