Final answer:
Lioresal (Baclofen) is administered to help alleviate spasticity in the lower extremity after a stroke, as it is a central nervous system muscle relaxant specifically for this condition.
Step-by-step explanation:
When a patient is experiencing spasticity in the lower extremity following a stroke, the appropriate medication to administer is Lioresal (Baclofen). Baclofen is a muscle relaxant that works on the central nervous system to relieve spasticity. It is commonly prescribed to manage symptoms associated with multiple sclerosis, spinal cord injuries, or diseases affecting the spinal cord, and can also be used to support stroke patients. Other medications listed, such as Pregabalin (Lyrica), Diphenhydramine (Benadryl), and Heparin, serve different purposes and are not primarily used to treat spasticity.