The primary objective of this study is to establish a safe and effective method of up-titration of captopril for hospital inpatients.

Angiotensin converting enzyme inhibitors (ACEi) are one of the most frequently prescribed pediatric cardiac medication and overall their safety in children is widely accepted. Pediatric formulary recommendations for ACEi suggest starting with a low initial dose (0.1 mg/kg), to avoid hypotension, and up-titration for a maintenance dose. However, side ranges are quoted for maintenance doses and no guidance is given as to the best method of up-titration, The physician is left uncertain of the optimal dose and how best to achieve it.

The ultimate goal of this study is to be in a position to provide physicians caring for children with heart disease information about how to safely up-titrate this widely used medication, and by doing so to improve dosing in the wider pediatric population.

Inclusion Criteria:

• Pediatric cardiology in-patients at The Hospital for Sick Children
• Primary physician has decided to commence ACEi (the division has agreed that our institutional choice will be to start patients on captopril and up-titrate to optimal dose before converting to other ACEi)
• Patients who have been initiated on captopril within the prior 24 hours, but have not yet started up-titration, will be eligible to be randomized

Exclusion Criteria:

• Known sensitivity to ACEi
• Infants on the neonatal intensive care unit
• Treatment with any ACEi for more than 24 hours within the preceding 6 months
• Age > 18 years