Covid – 19

Paxlovid is a Complicated Drug. Here’s a look at the Structural Formula of its components.

Structure of Nirmatrelvir
Structure of Ritonavir

Understanding the Covid Wonder Drug – Paxlovid

Paxlovid is a drug made by Pfizer and has received emergency use authorization.   It is provided FREE to patients upon prescription by a physician.  However, it is not without risks, mostly because of how it works.   The human body has a way of getting rid of medications after you take them.  One of the drugs in Paxlovid, ritonavir, keeps the active Nirmatrelvir in your system longer so it can do a better job fighting Covid for you.  However, this poses a potential risk as other medications you may be taking are affected.  That is why it is so important to take Paxlovid only in consultation with  your doctor and to carefully follow all directions.

What is Paxlovid?

PAXLOVID is nirmatrelvir tablets co-packed with ritonavir tablets.  Nirmatrelvir is a SARS-CoV-2 main protease (Mpro) inhibitor, and ritonavir is an HIV-1 protease inhibitor and CYP3A inhibitor.  The packaging consists of 5 blister packs, each containing a morning 3 tablet dose and an evening 3 tablet dose. The molecular formula of Nirmatrelvir is C23H32F3N504 with a molecular weight of 499.54.  Each tablet contains 150 mg nirmatrelvir. The molecular formula of Ritonavir is C37H48N605S2 with a molecular weight of 720.95.  Each tablet contains 100mg of ritonavir.

How Does the Medicine Work?

Nirmatrelvir is a peptidomemetic inhibitor of the SARS-CoV-2 main protease (Mpro), also referred to as 3C-like protease (3CLpro) or nsp5 protease.  Inhibition of SARS-CoV-2 Mpro renders it incapable of processing polyprotein precursors, preventing viral replication.   How do they know this?   They used X-ray crystallography to determine that Nirmatrelvir was found to bind directly to the SARS-CoV2 Mpro active site.

What does Ritonavir Do?

The other drug in Paxlovid is, Ritonavir.  Ritonavir is an HIV-1 protease inhibitor but is not active against SARS-CoV-2 Mpro.  Ritonavir inhibits the CYP3A-mediated metabolism of nirmatrelvir, resulting in increased plasma concentrations of nirmatrelvir.   In other words, you get a higher concentration in your blood of the active drug to make it work better.  However, this function means higher concentrations of other drugs  you make take may occur – therefore the need to work with your doctor and to proceed cautiously with anything you take while on this medicine, and in some cases, lower dosages or stop certain medications, even before or after  you take Paxlovid.

FDA Info was updated July 6, 2022

The FDA just put out a revision on this drug on July 6, 2022. It has only been evaluated in adults.  However, The FDA has authorized the emergency use of PAXLOVID for the treatment of mild-to-moderate COVID-19 in adults and children [12 years of age and older weighing at least 88 pounds (40 kg)] with a positive test for the virus that causes COVID-19, and who are at high risk for progression to severe COVID-19, including hospitalization or death, under an EUA. 

Prevention of Hospitalization and Death

Included in this documentation was the following comparisons to adults taking a placebo. Hospitalization: Taking Paxlovid – .8%, Placebo – 6.3%.    All-cause mortality through Day 28 found no deaths among those taking Paxlovid with a mortality rate of 1.1% in those taking a Placebo.

More information: Visit this website.

We also have the Complete Fact Sheet on Paxlovid for Health Providers released by FDA on July 6, 2022. CLICK HERE.

We have the patient info guide for Patients, Parents, and Caregivers. CLICK HERE.

Massachusetts Covid Dashboard (Data as of July 7, 2022)

Covid is still around. Average age of patients dying from the disease is 83.

Massachusetts Covid Dashboard
Percent Positivity Map

Positivity Rate in Gardner MA is currently about half the state average.

Positivity Rates in the Area:

Gardner:  3.21%,  Templeton: 3.37&, Winchendon: 2.78%, Ashburnham: 4.76%, Hubbardston: 3.36%, Westminster: 2.99%.  Nearby Ashby is just under 1%. 

In contrast, Boston’s positivity rate is 6.46%, Edgartown is 21.23%, Fitchburg is 2.97%, Leominster is 4.41%, Worcester is 4.07%, and Springfield is 6.2%