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Nirmatrelvir

Antiviralprescriptionoral · inferred

SARS-CoV-2 main protease (Mpro / 3CLpro) inhibitor. Almost always co-administered with low-dose ritonavir (as Paxlovid) for CYP3A4 inhibition, which raises nirmatrelvir exposure several-fold. Standalone entry exists for completeness; most users should log Paxlovid.

Projected serum levels — 300 mg, twice daily

Nirmatrelvir
Nirmatrelvir modeled serum levels, 300 mg twice daily over 15 days Population-based pharmacokinetic estimate. Steady state reached after approximately 1 days. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule ≈ steady state · day 1
Nirmatrelvir modeled serum levels with a loading dose of 434 mg, then 300 mg twice daily The first dose is larger so levels approach steady state faster. 0 50 100 150 200 Day 0 Day 4 Day 7 Day 11 Day 15 Time on a regular schedule

Maintenance schedule: 300 mg twice daily (oral).

Loading schedule: 434 mg on day 1, then 300 mg twice daily — reaching therapeutic levels sooner.

Modeled steady state after ~1 days: peak ≈ 163 mg, trough ≈ 65.3 mg body load. Population-based estimate over 15 days for a 300 mg dose at a 70 kg reference body mass — the interactive app scales curves to your doses, timing, and body mass.

Key facts

Category
Antiviral
Route modeled
Oral
Model confidence
inferred
Half-life
7 h
Common dose
300 mg
Suggested maximum
300 mg/day
Reference dose range
150–300 mg (single dose)
Suggested cadence
twice daily
Validated against
300 mg oral — Cmax 2.2 mg/L at 3 h

Documented interactions

  • contraindicated
    Carbamazepine (Tegretol) + Nirmatrelvir CYP induction

    Carbamazepine (Tegretol) inducer of CYP3A4 predicted to change Nirmatrelvir AUC by ~0.20x

  • contraindicated
    Clarithromycin (Biaxin) + Nirmatrelvir CYP inhibition

    Clarithromycin (Biaxin) mechanism_based of CYP3A4 predicted to change Nirmatrelvir AUC by ~10.00x

  • contraindicated
    Dasatinib (Sprycel) + Nirmatrelvir CYP inhibition

    Dasatinib (Sprycel) time_dependent_inhibitor of CYP3A4 predicted to change Nirmatrelvir AUC by ~5.00x

  • contraindicated
    Diltiazem + Nirmatrelvir CYP inhibition

    Diltiazem mechanism_based of CYP3A4 predicted to change Nirmatrelvir AUC by ~10.00x

  • contraindicated
    Efavirenz (Sustiva) + Nirmatrelvir CYP induction

    Efavirenz (Sustiva) inducer of CYP3A4 predicted to change Nirmatrelvir AUC by ~0.12x

  • contraindicated
    Grapefruit (whole fruit) + Nirmatrelvir CYP inhibition

    Grapefruit (whole fruit) mechanism_based of CYP3A4 predicted to change Nirmatrelvir AUC by ~10.00x

Serum checks 274 modeled interaction pairings for nirmatrelvir across your whole stack — absorption conflicts, enzyme inhibition, and nutrient depletion included.

Research behind this entry

  1. An oral SARS-CoV-2 M(pro) inhibitor clinical candidate for the treatment of COVID-19 Owen DR et al. · Science, 2021 DOI

    Discovery and preclinical characterization of nirmatrelvir (PF-07321332), a covalent Mpro inhibitor with oral bioavailability.

  2. Oral Nirmatrelvir for High-Risk, Nonhospitalized Adults with Covid-19 Hammond J et al. · New England Journal of Medicine, 2022 DOI

    EPIC-HR Phase 2/3 RCT showing 89% reduction in hospitalization/death with nirmatrelvir-ritonavir started within 3 days of symptom onset.

  3. Pharmacokinetics, Pharmacodynamics, and Drug-Drug Interactions of Nirmatrelvir/Ritonavir Singh RSP et al. · Clinical and Translational Science, 2022 DOI

    Characterizes nirmatrelvir clearance, ritonavir boost effect, and major CYP3A4 interactions with concomitant medications.

3 published studies referenced in the app, each with a plain-language summary.