The Department of Health today (March 20) alerted clients of a listed Chinese medicine practitioner, Yim Hing-yan, practising at On Tai Tong Medicine Co. in Yau Ma Tei, that if they have been supplied with a yellowish powder, they should stop using it and then either contact the practitioner or consult other healthcare professionals for advice because the powder was found to contain two undeclared western drugs, namely prednisone and chlorpheniramine.   Close