Buspirone attenuates methylphenidate-induced growth inhibition

Methylphenidate is effective in the treatment of attention deficit hyperactivity disorder (ADHD) in children and adults, but its long term use can cause potential adverse effect on growth rate and variable effects on appetite. Previous studies have shown that long term administration of psychostimulant drugs increases the effectiveness of somatodendritic 5-hydroxytryptamine (5-HT)-1A receptors. Repeated administration of buspirone attenuates the effectiveness of somatodendritic 5-HT1A receptors. The present study was designed to test the hypothesis that co-administration of buspirone may attenuate methylphenidate-induced effects on growth rate and food intake. Growth rate was calculated weekly in terms of change in body weight as percentage of preceding week's body weight and food intake was calculated weekly by subtracting the amount of food left in the hopper from the amount of food placed in the hopper as % in preceding week mg/gm of body weight after long-term administration of methylphenidate, buspirone and their co-administration. Long term oral administration of methylphenidate at a dose of 2.0 mg/kg/day decrease growth rate, but co-administration of buspirone at a dose of 10 mg/kg/day attenuates effect of methylphenidate on growth rate however food intake was significantly greater in all treated groups after 3 weeks of treatment. It is suggested that buspirone may oppose methylphenidate-induced growth inhibition by decreasing the sensitivity of somatodendritic 5-HT1A receptors. These findings may help to extend future therapeutics in ADHD.