As the new variant of covid-19 affects every country in the world, the need for emergency drugs that offer safe protection has become vital. In this regard, several people have been prescribed antiviral pills from Pfizer and Merck in the hope of immunizing themselves against covid-19. However, such prescriptions can have the opposite effect to that expected, according to experts.

The US drug regulatory agency Food and Drug Administration (FDA) has authorized the administration of Pfizer's Paxlovid for mild or moderate covid in young people and people around 12 years old because they have major underlying conditions that increase the risk of hospitalization or death due to coronavirus. This medication the FDA does not recommend people with severe kidney or liver problems.

Due to concerns about the potential side effects of Merck's molnupiravir, the FDA has restricted its use to adults and only in scenarios where other authorized treatments, including monoclonal antibodies, are unaffordable or not "clinically appropriate."

The Paxlovid cocktail consists of two tablets of the antiviral nirmatrelvir and one tablet of ritonavir, a drug that has long been used as what is known as a booster agent in HIV treatments. Ritonavir suppresses a key enzyme in the liver called CYP3A, which metabolizes many drugs, including nirmatrelvir. In the case of Paxlovid treatment, ritonavir slows the breakdown of the active antiviral in the body and helps it remain at a therapeutic level for longer.

When Paxlovid is combined with other drugs that are also metabolized by the CYP3A enzyme, the main concern is that the ritonavir component may boost the co-administered drugs to toxic levels.

Complicating matters, drugs that pose interaction risks are widely prescribed to people at higher risk of covid due to other health conditions.

Medications include, but are not limited to: anticoagulants; anticonvulsant medications; medications for irregular heart rhythms, high blood pressure, and high cholesterol; antidepressants and anti-anxiety medications; immunosuppressants; steroids (including inhalers); HIV treatments; and medications for erectile dysfunction.

"Some of these potential interactions are not superficial, and some combinations have to be avoided altogether," said Peter Anderson, professor of pharmaceutical sciences at the University of Colorado Anschutz Medical Campus. "Some are probably easily managed. But some we're going to have to be very careful."

Even with concerns about taking Paxlovid with other prescription drugs, experts are excited about the drug's potential.

"Paxlovid is a revolutionary drug," Anderson said. "This could make a real difference in the pandemic by making an effective covid treatment available to many people."