Three versions of a diabetes medication are being recalled here after they were found to contain unsafe levels of an impurity that could potentially cause cancer.
The Health Sciences Authority (HSA) tested all 46 locally marketed metformin medicine. Of these, 43 are not affected.
The HSA said on Wednesday that three metformin drugs were found to contain a type of nitrosamine, N-nitrosodimethylamine (NDMA), in trace amounts that are above the internationally acceptable level.
NDMAs are classified as potential carcinogens for humans.
As a precaution, the HSA said it is recalling the three affected drugs, which are used to control high blood sugar levels in diabetic patients.
The recalled drugs are: one batch of the Glucient XR 500mg tablet, supplied by Glorious Dexa Singapore; and all batches of Meijumet prolonged-release tablet in 750mg and 1,000mg versions, supplied by Pharmazen Medicals.
The HSA said the risk to patients who have been taking the affected medicine is "very low". This is because the cancer risk of nitrosamines is associated with long-term use of the affected drugs, and the medicine has been supplied here for only a short period of time - since last year.
Patients taking the affected metformin medicine are advised not to stop treatment on their own, as doing so suddenly will raise blood sugar levels, which may pose a greater health risk than the trace amounts of NDMA.
The HSA has also advised healthcare professionals to contact their patients who are taking the affected drugs and arrange for an exchange of their medicine as soon as possible.
Patients who are concerned about their current treatment should speak to their doctor or pharmacist.
NDMA can be found in low levels in processed food - including pickled vegetables, salted fish, processed meat products such as bacon and sausages - and in polluted air.
Worldwide recalls were recently done when NDMA was found to be formed unexpectedly during the manufacture of some medicines, including some heart and gastric drugs.
The internationally acceptable level of NDMA is 96 nanograms per day. This is the amount deemed reasonably safe if a patient takes the affected medicine every day continuously for a lifetime of 70 years.
On Wednesday, the United States Food and Drug Administration said that it is testing samples of metformin sold in the US for NDMA and will recommend recalls as appropriate, Bloomberg reported.
The European Medicines Agency has also asked companies to test for high levels of NDMA in metformin. No dangerous levels have been detected in European Union supplies to date.
The HSA is working with the companies supplying the affected medicine and international regulatory agencies to verify the causes of the contamination, and identify the measures to address the issue.
Consumers can contact the HSA on 6866-3538 or e-mail firstname.lastname@example.org if they have more questions.