CANADA TOUGHENS ANTIHISTAMINES STANCE

The Health Protection Branch of Canada has switched two antihistamine products, Marion Merrell Dow's Seldane (terfenadine) and Janssen's Hismanal (astemizole) to "behind-the-counter status," following reports of adverse reactions to this class of drugs (Marketletters passim). The products have been linked to potentially serious cardiac complications if taken in overdose or with certain other drugs in the case of Seldane.

The HPB has also tightened warnings on the labelling of the two products to draw attention to the possible dangers. There have been no deaths linked to either Seldane or Hismanal in Canada. The agency has also required that the companies send out "Dear Doctor" and "Dear Pharmacist" letters informing of the change in status. Following on, the Food and Drug Administration in the USA has now mandated similar labelling changes for Hismanal.

The restrictions imposed on Seldane in the USA may delay the approval of over-the-counter versions of Hismanal and Schering-Plough's Claritin (loratadine) pending FDA review of the possibility of adverse reaction problems, according to Hemant Shah of HKS & Co. Mr Shah believes that the FDA is likely to wait for at least a year, to ensure that there are no further adverse reactions to Seldane after the tightening of the labelling restrictions.