Japan Approves Pfizer Covid-19 Oral Pill Amid Surging Omicron Infections: All About The Drug

Clinical trials have shown that Pfizer's Covid-19 oral pill Paxlovid can reduce the risk of COVID-19 related hospitalization or death by 88 per cent compared to placebo when given within five days of symptom onset.

Keeping in view the surge of coronavirus cases driven by the highly transmissible Omicron variant, Japan's health ministry has granted fast-track approval to Pfizer's oral COVID-19 pill for treatment of mild infections.

Paxlovid, which is a combination of the antiviral drugs nirmatrelvir and ritonavir, is the second oral drug the country has approved for use in patients with mild symptoms. In December, Japan had approved molnupiravir, the oral drug developed by U.S. pharmaceutical company Merck & Co.

Health minister Shigeyuki Goto told reporters on Thursday that their government has inked an agreement with Pfizer to procure Paxlovid for 2 million people within the year, of which pills for 40,000 people have already arrived.

The drug would be distributed to medical institutions by as early as Monday the health minister said, adding that additional deliveries would be made later this month.

Know more about Pfizer's Paxlovid

Pfizer's Paxlovid contains nirmatrelvir and ritonavir tablets. While nirmatrelvir prevents SARS-CoV-2 from replicating by inhibiting a viral protein, ritonavir slows down nirmatrelvir's breakdown so that it remains in the body for a longer period at higher concentrations. Paxlovid is administered as three tablets (two tablets of nirmatrelvir and one tablet of ritonavir taken together orally) twice a day for five days, which means a total of 30 tablets. The drug is not recommended for use for longer than five consecutive days.

The U.S. Food and Drug Administration (FDA) authorised the use of Paxlovid for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (12 years of age and older) on December 22, 2021. It had stated that Paxlovid should be initiated as soon as possible after diagnosis of COVID-19 and within five days of symptom onset. The pill has been approved in Britain too.

Possible side effects of Paxlovid

The U.S. FDA cautioned that Paxlovid should not be used for the pre-exposure or post-exposure prevention of COVID-19. It is also not authored for initiation of treatment in those requiring hospitalization due to severe or critical COVID-19. Paxlovid is not a substitute for vaccination, it said.

Paxlovid may cause side effects such as impaired sense of taste, diarrhea, high blood pressure and muscle aches. Using Paxlovid at the same time with certain other drugs may result in potentially significant drug interactions, FDA warned.

The drug is not recommended for patients with severe kidney or severe liver impairment. In people with uncontrolled or undiagnosed HIV-1 infection, Paxlovid use may lead to HIV-1 drug resistance. When giving the pill to patients with preexisting liver diseases, liver enzyme abnormalities or liver inflammation, caution should be exercised as ritonavir may cause liver damage, experts said.

Japan's Health Minister Shigeyuki Goto also noted that ritonavir cannot be taken simultaneously with a high blood pressure drug and many other kinds of medications.

Considering the potential side effects, the pill would initially be prescribed in 2,000 medical institutions in Japan until Feb. 27. Based on the results of the trial period, permission may be given to other hospitals and pharmacies to prescribe the drug from Feb. 28, Goto said.

According to Pfizer, clinical trials have shown that Paxlovid can reduce the risk of hospitalizations and deaths by 88 per cent in patients who took the drug within five days of the onset of symptoms compared with those who took a placebo. It is claimed that Paxlovid is more effective than molnupiravir.