Muscle Relaxants

Centrally acting relaxants: they work on the central nervous system rather than on the muscle fibre, so the relaxation and the sedation are one effect and not an effect plus a side effect. Past that they share nothing. Baclofen is a GABA-B agonist, tizanidine an α₂ agonist, cyclobenzaprine and orphenadrine are antimuscarinic and structurally close to the tricyclics, and methocarbamol's mechanism is poorly characterised.

The class name therefore predicts very little. Baclofen has a withdrawal syndrome of its own — abrupt discontinuation after sustained use can bring seizures and delirium — and in overdose produces deep unconsciousness; the antimuscarinic members add to the deliriants' load. All of them add to the sedation of alcohol, opioids and benzodiazepines. Carisoprodol is filed under Depressants with the carbamates, because it is metabolised to meprobamate and the dependence belongs there.