To determine the frequency of concurrent use of conventional medications and natural health products (NHP) and their potential interactions in children arriving at an emergency department.

A survey of parents and patients 0 to 18 years at a large pediatric ED in Toronto, Ontario, Canada.

A total of 1804 families were interviewed in this study. Concurrent drug-NHP use was documented in 355 (20%) of patients and 269 (15%) of NHP users were receiving more than one NHP simultaneously. Theoretically possible NHP-drug or NHP-NHP interactions in the preceding 3 months were identified in 285 (16%) children. There were 35 different NHP-medication interaction pairs and 41 NHP-NHP interaction pairs. NHP-medication interactions were predominantly pharmacokinetic (modified absorption, 35%); potential NHP-NHP interactions were mostly pharmacodynamic (increased risk of bleeding, 47%).

Medications are used concurrently with NHP in every fifth pediatric patient in the emergency department and many NHP users are receiving more than 1 NHP simultaneously. One quarter of all paired medication-NHP or NHP-NHP could potentially cause interactions. Although we can not confirm that these were true interactions resulting in clinical symptoms, parents and health care providers need to balance the potential benefit of concurrent NHP-medication use with its potential harms.