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Plasma levels and efficacy of imipramine treatment for enuresis
G K Fritz1, R M Rockney, A S Yeung
1Brown University/Rhode Island Hospital, Providence 02903.
Insights
Imipramine (IMI) effectively treats childhood nocturnal enuresis, with higher doses showing better results. While serum drug levels correlate with efficacy, significant individual variations exist, suggesting limited but useful clinical monitoring.
Area of Science:
- Pediatric Nephrology
- Clinical Pharmacology
Background:
- Nocturnal enuresis is a common condition in children.
- Imipramine is a tricyclic antidepressant used off-label for enuresis treatment.
- Understanding the relationship between imipramine serum levels and treatment outcomes is crucial for optimizing therapy.
Purpose of the Study:
- To investigate the correlation between serum imipramine levels and treatment efficacy in children with nocturnal enuresis.
- To evaluate the dose-response relationship of imipramine in this pediatric population.
Main Methods:
- A study involving 18 children with primary nocturnal enuresis.
- A placebo-controlled, dose-escalation design using imipramine (1.0-2.5 mg/kg).
- Measurement of steady-state serum imipramine and desipramine levels and calculation of medication response based on dryness percentage.
Main Results:
- Imipramine significantly increased dryness percentage compared to placebo, reaching 73% at the highest dose.
- A moderate but significant positive correlation (r=0.26, p<0.05) was found between medication response and combined serum drug levels.
- Side effects were infrequent, and substantial inter-individual variability (over 700%) in serum levels was observed at each dosage.
Conclusions:
- Imipramine is an effective treatment for childhood nocturnal enuresis.
- Treatment efficacy is linked to both dosage and serum drug concentration.
- While serum level monitoring has limitations due to high variability, it offers some clinical utility in managing imipramine therapy 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.