Pharmacology of dantrolene sodium in children

Dantrolene sodium was administered orally to 19 children with chronic spasticity. Plasma levels of the drug reached their peak 5 to 6 hr after ingestion; usually the drug was detectable in plasma for 24 hr or more after ingestion. A semilog time concentration plot was used to estimate the drug's half life in plasma, half input time, and peak concentration time. The values were close to those reported for adults. In children as in adults, dantrolene sodium is metabolized to a 5 hydroxy form and reduced to an acetylated amine derivative. Both forms were found in children's urine, but the reduced form was not found in plasma. Of the total excretion of drug and metabolites, about 79% was the hydroxy form, 17% the reduced acetylated form and 4% the unaltered drug. Side effects consisted chiefly of drowsiness and dizziness and were prominent only in single dose studies; they were not a problem in a 2 wk study with the drug given 4 times per day. It is concluded that dantrolene sodium is safe for administration to children in divided doses of 4 to 12 mg/kg/day for periods of 2 wk, the maximum period used in this study.