Alcuronium (diallylnortoxiferine) is a semi-synthetic substance prepared from C-toxiferine I a bis-quaternary alkaloid obtained from Strychnos toxifera. Alcuronium is a neuromuscular blocking (NMB) agent, alternatively referred to as a skeletal muscle relaxant. Alcuronium is used for endotracheal intubation and to produce muscle relaxation in general anesthesia during surgical procedures. The pharmacological action of alcuronium is readily reversed by neostigmine, and it produced little histamine release. The major disadvantage of alcuronium is that it elicits a vagolytic effect produced by a selective atropine-like blockade of cardiac muscarinic receptors.

Thiocolchicoside is a muscle relaxant that has been authorised by national procedures in several EU Member States for use by mouth or injection into the muscles in the treatment of painful muscular disorders. Thiocolchicoside is marketed under the brand name Muscoril among others. Thiocolchicoside (TCC) is used clinically for its muscle relaxant, anti-inflammatory, and analgesic properties, and it has been shown to interact with gamma-aminobutyric acid (GABA) type A receptors (GABAARs) and strychnine-sensitive glycine receptors in the rat central nervous system.

Gallamine is a synthetic non-depolarizing neuromuscular blocking agent. It has been used to produce relaxation of skeletal muscle during surgery.

Febarbamate is a derivative of barbituric acid and carbamate, used for the treatment of generalized anxiety and alcohol withdrawal syndrome. The drug was marketed in Europe in the 1980s as a single agent or in combination with difebarbamate and phenobarbital, but it was later withdrawn from the market because of the potential risk of liver damage.

Pridinol mesilate is a centrally acting muscle relaxant that is used in the symptomatic treatment of muscle spasm. It is also used as the hydrochloride salt for its antimuscarinic activity in the management of parkinsonism.

Tolperisone is a centrally acting muscle relaxant first synthesized in 1956 and used in clinical practice since the 1960’s. Tolperisone is an aryl alkyl β-aminoketone with an asymmetric carbon atom α to the carbonyl group. The dextrorotatory enantiomer was reported less effective, however, no detailed analyses of the enantiomers are available. The precise mechanism of action of tolperisone is not fully known. The most prominent effect of tolperisone is its inhibitory action on pathways of spinal reflexes. It suppresses the mono and polysynaptic reflex transmission by both pre-synaptic and post-synaptic mechanisms.

Eperisone is an antispasmodic drug approved in Japan for the treatment of of diseases characterized by muscle stiffness and pain. It is believed that eperisone exerts its effect through inhibition of sodium channels. The drug is still being marketed in Asia under the name Myonal (Square Pharmaceuticals).

Tetrazepam was the most widely prescribed muscle relaxant in Germany. After a series of studies, which have shown, that tetrazepam caused cutaneous adverse effects and toxic epidermal necrolysis, the drug was withdrawn from the market.

Phenprobamate (3-phenylpropylcarbamate, Gamaquil, Isotonil) is a centrally acting muscle relaxant with mild sedative and anticonvulsant effects. Muscle relaxants can enhance and prolong the effect of narcotic drugs and enable to obtain same effect with a smaller amount of alcohol or illicit substance. Almost all of the centrally acting muscle relaxants have varying sedative effects on which their abuse potential mainly depends. Overdose is similar to barbiturates. Its mechanism of action is probably similar to meprobamate. Phenprobamate was previously used in humans as an anxiolytic, and is still sometimes used in general anesthesia and for treating muscle cramps and spasticity. Phenprobamate is still used in some European countries, but it has generally been replaced by newer drugs. Phenprobamate is metabolized by oxidative degradation of the carbamate group and ortho-hydroxylation of the benzene ring, and is eliminated in urine by the kidneys. Doses range from 400 to 800 mg, up to 3 times a day.

Atracurium is an intermediate-duration, nondepolarizing, skeletal muscle relaxant for intravenous administration. It is used, as an adjunct to general anesthesia, to facilitate endotracheal intubation and to provide skeletal muscle relaxation during surgery or mechanical ventilation. Most adverse reactions were suggestive of histamine release. Common side effects include flushing of the skin and low blood pressure. Drugs which may enhance the neuromuscular blocking action of atracurium include: enflurane; isoflurane; halothane; certain antibiotics, especially the aminoglycosides and polymyxins; lithium; magnesium salts; procainamide; and quinidine.