SINGAPORE - A drug prescribed to smokers to help them quit the habit has been suspended from distribution in Singapore after cancer-causing agents called nitrosamines were found in the pills.
Responding to queries from The Straits Times, the Health Sciences Authority (HSA) on Wednesday (Oct 6) said it was alerted in May to the presence of nitrosamine impurities in Champix by drug manufacturer Pfizer.
Pfizer had suspended local distribution in June as a precautionary measure, said HSA, adding that the potential risk of nitrosamines has been associated with long-term exposure.
"The potential risk to patients is low, as patients who are prescribed Champix would generally be given the medicine on a short-term basis," said HSA.
It is usually prescribed for a short-term period of up to 24 weeks, the authority said.
HSA advises patients already on Champix to continue taking their medication as prescribed by their doctors, as stopping the medicine abruptly may disrupt the programme they are on to quit smoking.
"Patients are encouraged to consult their doctors if they have any concerns relating to the use of Champix tablets or if there may be a need to change to an alternative therapy," said the authority.
Alternatives include nicotine-replacement therapies in the form of chewable gum, lozenges and patches. These are available at the pharmacies or from a doctor, it added.
The authority also said it is reviewing and working with Pfizer on the impurities and will provide updates if there are new findings.
"As this is a newly discovered nitrosamine impurity, there is continuing review on the acceptable limit of this impurity among international regulators and the company," said HSA.
"Nitrosamines were not expected to be generated during manufacturing and, hence, testing for them routinely was previously not part of the testing parameters.
"As part of the regulatory approach to manage the evolving issue of nitrosamine contamination, companies are required to test new batches of products for the impurities if they have been assessed to be at risk of contamination," said HSA.
It added that this approach is similar to that adopted in the United States, Canada and the European Union.
Separately, Pfizer had announced last month that it was recalling all lots of the medicine in the US.