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Mephenesin: abuse and dependence

Mephenesin is a muscle relaxant with psychotropic effects, leading to abuse and dependence. It is better to avoid mephenesin, especially in patients with a history of abuse and dependence.

Mephenesin is a muscle relaxant whose efficacy has not been extensively or thoroughly evaluated, with sedative effects that have been known for a long time. Its adverse effects are chiefly sleepiness, nausea, vomiting, and severe allergic reactions.

In France, since 2010, a rise in the number of cases of mephenesin abuse and dependence has been observed. Most of these patients had a history of dependence on other psychotropic drugs, both legal and illegal substances, or medication. The daily consumption of most mephenesin-dependent patients was four times higher than the maximum recommended dose, i.e. around 12 g of mephenesin or one packet of 500 mg tablets a day.

Patients state they are seeking a sedative effect, a “high”, or relief from physical or psychological pain. In three cases, withdrawal was followed by withdrawal symptoms such as shivering, anxiety and aggression.

To relieve painful muscular contractions, a brief rest and paracetamol sometimes help. It is better not to start mephenesin treatment which exposes patients to a risk of dependence.

Patients taking mephenesin should be informed of the risk of dependence, and it is better to suggest gradually stopping the treatment. Confronted with repeated requests for mephenesin, the healthcare professional should respond in the same way as for other dependences.

In short, avoid mephenesin, especially in patients with a history of abuse and dependence.

©Prescrire 1 May 2013

"Mephenesin: abuse and dependence" Prescrire Int 2013; 22 (138): 127-128. (Pdf, subscribers only).

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See also:

Mephenesin: anaphylactic
shock and acute generalised
exanthematous pustulosis
Prescrire Int 2012;
21 (125) : 70.
Pdf, subscribers only