Here’s what we know about FDA-authorized COVID-19 antivirals

COVID-19 Antivirals

Loren Bonner

While FDA has authorized two COVID-19 antiviral medications—Paxlovid from Pfizer and molnupiravir from Merck, Americans may not have the easiest time accessing these medications, which are aimed at preventing hospitalizations and deaths in high-risk patients.

At press time, Paxlovid and molnupiravir will only be available in a limited number of pharmacies. Patients will need a prescription from specific licensed health care providers to get the medications.

While PREP Act authority allows pharmacists to order and dispense COVID-19 therapeutics, including oral and subcutaneous medication, FDA specifically prevents pharmacists from writing prescriptions for these anti-virals. In a press statement, APhA noted that oral antivirals are most effective when taken early in a COVID-19 infection. “Requiring patients to make an appointment with another prescriber just to get a prescription that their pharmacist will fill adds time, cost, and inconvenience but most concerning of all, it could cause hospitalizations and even deaths.

The ability of pharmacies to be a one-stop-shop for testing, patient assessment, ordering, and dispensing would be a game-changer for timely access to these needed treatments—just as it has been for the administration of COVID vaccines,” stated APhA.

Information for clinicians

In late December 2021, FDA issued an EUA for the Pfizer and Merck oral antiviral medications to treat patients with mild to moderate COVID-19 at risk of progression to severe infection. Neither medication is authorized for pre- or postexposure prophylaxis, nor should it be used to treat patients with severe COVID-19, including patients who have been hospitalized.

Both medications should be started as soon as possible after a COVID-19 diagnosis and within 5 days of symptom onset. See the chart below on how the two oral antivirals compare. Pfizer’s Paxlovid is dosed as two nirmatrelvir 150 mg tablets and one 100 mg ritonavir tablet by mouth, twice daily, for 5 days. Nirmatrelvir inhibits SARS-CoV-2 replication while ritonavir works by slowing the breakdown of nirmatrelvir. Paxlovid is authorized for use in patients 12 years and older who weigh at least 40 kg and have received a positive COVID-19 diagnosis.
Dosing is decreased in patients with compromised renal function and there are drug–drug interactions to avoid.

Merck’s molnupiravir is supplied as a 200 mg oral capsule. It is dosed as 4 capsules by mouth, twice daily, for 5 days. Molnupiravir works by introducing errors into the SARS-CoV-2 genetic code. It is only authorized for patients 18 years and older because it may also inhibit bone and cartilage growth.

Molnupiravir is for patients for whom alternative COVID-19 treatment options authorized by FDA are not accessible or clinically appropriate. Similar drugs are also in the pipeline that could have positive safety and efficacy profiles (see table above). ■

ISMP issues warning about possible medication safety issues with newly authorized antiviral

To encourage the appropriate use of Pfizer’s COVID-19 antiviral drug nirmatrelvir/ritonavir (Paxlovid), the Institute for Safe Medication Practices (ISMP) released an alert for dispensing pharmacists.

ISMP stated that a dose reduction is necessary for patients with moderate renal impairment, and patients with severe renal impairment should not receive the drug.

Paxlovid, which received an EUA from the federal government, is designed to treat patients with positive COVID-19 viral testing results and who are at high risk for progression to severe disease.

The drug is only available in a carton containing 5 blister cards, each with daily morning and evening doses comprising two tablets of nirmatrelvir and one tablet of ritonavir. For patients with moderate renal impairment, pharmacists should remove one of the nirmatrelvir tablets for both the morning and evening doses from each blister card before being dispensed. The empty blisters on all 5 cards should be covered with manufacturer-supplied stickers.

ISMP said other possible safety issues include drug–drug interactions and patients failing to take both tablets together. Providers should report errors with the medication within their health care organizations and to FDA’s MedWatch reporting program, which is mandatory for products under an EUA. ISMP also requests providers report medication errors to its medication error reporting program.