After the scandal broke in Germany in late November 1961, drug companies Merrell and Horner sent out simple letters to Canadian doctors with the recommendation to not prescribe Thalidomide to pregnant women any more. It is unclear how many doctors received those letters and if they all actually read them. In late February 1962 Times Magazine reported that Thalidomide was still available in Canada. After other media outlets picked up the story, the Canadian Food and Drug Directorate finally decided to act.
Source: Michael Magazanik: Silent Shock. The Men behind the Thalidomide Scandal and an Australian Family’s Long Road to Justice. Melbourne 2015, pp. 164f.