The Health Sciences Authority (HSA), in consultation with its Medicines Advisory Committee, granted interim authorisation under the Pandemic Special Access Route (PSAR) for Pfizer’s Paxlovid, a combination of two medicines, nirmatrelvir (the antiviral medicine) and ritonavir (to maintain the blood level of nirmatrelvir for antiviral efficacy).
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This is the first oral tablet approved in Singapore for the treatment of mild to moderate COVID-19 in adult patients who are at high risk of progression to severe disease, to reduce the risk of hospitalisation and death.
Paxlovid is to be taken twice daily for 5 days, and the treatment should be initiated as soon as possible after a diagnosis has been made, within 5 days of the onset of COVID-19 symptoms. It will be prescribed and prioritised to those at higher risk of severe COVID illness, as directed by the Ministry of Health.
HSA’s review of the available clinical data based on rolling submission of the results from an ongoing Phase II/III study found that Paxlovid reduced the risk of COVID-19 related hospitalisation or death as compared to the placebo group by 88.9% when treatment was given within 3 days of onset of symptoms and 87.8% when given within 5 days of onset of symptoms.
The efficacy analysis included patients infected with the Delta variant. In vitro data has shown that Paxlovid is active against the prevailing variants of concern, including the Delta and Omicron variants.
The randomised, placebo-controlled study recruited more than 2,000 participants aged 18 to 88 years with mild to moderate COVID-19 and who had one or more risk factors for progression to severe COVID-19. 1,039 participants received Paxlovid and 1,046 received placebo.
The results showed that 0.8% (8 / 1,039) of patients who received Paxlovid and 6.3 % (66 / 1,046) of those who received placebo were hospitalised. There was no death in the PAXLOVIDTM arm, compared to 12 deaths in the placebo arm.
The safety data showed that Paxlovid is wellâ€tolerated. The incidences of adverse events reported in the clinical study were generally low. The common adverse events reported were mild to moderate, such as altered sense of taste, diarrhoea, vomiting, hypertension, muscle pain (myalgia) and chills.
Paxlovid may interact with various medications, such as medicines for irregular heart rate, migraine, cholesterol, etc., and could increase the amount of these medications in the blood, leading to serious adverse events.
On the other hand, some medicines such as those for epileptic seizures could reduce the levels of Paxlovid resulting in a loss of anti-viral efficacy. The potential for drug interactions should be carefully considered by the prescribing doctor prior to treatment initiation.
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. ■