Plasma levels and efficacy of imipramine treatment for enuresis.

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.