COVID-19 Antiviral Therapies

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COVID-19 Antiviral Therapies

CPS understands the continued gravity of the COVID-19 pandemic. As the situation evolves, we are constantly updating the tools and resources that we provide to leaders at our managed pharmacy locations.

The U.S. Food and Drug Administration has issued Emergency Use Authorization for two oral antivirals for the treatment of mild to moderate COVID-19 in adults with positive results of direct SARS-CoV-2 viral testing who are at high risk for progression to severe COVID-19, including hospitalization or death, and for whom alternative COVID-19 treatment options authorized by the FDA are not accessible or clinically appropriate.

In this blog, we’ll take a look at these two medications:
  • Nirmatrelvir/ritonavir (Paxlovid™),(Pfizer)
  • Molnupiravir (Merck)

While these two medications are expected to be important tools in the fight against the virus, neither medication is a substitute for vaccination in individuals for whom COVID-19 vaccination and a booster dose are recommended. Both are prescription oral antivirals that can be taken in the home setting and do not require infusion for administration as opposed to remdesivir and monoclonal antibodies.

Nirmatrelvir/ritonavir (Paxlovid)

Nirmatrelvir/ritonavir has been authorized for patients 12 years of age and up with mild to moderate COVID-19 who are most likely to progress to severe disease. It should be prescribed and administered as soon as possible after diagnosis and within five days of symptom onset.1 The treatment is administered in two 150-milligram tablets of nirmatrelvir along with one 100-milligram tablet of ritonavir per dose. All three tablets are taken together twice daily for five days. The dose of the medication must be adjusted for those with renal impairment (eGFR less than 60 mL/min), and it is not recommended for those with eGFR less than 30 mL/min.

Drug interactions:
Use of ritonavir may reduce the efficacy of combined hormonal contraceptives. Advise patients using combined hormonal contraceptives to use an effective alternative contraceptive method or an additional barrier method of contraception. Ritonavir may also interact with many other medications, resulting in increased or decreased serum concentrations.

Adverse effects:
Most common adverse reactions (≥1% of subjects) in nirmatrelvir/ritonavir vs. placebo respectively: dysgeusia (6% and <1%), diarrhea (3% and 2%), hypertension (1% and <1%), and myalgia (1% and <1%)

Who should not take Paxlovid:
  • Patients with severe renal impairment (eGFR <30mL/min)
  • Patients with severe hepatic impairment (Child-Pugh Class C)

*Patients on cobicistat and ritonavir products; continue as indicated with no dose adjustments.


Molnupiravir should be initiated as soon as possible after diagnosis of COVID-19 and within five days of symptom onset. Dosing recommendations are 800 mg (four 200mg capsules) orally twice daily for five days. The doses may be taken with or without food. No dose adjustments are necessary based on age or on renal or hepatic impairment. Molnupiravir is not authorized for the pre-exposure or post-exposure prevention of COVID-19 or for initiation of treatment in patients hospitalized due to COVID-19, because benefit of treatment has not been observed in people when treatment is started after hospitalization due to COVID-19.2

Drug interactions:
No drug interactions have been identified to date.

Adverse effects:
The most common adverse reactions reported (≥1% of subjects) during treatment and during 14 days after the last dose included diarrhea (2%), nausea (1%), dizziness (1%), and headache (1%), all of which were Grade 1 (mild) or Grade 2 (moderate). It is important not to open, break, or crush the capsules.

Who should not take molnupiravir:
  • Patients younger than 18 years of age, because it may affect bone and cartilage growth
  • Patients who are pregnant
More detail on these medications can be found in this chart.

For more information and insights on how CPS can help your hospital or health system address COVID-related challenges, contact us: contactus@cpspharm.com.

1 https://www.cnbc.com/2021/12/22/fda-authorizes-pfizers-covid-treatment-pill-the-first-oral-antiviral-drug-cleared-during-the-pandemic.html. Accessed 1.06.22

2 https://www.fda.gov/news-events/press-announcements/coronavirus-covid-19-update-fda-authorizes-additional-oral-antiviral-treatment-covid-19-certain. Accessed 1.06.22.

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