Plasma levels and efficacy of imipramine treatment for enuresis

Abstract

Objective: To determine the relationship between serum drug level and treatment efficacy in enuretic children treated with imipramine (IMI).

Method: Eighteen children with primary nocturnal enuresis recruited from an ambulatory enuresis clinic population were the subjects of the study. After a baseline period of 2 weeks, children received placebo for 1 week followed by treatment with IMI in increasing dosages (1.0 mg/kg, 1.5 mg/kg, 2.0 mg/kg, and 2.5 mg/kg), each dosage being given for 2 weeks. Steady state IMI and desipramine levels were determined in each child for each dosage. Medication response ([drug % dryness-placebo % dryness] divided by [100%-placebo % dryness]) was determined for each dosing interval.

Results: Average dryness increased from 27.8% on placebo to 73% with 2.5 mg/kg of IMI. The overall correlation between medication response and combined serum level was .26 (p < .05). Side effects were monitored throughout the study and were found to be rare.

Conclusions: The efficacy of IMI over placebo in reducing the frequency of nocturnal enuresis in children was confirmed. Efficacy was moderately but significantly related to increasing mg/kg dose. A higher serum level tended to be associated with a better response, but there was at least 700% variation in serum level between subjects at every dosage. Monitoring serum levels of imipramine in children with idiopathic functional nocturnal enuresis treated with that medication has a limited but real usefulness in clinical management.