June 20 (Reuters) - The European Medicines Agency has

begun a review of medicines to treat alcohol dependency that

contain sodium oxybate, it said on Friday, following concerns of

potential misuse or abuse.

The regulator's review comes after the French medicines

agency raised questions about the effectiveness of a generic

drug with sodium oxybate to treat the condition, based on three

studies, and warned of a possible risk of abuse due to its

effects on the brain.

The active ingredient attaches itself to receptors for the

neurotransmitter GABA in the brain and the spinal cord, calming

their activity.

Sodium oxybate is sold as a syrup in Austria and as an oral

solution in Italy for alcohol dependency under the name Alcover

by privately owned D&A Pharma.

In Europe, Jazz Pharmaceuticals' ( JAZZ ) drug containing

sodium oxybate, Xyrem, is approved to treat narcolepsy - a

neurological disorder characterized by excessive daytime

sleepiness and sudden muscle weakness.

D&A Pharma and Jazz did not immediately respond to Reuters

request for comment.

Alcover is used to treat symptoms of alcohol withdrawal such

as agitation, shaking and problems sleeping, either alone or as

an add-on treatment. It is also used to support long-term

abstinence from alcohol, along with counseling and social

rehabilitation.

The EMA's human medicines committee will assess the

benefit-risk balance and evaluate measures to prevent misuse.

Sodium oxybate is a form of GHB, or gamma hydroxybutyrate,

which is a colorless and tasteless liquid. U.S. regulators have

previously raised concerns about misuse of GHB as a party or

"date-rape" drug due to its strong sedative effects.