The fragile X syndrome, considered the most common cause of inherited mental retardation, comprises long narrow face, large and prominent ears, macroorchidism, mental retardation, language deficit, autism, and behavioral disturbances [Chudley and Hagerman, 1987]. Hyperactivity is a significant problem for almost all young fragile-X males [Hagerman et al., 1985; Levitas et al., 1983; Mattei et al., 1991; Finnelli et al., 1985]. Attention deficit disorder (ADD) is frequently diagnosed [Fryns et al., 1984; Hagerman et al., 1985]. Treatment of fragile X syndrome patients is a critical issue for the families because intellectual handicap and behavior problems may create difficulties in social relations [Chudley and Hagerman, 1987]. To date, no specific treatment has been found, although rehabilitative and symptomatic interventions may be helpful [Levitas et al., 1983]. Medical treatment has focused on improving the behavior problems, particularly the ADD and hyperactivity. Central nervous system stimulants were reported to be effective for the treatment of these problems [Hagerman et al., 1988]. However, their use is controversial in retarded patients. The prevailing opinion is that stimulants are not effective in the moderately and severely retarded patients because these drugs further decrease the already limited attention capacity [Aman and Singh, 1982]. The aim of the present preliminary study is to evaluate the efficacy of L-acetylcarnitine (LAC) in improving the behavior of fragile-X patients.

LAC is an acetyl derivative of carnitine detectable in various brain regions from an early stage of development and is required for the transport and use of fatty acids and in energy metabolism. LAC treatment has proven particularly effective in experimental animals (rats) with learning deficits and hyperactivity [Dell’Anna et al., 1997]. In vitro, LAC was shown to inhibit the