No medication has been proven effective in treating core characteristics of intellectual disability or autism. Psychotropic medications are frequently used to target psychiatric symptoms in children, adolescents and adults with developmental conditions, despite the little evidence for their efficacy. This article aimed to summarize current evidence on efficacy of pharmacological interventions for the most frequent symptoms and disorders associated to autism and to intellectual disability. And also, novel molecules being studied for core symptoms of these conditions. Electronic databases were searched and supplemented with a hand search. Data were described narratively prioritizing meta-analysis and randomized controlled trials but considering also open label trials and preliminary studies. The main conclusions were that only few drugs showed efficacy for reducing psychiatric symptoms associated to these developmental conditions, mainly risperidone and aripiprazole to treat irritability and methylphenidate and atomoxetine for hyperactivity and attention deficit. Evidence is inconclusive regarding the effectiveness of other drug groups. Novel therapeutic agents showed mixed results and quality of evidence is low; some of these agents aim at biologically targeted pharmacotherapy, which may lead to successful individualized treatment options in the future. To this day, clinicians should use pharmacotherapy with caution, carefully weighing risks and benefits, and as a part of a comprehensive personalized approach.