An attempt to minimize polypharmacotherapy, to discontinue the use of phenobarbital, and to assess the relation between drug levels and antiepileptic effect in institutionalized severely retarded children is reported from the Department of Pediatrics, St. Goran’s Hospital, Stockholm, and the Division of Clinical Pharmacology, University Hospital, Uppsala, Sweden. Nine severely mentally retarded patients with severe epilepsy were studied during a three year period by a multidisciplinary team. Combination therapy with two or three drugs gave the best antiepileptic effect and monotherapy was possible in only two patients. Phenobarbital withdrawal was possible in two of four patients. Regular phenytoin serum monitoring was necessary to avoid high levels that could be unnoticed for long periods and possibly result in chronic long-term side effects. 
COMMENT. The tendency among neurologists to attempt conversion from polytherapy to monotherapy in severely retarded institutionalized patients may be hazardous and inadvisable. This study has demonstrated that polytherapy is frequently required. The recognition of anticonvulsant side effects may be more difficult in retarded patients compared to clinic patients and frequent serum drug monitoring is important.