However, pharmacological agents are frequently used. They reduce muscle overactivity by decreasing the excitability of motor pathways at the level of the central nervous system, the neuromuscular junction, or the muscle itself. Antispastic drugs possess different mechanisms of action, and act either centrally or peripherally. Agents acting peripherally, such as dantrolene, act at neuromuscular sites. Other agents occasionally used out of licence for their antispastic properties include clonidine and gabapentin.
Diazepam is the oldest antispastic agent.
In high doses diazepam is effective in relieving spasticity. However, drowsiness, the risk of overdose, and the development of physical and psychological dependence with regular use limit its clinical use. Diazepam may be useful in small doses at night to help nocturnal spasms. Baclofen is the most widely used antispastic agent. The net effect is inhibition of spinal reflexes.