Muscle relaxants are categorized by what characteristic?

• A. Mechanism of action
• B. Time to onset
• C. Brand name
• D. Indication

Answer: (A)

Classification of muscle relaxants is based on their mechanism of action. This grouping matters because it reflects how the drug produces its effect and helps anticipate both therapeutic benefits and potential side effects. Central-acting agents depress the CNS to reduce overall muscle tone—think of baclofen, diazepam, and tizanidine as examples that modulate neural signals before they reach the muscles. Peripheral-acting agents work at the muscle or the neuromuscular junction—dantrolene lowers calcium release in muscle cells, while botulinum toxin prevents acetylcholine release, yielding localized relaxation. Because the defining feature is how the drug works, other attributes like time to onset, brand name, or indications don’t define the category, and they can vary independently of mechanism.