EXTENDING the shelf-life of a drug is not a rare occurrence. Pharmaceutical companies routinely ask for this, backing their applications with scientific data that is counter-checked by regulatory bodies.

The Health Sciences Authority (HSA) approves 20 to 30 such applications yearly, including an extension for the anti-viral drug Tamiflu.

Roche, the manufacturer of the drug, had asked that two more years be added to the five-year shelf-life of the drug in July last year. The HSA okayed the application after checks against the manufacturer's data to ensure that the drug would be as potent as ever.

Even with an extension to seven years, the potency levels of Tamiflu were found to be between 90 per cent and 105 per cent, said Dr Lim Poh Lian, senior consultant at the Communicable Diseases Centre (CDC).

'As a clinician, there is no way I will be giving medication to my patients if I knew it was ineffective,' she said.

She was responding to doctors who had misgivings about the extended shelf-life of the drug, intended to combat those with the H1N1 flu.

Roche has specified that all stocks have to be stored at below 25 deg C and kept in a dry place with a humidity level of about 60 per cent. The Health Ministry said that the Government's Tamiflu stockpile is stored in an air-conditioned environment, where temperatures and humidity levels are monitored hourly.

Ministry officials were also asked about Tamiflu meant for commercial supply, which had its shelf-life similarly extended on June 18 this year. Did they meet quality conditions as well given that there could be temperature changes in storage?

The ministry said that Roche had also provided data at higher temperatures of 30 deg C for 36 months and 40 deg C for six months 'which will address the issues on short-term temperature spikes that occur'.

Dr Lee Yik Voon, a general practitioner in Circuit Road who had previously worked in a pharmaceutical company, said it was common for drug companies to test the efficacy of a drug often to see if its shelf-life could be extended.

Read the full story in Friday's edition of The Straits Times.