What medication is most appropriate for a patient with Multiple Sclerosis experiencing muscle spasticity?

Baclofen is the most appropriate medication for a patient with Multiple Sclerosis who is experiencing muscle spasticity. Baclofen is a centrally acting muscle relaxant that works by inhibiting the transmission of afferent impulses in the spinal cord, leading to a reduction in muscle tone and spasticity. This mechanism is especially beneficial for individuals with Multiple Sclerosis, as spasticity is a common symptom that can significantly impact mobility and quality of life.

The other medications listed serve different purposes. Topiramate is primarily used as an anticonvulsant and for migraine prophylaxis, not specifically for muscle spasticity. Risperidone is an antipsychotic used to treat certain mental health disorders, such as schizophrenia and bipolar disorder, and does not address muscle spasticity associated with neurological conditions. Prazosin is an alpha-1 adrenergic blocker generally used to treat hypertension and symptoms of benign prostatic hyperplasia; it does not have an indication for the management of muscle spasticity in Multiple Sclerosis.

Therefore, Baclofen's specific action on muscle relaxation makes it the correct choice for managing muscle spasticity in patients with Multiple Sclerosis.