Mexiletine may also be of use in patients experiencing refractory pain and is also effective for treating muscle stiffness resulting from myotonic dystrophy (Steinert's disease) or nondystrophic myotonias such as myotonia congenita (Thomsen disease).

Diphenhydramine injection is also used alone or with other medications to treat shaking (tremor) and muscle stiffness caused by Parkinson's disease when medication cannot be given by mouth.

Anticholinergic medicines are used to treat muscle stiffness, tremors, and spasms.

Diphenhydramine is also used alone or with other medications to treat shaking (tremor) and muscle stiffness caused by Parkinson's disease.

Several medicines may be used to treat muscle stiffness (spasticity) caused by multiple sclerosis (MS).