Evaluation of a Web-Based, 'Purchase Event' Intensive Monitoring Method for Pharmacovigilance of Natural Health Products: Lessons and Insights from Development Work in New Zealand.

These web-based, purchase event, intensive monitoring studies, with cohorts built through NHP purchases in pharmacies, identified substantial issues with recruiting pharmacists/pharmacies and NHP purchasers that, at present, render such studies unfeasible. Future studies need to consider other methods of recruiting NHP purchasers and develop a simple method for recording NHP purchases.