Which muscle relaxant is commonly misused in combination with an opioid and a benzodiazepine, producing a heroin-like effect?

• A. Cyclobenzaprine
• B. Carisoprodol
• C. Baclofen
• D. Methocarbamol

Answer: (B)

The key idea is that some muscle relaxants have a higher potential for misuse when layered with other central nervous system depressants like opioids and benzodiazepines. Carisoprodol stands out because it is rapidly metabolized into meprobamate, a sedative-like metabolite that enhances CNS depression. This combination amplifies the sedative and euphoric effects, which can resemble a heroin-like high when paired with opioids and benzodiazepines.

While other muscle relaxants also cause sedation, they don’t share that same potent metabolite that drives strong central depressant effects. Their misuse with opioids or benzodiazepines is less associated with the characteristic heroin-like high, making carisoprodol the best answer here due to its metabolism and abuse potential.