Abstract
To The Editor:
N
Case Report
A 5.5 year-old-boy with intellectual disabilities (ID) was admitted to our clinic with self-mutilation and pica, such as eating stone, soil, stool, and cloth. In addition, he had epilepsy, and had been treated with valproic acid 900 mg/day since he was 1 year old. His valproic acid blood level was 35.34 μg/mL. Blood test results for ferritin, hemoglobin, vitamin B12, copper levels, and thyroid functions were normal. Second-generation antipsychotics (SGA), except for the treatment of psychotic symptoms in psychiatric diseases, are only used to treat impulsivity or aggression seen in various disorders such as mental retardation (Schatzberg and Nemenoff 2013). It is known that risperidone is the most studied and most widely used SGA to treat child patients (Governale and Mehta 2009).
Risperidone (0.25 mg/day) was started because of the boy's ID and accompanying behavior problems.
In addition to receiving medical therapy, we asked the patient's parents about his psychosocial behaviors and environmental factors, and then some suggestions were given to the family. The patient was checked 14 days later, and his risperidone dose was increased to 0.5 mg/day. Approximately 10 days later, the patient admitted to the clinic with walking deficit, and could not stand without support. On physical examination, there was found to be limited motor weakness in his lower extremities. There were no other findings, except muscle weakness, on neurological examination. All radiological and blood tests were normal. It has been shown that valproic acid might increase sedation and somnolence when patients took it with antipsychotic medications. In a case report, it was reported that after the addition of risperidone to valproic acid treatment, hyperammonemia and manic behavior were observed (Carlson et al. 2007). In another case report, after the addition of valproic acid to risperidone treatment, catatonia was observed in one patient (Lauterbach 1998). On the other hand, there is some information about risperidone and valproic acid, which are well tolerated when used in combination. In our case, the side effect occurred after a risperidone dose increase; therefore, it was thought that medication was a possible cause, particularly because the symptom disappeared when the risperidone was stopped. After the risperidone dose was decreased from 0.5 mg/day to 0.25 mg/day, motor weakness disappeared within 4 days. The risperidone dose was tapered gradually within 1 week, after which the patient's pica and behavior problems continued.
Discussion
Risperidone, generally, is an effective and well-tolerated medication, and it is the first SGA to have been approved by the United States Food and Drug Administration (FDA) in children and adolescents, even though our knowledge of it is still limited (Harrison et al. 2012). When we searched the literature, we did not find any previous information about motor weakness related to risperidone. Considering that antipsychotic medications are likely to cause side effects, particularly in children with ID, these medications should be used carefully.