attention deficit - hyperactivity disorder ( adhd ) is a common developmental disorder in children which often continues into adulthood . it is the most common psychiatric disorder in children so that it constitutes about 50% of referrals to child psychiatry clinics . half of clinical samples have disruptive behavior disorders ( dbds ) , consisting of oppositional defiant disorder or conduct disorder . many longitudinal studies have followed children from early childhood to evaluate the impact of early dbds . such dbds have been associated with adult smoking , alcohol and illicit drug use , physical aggression , and risky sexual behavior ; repeated or serious crimes , and involvement in destructive offenses . therefore , evidence - based treatments to mitigate these problems in early childhood are clearly warranted . treatment of behavioral disorders at an early age may help to prevent long - term disability . the cornerstone of treatment for these disorders is behavioral therapy , but psychotherapy may not be enough . therefore , physicians in daily practice sometimes require pharmacological intervention in preschool children with chronic , disabling , or resistant behavioral problems . pharmacotherapy with atypical antipsychotics is increasing quickly in child and adolescent psychiatry , and this is especially the case for children with dbds . for example , a study examining the prescription trend of atypical antipsychotics among 11,700 arkansas medicaid - covered children under age 18 who were newly treated with atypical antipsychotics from 2001 through 2005 found that the number of children receiving the medications doubled during this period . the most common condition was adhd , followed by depression , conduct disorder , oppositional defiant disorder , and adjustment reactions . aripiprazole has a unique pharmacological profile , as a partial agonist at the dopamine d2 and serotonin 5ht1a receptors and an antagonist at the serotonin 5ht2a receptor ; this drug has few side effects ( such as extrapyramidal syndrome , hyperprolactinemia , weight gain , metabolic disorders , and sedation ) which are common problems with other antipsychotic drugs . efficacy and tolerability of aripiprazole in children and adolescents have been well - demonstrated in many clinical studies , which supported approvals granted by the us food and drug administration for schizophrenia , bipolar diseases , and irritability associated with autistic disorder in children and adolescents . this study was conducted to compare the efficacy and safety of risperidone and aripiprazole in the treatment of preschool children with dbd comorbid with adhd . this study was a randomized clinical trial conducted in the child psychiatry clinic affiliated with a university in southwest iran . children 36-year - old with oppositional defiant disorder comorbid with adhd , according to the diagnostic criteria of diagnostic and statistical manual of mental disorders , revision iv - text revised , were enrolled into the study . children with mental retardation or other developmental disorders such as autism , chronic physical , or neurological illness , or those receiving other psychotropic drugs were excluded from the study . after the aims of the study were fully explained to the parents , they were asked to complete a consent form to participate in the study , whereas patient anonymity was preserved . treatment was initiated with 0.25 mg risperidone once daily , increased by 0.25 mg weekly , to a maximum dose of 2 mg / day , or 2.5 mg aripiprazole , increased by 2.5 mg weekly , to a maximum dose of 10 mg / day . for blinding , the patients were rated by a clinician who was blind to group assignment of the patients . at the beginning of the treatment , shortened and revised version of conners parent rating scale , clinical global impressions ( cgi ) scale , body weight , fasting blood glucose ( fbs ) , and serum prolactin were measured . then at weeks 2 , 4 , and 8 , cgi and conners scale were readministered . the instrument of data gathering was shortened and revised conners parent rating scale , which contains 27 items in four subscales : oppositional defiant , inattention , hyperactivity , and adhd subscales . the data were analyzed by spss statistics software - ibm , and the mean score ( standard deviation ) of variables was calculated . then , mean scores between the two groups were compared by analysis of variance ( anova ) , and independent and paired t - test . the two groups were not significantly different in age , gender , family history , and severity of illness [ table 1 ] . demographic characteristics of participants anova showed that mean scores of conners rating scale had statistically significant decrease in both groups , and t - test and paired comparison of different steps showed that there was significant difference between measurements at steps 1 and 2 ( p = 0.00 ) , but there was no significant difference between steps 2 and 3 ( p = 1.00 and 0.431 for aripiprazole and risperidone groups , respectively ) and steps 3 and 4 ( p = 0.88 and 0.291 for aripiprazole and risperidone groups , respectively ) . all subscales of the conners rating scale showed a significant decrease between steps 1 and 2 in both groups ( p < 0.001 ) . scores of conners rating scale subscales results of cgi - improvement ( cgi - i ) showed that 7 ( 35% ) patients of aripiprazole group had cgi - i scores of 1 or 2 ( much or very much improvement ) at week 8 , which means significant improvement . there was no significant difference between two groups at endpoint ( p = 0.898 ) . similarly , no significant difference was observed between the two groups in cgi - severity ( p = 0.380 ) at the endpoint . the mean increase in body weight was 1.2  1.13 kg in aripiprazole group and 1.25  0.68 kg in risperidone group , with no significant difference ( p = 0.894 ) . the mean increase in fbs was  0.25  7.67 mg / dl in aripiprazole group and 3.5  13.43 in risperidone group , with no significant difference ( p = 0.671 ) . the mean increase in serum prolactin level was 1.37  0.87 in aripiprazole group and 22.38  3.61 in risperidone group , with a significant difference ( p = 0.00 ) . six parents in risperidone group ( 30% ) , and 3 parents in aripiprazole group ( 15% ) reported tolerance to drug effect , which was not a statistically significant difference ( p = 0.289 ) . the dose of aripiprazole was between 1.25 and 10 mg in week 8 of treatment ; with a mean of 4.69  1.25 mg . dose of risperidone was between 0.25 and 2 mg in week 8 ; with a mean of 1.05  0.51 mg . frequency of side effects was not different between the two groups ( p > 0.05 ) . four parents in aripiprazole group decided to discontinue the medication due to severely increased appetite ( one patient ) , sleepiness ( two patients ) , and agitation ( one patient ) . five parents in risperidone group discontinued medication due to tolerance to the drug effects ( three patients ) , epistaxis ( one patient ) , and severely increased appetite ( one patient ) . four parents in the risperidone group and three parents in aripiprazole group reported no side effects . results of this study showed that clinical improvement was seen at the 2 week of treatment with both drugs , and there was no further improvement with continuing medication or increasing the dosage . some patients developed tolerance to the medication effects , which was more frequent in patients receiving risperidone . in a chart review study of 25 preschool - aged children treated with risperidone for dbds , tolerance to risperidone severity of illness at the beginning of treatment , and at weeks 2 , 4 , and 8 showed no statistically significant difference between the two groups , which means that both medications were equally effective in these patients . 35% of the patients in aripiprazole group and 30% in risperidone group experienced significant clinical improvement at week 8 of treatment based on cgi - i scores . in this study , some parents refused to increase the dose of medication as prescribed , which may have affected the results . in the chart review study of 25 preschool - aged children treated with risperidone for dbds , the majority of subjects ( 72% ) showed  much  to  very much  improvement in target disruptive behavior symptoms , and the duration of risperidone treatment ranged from 2 to 60 weeks ( 18.87  15.19 ) , which is longer than this study . in this study , there were no significant differences in weight gain and fbs level change between the two groups , but the increase in prolactin level in the group treated with risperidone was significantly higher than those treated with aripiprazole . no serious or life - threatening side effects were reported , and none of the patients experienced drug - induced extrapyramidal side effects . results of an 8-week study on bipolar children , 16-week study on patients with pervasive developmental disorders , and a 6-month study along with placebo showed that risperidone at low dose effectively controls prolonged behavioral disorders in preschool - aged children . a retrospective study on children with aggressive behaviors associated with results of these studies have shown obviously increased weight and increased prolactin levels in the patients taking risperidone . in a 6-week , double - blinded study of 118 children with severely disruptive behaviors and subaverage intelligence , receiving 0.020.06 mg / kg / day of risperidone or placebo , the risperidone group showed significantly greater improvement on the conduct problem scale from week 1 through the endpoint . mean weight increases of 2.2 kg and 0.9 kg occurred in the risperidone and placebo groups , respectively . in an open - label study of eight normally developing preschool children with conduct disorder , treated with risperidone for 8 weeks , they detected statistically significant increase in prolactin level ( p < 0.05 ) , but no clinical symptoms associated with prolactinemia . in another open - label study of risperidone monotherapy on 31 children and adolescents 415 years of age with pediatric bipolar disorder and adhd , results showed that improvement in adhd symptoms was contingent on improvement in manic symptoms . although both hyperactive / impulsive and inattentive adhd symptoms were significantly improved with risperidone , improvement was modest , and only 29% of the participants showed a 30% reduction in adhd scores and had a cgi - i of 1 or 2 . in a study assessing risperidone introduction into stimulant for severe aggression in 168 612-year - old children with adhd , risperidone provided a moderate but variable improvement in aggressive and other seriously disruptive behaviors in children . results of a 6-week open study on 23 hyperactive children aged 812 years old treated with aripiprazole , at a mean dose of 6.7 mg taken daily , showed significant improvement in symptoms and function . the most frequently reported adverse events were sedation ( 78.3% ) and headache ( 47.8% ) . in a study on patients with tourette 's disorder and adhd , the drug was well - tolerated , and none of the patients discontinued medication due to adverse events . furthermore , the drug led to significant improvement of tourette 's disorder and had a modest effect on the comorbid adhd . antipsychotic drugs , risperidone and aripiprazole , are relatively effective and safe for treatment of dbds comorbid with adhd in preschool - aged children . side effects are generally mild to moderate but given the high rate of side effects of these drugs , they should be used with caution in this age group . we recommend further studies with larger sample size and longer follow - up as well as to compare aripiprazole and risperidone with other atypical antipsychotics and ritalin , or behavioral interventions in the treatment of behavioral disorders in preschool children . we recommend further studies with larger sample size and longer follow - up as well as to compare aripiprazole and risperidone with other atypical antipsychotics and ritalin , or behavioral interventions in the treatment of behavioral disorders in preschool children .
although pharmacotherapy with atypical antipsychotics is common in child psychiatry , there has been little research on this issue . to compare the efficacy and safety of risperidone and aripiprazole in the treatment of preschool children with disruptive behavior disorders comorbid with attention deficit - hyperactivity disorder ( adhd ) . 
 randomized clinical trial conducted in a university - affiliated child psychiatry clinic in southwest iran . 
 forty 3 - 6-year - old children , diagnosed with oppositional defiant disorder comorbid with adhd , were randomized to an 8-week trial of treatment with risperidone or aripiprazole ( 20 patients in each group ) . 
 assessment was performed by conners rating scale - revised and clinical global impressions scale , before treatment , and at weeks 2 , 4 , and 8 of treatment . 
 the data were analyzed by spss version 16 . 
 mean scores between the two groups were compared by analysis of variance and independent and paired t - test . 
 mean scores of conners rating scales were not different between two groups in any steps of evaluation . 
 both groups had significantly reduced scores in week 2 of treatment ( p = 0.00 ) , with no significant change in subsequent measurements . 
 rates of improvement , mean increase in weight ( p = 0.894 ) , and mean change in fasting blood sugar ( p = 0.671 ) were not significantly different between two groups . 
 mean serum prolactin showed a significant increase in risperidone group ( p = 0.00 ) . both risperidone and aripiprazole 
 were equally effective in reducing symptoms of adhd and oppositional defiant disorder , and relatively safe , but high rates of side effects suggest the cautious use of these drugs in children .