SINGAPORE — The Health Sciences Authority (HSA) has granted interim authorisation on Monday (Jan 31) for Paxlovid, a drug by biopharmaceutical firm Pfizer, to be used to treat mild to moderate Covid-19 in adults. 

This is the first oral medicine approved in Singapore for the treatment of the Sars-CoV-2 coronavirus, HSA said in a release on Thursday. 

It will be prescribed to and prioritised for patients at higher risk of severe Covid-19, as directed by the Ministry of Health. 

Previously, HSA authorised the use of other treatments for Covid-19 including Casirivimab and Imdevimab by Roche-Regeneron and Sotrovimab by GlaxoSmithKline, which are administered intravenously. 

Paxlovid should be taken orally twice daily for five days and the treatment should be initiated as soon as possible after a diagnosis has been made, within five days of the onset of Covid-19 symptoms, HSA said. 

It added that based on available clinical data from an ongoing study, the medication was found to reduce the risk of Covid-19-related hospitalisation or death by 88.9 per cent when treatment was given within three days of the onset of symptoms, and by 87.8 per cent when given within five days of the onset of symptoms.   

It is also reported to be effective against the Delta and Omicron virus strains. 

The study included more than 2,000 participants aged between 18 and 88 who had mild to moderate illness and who had one or more risk factors for progression to severe Covid-19. 

The results found that 0.8 per cent of the 1,039 participants who were given Paxlovid were hospitalised compared to 6.3 per cent of the 1,046 participants who were given a placebo. 

There were also no deaths among those given Paxlovid compared to 12 deaths among those who received the placebo. 

HSA said the data also showed that Paxlovid is "well-tolerated" and that incidences of adverse events or side effects reported in the clinical study were "generally low".

The common adverse events reported were mild to moderate such as an altered sense of taste, diarrhoea, vomiting, hypertension, muscle pain (myalgia) and chills.

However, it cautioned that Paxlovid may interact with certain medications such as those that are used to treat migraines, irregular heart rates and cholesterol — by increasing the amount of these medications in the blood, leading to serious adverse events. 

Conversely, there are medications that may also reduce the levels of Paxlovid resulting in the loss of anti-viral efficacy. 

"The potential for drug interactions should be carefully considered by the prescribing doctor prior to treatment initiation," HSA said. 

“Based on the available clinical evidence, the benefits of Paxlovid outweigh the risks, and there is a favourable benefit-risk profile for the treatment of mild to moderate Covid-19 in adults who are at high risk of progression to severe Covid-19."

As HSA has granted Paxlovid interim authorisation under the Pandemic Special Access Route to facilitate early access to critical medicines during a pandemic, Pfizer is required to continue submitting updated data from ongoing clinical studies to ensure the continued safety and efficacy of Paxlovid, such as its efficacy against prevailing virus variants. 

"HSA will actively review the data submitted by Pfizer to ensure that the benefits of Paxlovid continue to outweigh the known risks," it said.