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Frequently Asked Questions1About PaxlovidWho can be treated with PAXLOVID?

PAXLOVID is indicated for the treatment of COVID-19 in adults who do not require supplemental oxygen and who are at increased risk for progressing to severe COVID-19.1

For more information about who is at increased risk for progressing to severe COVID-19, see Section 5.1: Pharmacodynamic properties of the SmPC [here].

Which patients* are considered to be at risk of progressing to severe COVID-19?         
National guidelines may differ from the approved indications. 

Any of the following risk factors can put a patient at risk for progressing to severe COVID-19:

  • Diabetes
  • Overweight (BMI >25)
  • Chronic lung disease (including asthma)
  • Chronic kidney disease**
  • Current smoker
  • Immunosuppressive disease or treatment
  • Cardiovascular disease
  • Hypertension 
  • Sickle cell disease
  • Neurodevelopmental disorders
  • Active cancer
  • Medically related technological dependence 
  • 60 years of age and older, regardless of comorbidities


*Patients is defined as adults who do not require supplemental oxygen and who are at increased risk of progressing to severe disease.1

**In patients with moderate renal impairment (eGFR ≥ 30 to < 60 mL/min), the dose of Paxlovid should be reduced to nirmatrelvir/ritonavir 150 mg/100 mg every 12 hours for 5 days to avoid over-exposure (this dose adjustment has not been clinically tested). Paxlovid should not be used in patients with severe renal impairment [eGFR < 30 mL/min, including patients with End Stage Renal Disease (ESRD) under haemodialysis]. 

For more information about risk factors for progression to severe disease, see Section 5.1: Pharmacodynamic properties of the SmPC [here]

Is PAXLOVID appropriate for paediatric patients?

PAXLOVID has been granted full marketing authorisation for the treatment of COVID-19 in adults who do not require supplemental oxygen and who are at increased risk for progressing to severe disease.

PAXLOVID is not authorised for use in paediatric patients. The safety and efficacy of PAXLOVID in patients below 18 years of age have not been established. No data are available.1

What is PAXLOVID? 

Paxlovid is an antiviral medicine with a combination of active ingredients, nirmatrelvir and ritonavir, that works by inhibiting a protease required for virus replication.2

How is Paxlovid used?

For oral use.

Nirmatrelvir must be coadministered with ritonavir. Failure to correctly coadminister nirmatrevlir with ritonavir will result in plasma levels of this active substance that will be insufficient to achieve the desired therapeutic effect. PAXLOVID can be taken with or without food. The tablets should be swallowed whole and not chewed, broken, or crushed.1

For more information, see Section 4.2: Posology and method of administration of the SmPC [here]

How does PAXLOVID work? 

Nirmatrelvir is a peptidomimetic inhibitor of the SARS-CoV-2 main protease (Mpro), also known as 3-chymotrypsin-like cysteine (3CL) protease enzyme. Inhibition of the SARS-CoV-2 Mpro renders the protein incapable of processing polyprotein precursors, which leads to the prevention of viral replication.                                                                                      

Ritonavir inhibits the CYP3A-mediated metabolism of nirmatrelvir, thereby providing increased plasma concentrations of nirmatrelvir.                                                                                                                                                                                                        
For more information about how PAXLOVID works and its antiviral activity, see Section 5.1: Pharmacodynamic properties of the SmPC [here]

Why is Nirmatrelvir coadministered with ritonavir?

Ritonavir is administered with nirmatrelvir as a pharmacokinetic enhancer resulting in higher systemic concentrations of nirmatrelvir. Upon repeat-dose of nirmatrelvir/ritonavir 75 mg/100 mg, 250 mg/100 mg, and 500 mg/100 mg administered twice daily, the increase in systemic exposure at steady-state appears to be less than dose proportional. Multiple dosing over 10 days achieved steady-state on Day 2 with approximately two-fold accumulation. Systemic exposures on Day 5 were similar to Day 10 across all doses.1

For more information about ritonavir, see Section 5.2: Pharmacokinetic properties of the SmPC [here].

What are the results of the clinical trial on high-risk COVID-19 patients treated with PAXLOVID?

The efficacy of Paxlovid is based on the interim analysis and the supporting final analysis of EPIC‑HR, a phase 2/3, randomised, double-blind, placebo-controlled study in non‑hospitalised, symptomatic adult participants with a laboratory confirmed diagnosis of SARS-CoV-2 infection. Eligible participants were 18 years of age and older with at least 1 of the following risk factors for progression to severe disease: diabetes, overweight (BMI > 25 kg/m2), chronic lung disease (including asthma), chronic kidney disease, current smoker, immunosuppressive disease or immunosuppressive treatment, cardiovascular disease, hypertension, sickle cell disease, neurodevelopmental disorders, active cancer, medically‑related technological dependence, or were 60 years of age and older regardless of comorbidities. Participants with COVID-19 symptom onset of ≤ 5 days were included in the study. The study excluded individuals with a history of prior COVID-19 infection or vaccination.

Participants were randomised (1:1) to receive Paxlovid (nirmatrelvir/ritonavir 300 mg/100 mg) or placebo orally every 12 hours for 5 days. The primary efficacy endpoint was the proportion of participants with COVID‑19 related hospitalisation or death from any cause through Day 28. The analysis was conducted in the modified intent-to-treat (mITT) analysis set (all treated participants with onset of symptoms ≤ 3 days who at baseline did not receive nor were expected to receive COVID-19 therapeutic mAb treatment), the mITT1 analysis set (all treated participants with onset of symptoms ≤ 5 days who at baseline did not receive nor were expected to receive COVID-19 therapeutic mAb treatment), and the mITT2 analysis set (all treated participants with onset of symptoms ≤ 5 days).

A total of 2113 participants were randomised to receive either Paxlovid or placebo. At baseline, mean age was 45 years with 12% of participants 65 years of age and older (3% were 75 years of age and older); 51% were male; 71% were White, 4% were Black or African American, and 15% were Asian; 41% were Hispanic or Latino; 67% of participants had onset of symptoms ≤ 3 days before initiation of study treatment; 80% had a BMI > 25 kg/m2 (36% a BMI > 30 kg/m2); 11% had diabetes mellitus; less than 1% of the study population had immune deficiency, 49% of participants were serological negative at baseline and 49% were serological positive. The mean (SD) baseline viral load was 4.71 log10 copies/mL (2.89); 27% of participants had a baseline viral load of > 10^7 (copies/mL); 6.0% of participants either received or were expected to receive COVID-19 therapeutic mAb treatment at the time of randomisation and were excluded from the mITT and mITT1 analyses. The primary SARS-CoV-2 variant across both treatment arms was Delta (99%), mostly clade 21J.

The baseline demographic and disease characteristics were balanced between the Paxlovid and placebo groups.

The determination of primary efficacy was based on a planned interim analysis of 754 participants in mITT population. The estimated risk reduction was -6.5% with unadjusted 95% CI of (‑9.3%, ‑3.7%) and a 95% CI of (-10.92%, -2.09%) when adjusting for multiplicity. The 2-sided p-value was < 0.0001 with 2-sided significance level of 0.002.

Table 1 provides results of the primary endpoint in the mITT1 analysis population for the full data set at final study completion.

Table 1: Efficacy results in nonhospitalised adults with COVID-19 dosed within 5 days of symptom onset who did not receive COVID-19 mAb treatment at baseline (mITT1 analysis setb)1
COVID-19–related hospitalisation or death from any cause through Day 281
  PAXLOVID
N=977
Placebo
N=989
n=patients with events (%)  9 (0.9%) 64 (6.5%)
Absolute reduction relative to placeboa [95% CI], %  -5.64 (-7.31, -3.97) N/A
p-value  < 0.0001  
All-cause mortality through Day 28, % 0 12 (1.2%)
CI=confidence interval; COVID-19=Coronavirus Disease 2019; mAb=monoclonal antibody; mITT1=modified intent-to-treat 1 (all participants randomly assigned to study intervention, who took at least 1 dose of study intervention, with at least 1 post-baseline visit through Day 28, who at baseline did not receive nor were expected to receive COVID-19 therapeutic mAb treatment and were treated ≤ 5 days after COVID-19 symptom onset).

a. The estimated cumulative proportion of participants hospitalised or death by Day 28 was calculated for each treatment group using the Kaplan-Meier method, where participants without hospitalisation and death status through Day 28 were censored at the time of study discontinuation.
b. Data analysis set was updated after post-hoc removal of data for 133 participants due to GCP quality issues

The estimated risk reduction was -6.1% with 95% CI of (‑8.2%, ‑4.1%) in participants dosed within 3 days of symptom onset, and –4.6% with 95% CI of (-7.4%, -1.8%) in the mITT1 subset of participants dosed > 3 days from symptom onset.

Consistent results were observed in the final mITT and mITT2 analysis populations. A total of 1318 participants were included in the mITT analysis population. The event rates were 5/671 (0.75%) in the Paxlovid group, and 44/647 (6.80%) in the placebo group.

Table 2: Progression of COVID-19 (hospitalisation or death) through Day 28 in symptomatic adults at increased risk of progression to severe illness; mITT1 analysis set1
 
  PAXLOVID
300 mg/100 mg
Placebo
Number of patients N=977 N=989
Serology Negative n=475 n=497
Patients with hospitalisation or deatha (%)
Estimated proportion over 28 days [95% CI], %
Estimated reduction relative to placebo
[95% CI]  
 
8 (1.7%)

1.72 (0.86, 3.40)

-9.79(-12.86, -6.72 )
 
56 (11.3%)

11.50 (8.97, 14.68)


 
Serology Positive n=490 n=479
Patients with hospitalisation or deatha (%)

Estimated proportion over 28 days [95% CI], %

Estimated reduction relative to placebo [95% CI] 
 
1 (0.2%)

0.20 (0.03, 1.44)

-1.5 (-2.70, -0.25)
 
8 (1.7%)

1.68 (0.84, 3.33)


 
CI=confidence interval; COVID-19=Coronavirus Disease 2019; mITT1=modified intent-to-treat 1 (all participants randomly assigned to study intervention, who took at least 1 dose of study intervention, who at baseline did not receive nor were expected to receive COVID 19 therapeutic monoclonal antibody treatment and were treated ≤ 5 days after COVID-19 symptom onset).

Seropositivity was defined if results were positive in a serological immunoassay specific for host antibodies to either S or N viral proteins. The difference between the proportions in the 2 treatment groups and its 95% confidence interval based on normal approximation of the data are presented.

a. COVID-19 related hospitalisation or death from any cause.


Efficacy results for mITT1 were consistent across subgroups of participants including age (≥ 65 years) and BMI (BMI > 25 and BMI > 30) and diabetes.

You can also view information about the EPIC-HR clinical study on clinicaltrials.gov.

What were the most frequently reported adverse reactions?
The most common adverse reactions reported during treatment with PAXLOVID (nirmatrelvir/ritonavir 300 mg/100 mg) in the EPIC-HR trial were dysgeusia (4.6%), diarrhoea (3.0%), headache (1.2%), and vomiting (1.2%)1*.

*Not serious adverse events and were resolved.1

Adverse reactions reported in clinical trials and spontaneous reporting [here]

 
For more information about adverse reactions, see Section 4.8: Undesirable effects of the SmPC [here].
How do I report a suspected adverse reaction? 

Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via HPRA Pharmacovigilance. Website www.hpra.ie.

For more information about adverse reactions, see Section 4.8: Undesirable effects of the SmPC [here]

If you wish to report an adverse event please email Pfizer at [email protected] or contact Pfizer at 1800 633 363. If you have a medical information enquiry or product quality complaint please email [email protected] or contact Pfizer at 1800 633 363. If you have a general enquiry please contact Pfizer Healthcare Ireland, 9 Riverwalk, National Digital Park, Citywest Business Campus, Dublin 24.

Prescribing PAXLOVIDWhat is the dosage of PAXLOVID? 

The recommended dosage in adult patients is 300 mg nirmatrelvir (two 150-mg tablets) with 100 mg ritonavir (one 100-mg tablet), all taken together orally every 12 hours for 5 days. PAXLOVID should be administered as soon as possible after a diagnosis of COVID-19 has been made and within 5 days of symptom onset.1 Patients take the PAXLOVID treatment course orally, every 12 hours, for 5 days.1 Completion of the full 5-day treatment course is recommended even if the patient requires hospitalisation due to severe or critical COVID-19 after starting treatment with PAXLOVID.1

Morning Dose

  • Two pink 150-mg tablets of nirmatrelvir
  • One white 100-mg tablet or ritonavir

Patients should take all 3 tablets together.

Evening Dose

  • Two pink 150-mg tablets of nirmatrelvir
  • One white 100-mg tablet or ritonavir

Patients should take all 3 tablets together.

Dosing for Patients with Renal Impairment
No dose adjustment is needed in patients with mild renal impairment (eGFR ≥60 to <90 mL/min). 

In patients with moderate renal impairment (eGFR ≥30 to <60 mL/min), the dose of PAXLOVID should be reduced to nirmatrelvir/ritonavir 150 mg/100 mg every 12 hours for 5 days to avoid overexposure (this dose adjustment has not been clinically tested). 

PAXLOVID should not be used in patients with severe renal impairment [eGFR <30 mL/min, including patients with End Stage Renal Disease (ESRD) under haemodialysis]. 

Dosing in Patients with Hepatic Impairment
No dose adjustment of PAXLOVID is needed for patients with either mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment. PAXLOVID should not be used in patients with severe (Child-Pugh Class C) hepatic impairment.

How do patients take PAXLOVID?

Nirmatrelvir must be coadministered with ritonavir. Failure to correctly coadminister nirmatrelvir with ritonavir will result in plasma levels of this active substance that will be insufficient to achieve the desired therapeutic effect. PAXLOVID can be taken with or without food. The tablets should be swallowed whole and not chewed, broken, or crushed.1

How soon after my patient tests positive for SARS-CoV-2 should they initiate treatment with PAXLOVID? 

PAXLOVID should be administered as soon as possible after a diagnosis of COVID-19 has been made and within 5 days of symptom onset.1
For more information about dosage, see Section 4.2: Posology and method of administration of the SmPC [here]

Can I prescribe PAXLOVID to pregnant patients or women of childbearing years? 

There are no data on the use of PAXLOVID in pregnant women to inform the drug-associated risk of adverse developmental outcomes; as a precautionary measure, women of childbearing potential should avoid becoming pregnant during treatment with PAXLOVID and for 7 days after completing PAXLOVID.

Use of ritonavir may reduce the efficacy of combined hormonal contraceptives. Patients using combined hormonal contraceptives should be advised to use an effective alternative contraceptive method or an additional barrier method of contraception during treatment with PAXLOVID and until 1 menstrual cycle after stopping PAXLOVID.

PAXLOVID is not recommended during pregnancy and in women of childbearing potential not using contraception unless the clinical condition requires treatment with PAXLOVID.1

For more information and data from embryo-fetal developmental toxicity studies with nirmatrelvir and ritonavir, see Section 4.6: Fertility, pregnancy, and lactation and Section 5.3: Preclinical safety data of the SmPC [here].

What does a blister card of PAXLOVID look like? 

PAXLOVID film-coated tablets are available in 5 daily-dose blister cards, with a total of 30 tablets packaged in a carton. Each daily blister card contains 4 nirmatrelvir tablets (150 mg each) and 2 ritonavir tablets (100 mg each) and indicates which tablets need to be taken in the morning and evening (sun and moon symbols).

  • Nirmatrelvir 150-mg, film-coated tablets are pink, oval shaped, and debossed with ‘PFE’ on one side and ‘3CL’ on the other side
  • Ritonavir 100-mg, film-coated tablets are white to off-white, capsule shaped, and debossed with ‘H’ on one side and ‘R9’ on the other side                                                                                                                                      

For more information, see Section 3: Pharmaceutical form of the SmPC [here]. 

What if patients take PAXLOVID incorrectly? 

Instructions for a missed dose1:

  • If the patient misses a dose of PAXLOVID within 8 hours of the time it is usually taken, advise the patient to take it as soon as possible and resume the normal dosing schedule
  • If the patient misses a dose by more than 8 hours, tell them to not take the missed dose and to instead take the next dose at the regularly scheduled time
  • The patient should not double the dose to make up for a missed dose  

Instructions for an overdose1:

  • Treatment of overdose with PAXLOVID should consist of general supportive measures, including monitoring of vital signs and observation of the clinical status of the patient
  • There is no specific antidote for overdose with PAXLOVID
Product SafetyWho can I call with medical questions? 

For medical questions related to PAXLOVID, you can visit www.pfizermedicalinformation.ie or call Medical Information at 1800 633 363.

What are the contraindications for PAXLOVID? 

PAXLOVID is contraindicated in/with:                                                                                                                              

  • Hypersensitivity to the active substances or to any of the excipients in Section 6.1: List of excipients [here]
  • Medicinal products that are highly dependent on CYP3A for clearance and for which elevated concentrations are associated with serious and/or life-threatening reactions 
  • Medicinal products that are potent CYP3A inducers where significantly reduced nirmatrelvir/ritonavir plasma concentrations may be associated with the potential for loss of virologic response and possible resistance                                                                    
Paxlovid cannot be started immediately after discontinuation of CYP3A4 inducers due to the delayed offset of the recently discontinued CYP3A4 inducer (see section 4.5).

A multi-disciplinary approach (e.g., involving physicians and specialists in clinical pharmacology) should be considered to determine the adequate timing for Paxlovid initiation taking into account the delayed offset of the recently discontinued CYP3A inducer and the need to initiate Paxlovid within 5 days of symptom onset.

For a list of potential clinically significant drug interactions, including contraindicated drugs, refer to Section 4.3: Contraindications, Section 4.5: Interaction with other medicinal products and other forms of interaction and Table 1: Interaction with other medicinal products and other forms of interaction of the SmPC [here].
What are the potential drug interactions with PAXLOVID? 

Paxlovid (nirmatrelvir/ritonavir) is a strong inhibitor of CYP3A and increases plasma concentrations of medicinal products that are primarily metabolised by CYP3A. Thus, coadministration of nirmatrelvir/ritonavir with medicinal products highly dependent on CYP3A for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events is contraindicated (see Table 1 of SmPC). Coadministration of other CYP3A4 substrates that may lead to potentially significant interaction (see Table 1 of SmPC) should be considered only if the benefits outweigh the risks.

Management of drug-drug interactions (DDIs) in high-risk COVID-19 patients receiving multiple concomitant medications can be complex and require a thorough understanding of the nature and magnitude of interaction with all concomitant medications. In certain patients, a multi-disciplinary approach (e.g., involving physicians and specialists in clinical pharmacology) should be considered for management of DDIs especially if concomitant medications are withheld, their dosage is reduced, or if monitoring of side effects is necessary.

Initiation of PAXLOVID, a CYP3A inhibitor, in patients receiving medicinal products metabolised by CYP3A or initiation of medicinal products metabolised by CYP3A in patients already receiving PAXLOVID, may increase plasma concentrations of medicinal products metabolised by CYP3A.
                                                                     
Coadministration of Paxlovid with calcineurin inhibitors and mTOR inhibitors
Consultation of a multidisciplinary group (e.g., involving physicians, specialists in immunosuppressive therapy, and/or specialists in clinical pharmacology) is required to handle the complexity of this coadministration by closely and regularly monitoring immunosuppressant serum concentrations and adjusting the dose of the immunosuppressant in accordance with the latest guidelines. See section 4.5 of the SmPC [here].

 Initiation of medicinal products that inhibit or induce CYP3A may increase or decrease concentrations of PAXLOVID, respectively. These interactions may lead to:

  • Clinically significant adverse reactions, potentially leading to severe, life-threatening, or fatal events from greater exposures of concomitant medicinal products 
  • Clinically significant adverse reactions from greater exposures of PAXLOVID       
  • Loss of therapeutic effect of PAXLOVID and possible development of viral resistance                                                                                  

See Table 1 of SmPC for medicinal products that are contraindicated for concomitant use with nirmatrelvir/ritonavir and for potentially significant interactions with other medicinal products. See section 4.5 [here]. Potential for interactions should be considered with other medicinal products prior to and during Paxlovid therapy; concomitant medicinal products should be reviewed during Paxlovid therapy and the patient should be monitored for the adverse reactions associated with the concomitant medicinal products.

How can I determine if the product is authentic? 

Authentic PAXLOVID from Pfizer Inc. will include the Pfizer name on the label and will be packaged in 5 foil push-through blister cards. Individual doses are not for sale. PAXLOVID™ will be packaged in a rectangular carton. The carton has a colorless, glossy coating that contains a repeated pattern of the Pfizer name and logo all over, and these repeating features are seen in a contrasting matte finish. PAXLOVID film-coated tablets are available in 5 daily-dose blister cards with a total of 30 tablets. Each daily blister card contains 4 nirmatrelvir tablets (150 mg each) and 2 ritonavir tablets (100 mg each) and indicates which tablets need to be taken in the morning and evening (sun and moon symbols). Nirmatrelvir 150 mg film coated tablets are pink, oval-shaped, and debossed with 'PFE' on one side and '3CL' on the other side. Ritonavir 100 mg film-coated tablets are white to off-white, capsule-shaped, and debossed with 'H' on one side and 'R9' on the other side.1

See more information about product authenticity [here].

References:
  1. PAXLOVID Summary of Product Characteristics. https://www.medicines.ie/medicines/paxlovid-150-mg-100-mg-film-coated-tablets-35210/spc#tabs (Accessed October 2023).
  2. Oral COVID-19 antiviral, Paxlovid, approved by UK regulator - GOV.UK https://www.gov.uk/government/news/oral-covid-19-antiviral-paxlovid-approved-by-uk-regulator  (Accessed October 2023).
 
This medicinal product is subject to additional monitoring. This will allow quick identification of new safety information. Healthcare professionals are asked to report any suspected adverse reactions. See section 4.8 of the SmPC for how to report adverse reactions.
 

Legal Category: S1A
Further information is available upon request

PP-PAX-IRL-0178. October 2023

Adverse events should be reported. Report an adverse event to your national reporting system (HPRA Pharmacovigilance)
 

Adverse events should also be reported to Pfizer Medical Information on 1800 633 363

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