More than half of the patients affected by the recall of three brands of high blood pressure medicine containing losartan have switched to alternatives.
The remaining patients are expected to receive safer medicine by the end of next month, Senior Minister of State for Health Lam Pin Min told Parliament yesterday.
He said stocks of losartan that have been found to be safe, as well as other high blood pressure medicines in the same class, are expected to stabilise by July 1.
"We would like to reassure all patients that we have sufficient stocks of alternatives, as well as losartan that is not contaminated with nitrosamines," said Dr Lam.
The Health Sciences Authority (HSA) had recalled 50mg and 100mg tablets from Hyperten, Losagen and Losartas in March after they were found to contain higher than acceptable levels of a nitrosamine impurity.
The Ministry of Health (MOH) said then that about 137,000 patients in Singapore were using the recalled brands. Another seven brands of losartan medicines sold here were not affected.
Exposure to nitrosamines at higher quantities over a long-term period may potentially increase the risk of cancer.
Dr Lam said the immediate health risk posed by the impurity was assessed to be low and that patients who had been prescribed the affected brands should continue taking their medicine, as stopping could pose a greater health risk.
He was replying to Nominated MP Irene Quay, who had asked about HSA's drug testing process and the steps taken by MOH in response to the recall.
Dr Lam said the HSA's standards, checks and processes are similar to those adopted by regulatory bodies in Australia, Canada, Europe, Japan and the United States, and that generic medicines are subjected to the same regulations.
"The routine tests required of the manufacturers are based on known impurities that may be generated during the manufacturing process, as it is not practical to exhaustively test for all types of impurities," he said.
In the case of losartan, the required tests had not included checking for nitrosamines, as such impurities were not expected to be generated, Dr Lam said, adding that this approach is similar to those adopted by the US, Canada and Europe.
Since the recall, the HSA has been working with suppliers and international regulators to determine the cause of contamination and to formulate measures to eliminate the nitrosamines in the medium to long term.
"HSA will continue to monitor the quality and safety of these medicines to safeguard public health," said Dr Lam.