Paxlovid Prescribing Reference

Nirmatrelvir 150 mg + ritonavir 100 mg co-packaged. Clinician quick reference for dosing by renal function, missed-dose rules, critical drug interactions, monitoring. Australian PBS-listed for eligible patients within 5 days of symptom onset.

📋 Sources: TGA Product Information (Paxlovid, finalised 5 November 2024); RACGP — Advice to prescribers and dispensers of Paxlovid; PBS Schedule; Australian Commission on Safety and Quality in Health Care. Verified June 2026.
Clinician reference, not a substitute for the full Product Information. Use clinical judgement; verify current PBS authority criteria for each patient; check for drug interactions every time.

⚠ Use clinical judgement. Paxlovid has many clinically significant drug interactions, some absolute contraindications. Always check the patient's full medication list (including OTC, herbal, recent ceased) against an authoritative interactions resource before prescribing. This page is a reference, not a checker — it does not replace per-patient verification.

PBS authority Authority Required (STREAMLINED) — Category GE (General Schedule). For verified SARS-CoV-2 infection. Treatment must be initiated within 5 days of symptom onset. PBS Schedule for full criteria.

Take BOTH tablets together — always Nirmatrelvir must be taken with ritonavir. Skipping the ritonavir produces subtherapeutic nirmatrelvir plasma levels. If the patient cannot tolerate ritonavir, the course is not effective — do not advise taking nirmatrelvir alone.

Dosing tool — by eGFR

Enter the patient's eGFR (mL/min/1.73m²) to get the regimen. Three tiers per the TGA PI (Nov 2024).

eGFR (mL/min/1.73m²) On haemodialysis

All three regimens — reference

Standard dose — eGFR ≥60 mL/min/1.73m² (normal or mild impairment)
Nirmatrelvir 300 mg (2 × 150 mg tablets) + ritonavir 100 mg (1 tablet) taken together BD × 5 days. Approximately 12 hours apart. No dose adjustment for mild impairment.

Reduced dose — eGFR ≥30 to <60 mL/min/1.73m² (moderate impairment)
Nirmatrelvir 150 mg (1 × 150 mg tablet) + ritonavir 100 mg (1 tablet) taken together BD × 5 days. Counsel patient explicitly: only take ONE pink tablet per dose, not two — the carton blister contains the standard dose.

Severe renal impairment dose — eGFR <30 mL/min/1.73m² (incl. haemodialysis)
Day 1: Nirmatrelvir 300 mg (2 × 150 mg) + ritonavir 100 mg, single dose.
Days 2–5: Nirmatrelvir 150 mg (1 × 150 mg) + ritonavir 100 mg, once daily.
On dialysis days: Administer dose after haemodialysis.
⚠ Pack repackaging — counsel the patient. The dispensed pack contains more nirmatrelvir tablets than this regimen requires. The pharmacist should have removed surplus tablets and affixed dosing stickers; check this before the patient leaves the consult. Counsel the patient: take what the sticker says, not what the blister-card layout suggests — or they will overdose.
Dosing added in the TGA PI update finalised Nov 2024; pack-handling guidance confirmed via TGA-mandated prescriber communication, May 2026.

Missed dose

Within 8 hours of the usual time: Take the missed dose as soon as the patient remembers, then resume the normal schedule.
More than 8 hours late: Skip the missed dose. Take the next dose at the regular time.
Never double up. Counsel the patient to complete all 5 days even if they feel better.

Critical drug interactions

Ritonavir is a potent CYP3A4 inhibitor. Many medicines are contraindicated or require dose adjustment / temporary cessation. Always check every patient's full medication list before prescribing.

Authoritative interactions resources to use mid-consult:

University of Liverpool COVID-19 Drug Interactions Checker — the standard reference, regularly updated, free
TGA Product Information — full list of contraindicated and caution medicines in Section 4.5
Australian Medicines Handbook (AMH) Paxlovid monograph for prescribing-context interactions

Categories of concern — contraindicated or requiring action

Absolutely contraindicated (incomplete list — verify):

Alpha-1 adrenoreceptor antagonists: alfuzosin
Antiarrhythmics: amiodarone, dronedarone, flecainide, propafenone, quinidine
Antigout: colchicine (in renal/hepatic impairment)
Antipsychotics: lurasidone, pimozide, clozapine
Cardiovascular: ivabradine, ranolazine, eplerenone
Ergot derivatives
Lipid-lowering: lovastatin, simvastatin (atorvastatin and rosuvastatin require dose adjustment / temporary cessation)
Sedatives/hypnotics: triazolam, oral midazolam
PDE5 inhibitors: sildenafil for pulmonary arterial hypertension
St John's Wort (potent CYP3A4 inducer — reduces nirmatrelvir levels)
Anticonvulsants: carbamazepine, phenobarbital, phenytoin (inducers)
Rifampicin / rifabutin

Common categories requiring adjustment, temporary cessation, or close monitoring:

Statins (most need to be held for the 5 days + a few days after)
Direct oral anticoagulants (apixaban, rivaroxaban — check Liverpool tool for individual recommendations)
Immunosuppressants (tacrolimus, cyclosporin, sirolimus — specialist input usually required)
Inhaled / intranasal / topical corticosteroids (especially fluticasone, budesonide — risk of Cushing's)
SSRIs, SNRIs — usually safe but check individual agents
Many antifungals, antibiotics, antiretrovirals, oncology agents

This list is illustrative. For any specific patient, run the full medication list (including OTC, herbal, recently ceased) through the Liverpool COVID-19 Drug Interactions Checker.

Common adverse effects

From EPIC-HR trial and post-market surveillance. Generally mild and self-limiting.

Dysgeusia (altered or metallic taste) — most common; ~5–6% in trial
Diarrhoea — ~3%
Headache — ~1–2%
Vomiting / nausea / abdominal pain
Hypertension — less common; check BP at follow-up if relevant
Generally feeling unwell / fatigue

Counsel the patient: seek urgent care for signs of allergic reaction (rash, swelling of face/tongue/lips, breathing difficulty) or any unusual effects of concern. Paxlovid is subject to TGA additional monitoring (black triangle ▼) — report adverse events to tga.gov.au/safety/reporting-problems.

When not to use

Severe hepatic impairment (Child-Pugh C) — not recommended (no PK data)
Hypersensitivity to nirmatrelvir, ritonavir, or any excipient
Significant drug interactions that cannot be managed by holding or substituting (see categories above)
More than 5 days from symptom onset — no evidence of benefit; not PBS-eligible
Pregnancy / breastfeeding — not recommended; women of childbearing potential require contraception during and for 7 days after the course
Hospitalised patients with severe/critical COVID — Paxlovid is for community / mild-to-moderate disease, not severe (if patient already hospitalised after starting course, complete at clinician discretion)

Practical prescribing notes

Confirm eligibility (see patient eligibility checker) and current PBS authority criteria before prescribing
Take a thorough medication history including OTC, herbal supplements, and medications recently ceased (residual interaction risk for inducers)
Specify the numeric dose of each active ingredient on the prescription (e.g. "nirmatrelvir 150 mg, ritonavir 100 mg")
Document the patient's eGFR and the regimen chosen in the consultation note
For reduced-dose tier, explicitly counsel: only ONE pink tablet per dose, not two — the blister card is laid out for the standard dose
Consider whether a follow-up at day 3–5 is appropriate (especially elderly, complex med list, or moderate renal impairment)
Counsel patient to seek urgent care if symptoms worsen, breathlessness, or any allergic-type reaction

✅

COVID Antivirals — Eligibility

Patient-facing PBS eligibility checker. Cross-link from consultation when discussing access.

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Long COVID GP Guide

Clinician reference for assessing and managing post-COVID symptoms.

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CKD Stage Calculator

eGFR-based CKD staging — useful for confirming the correct Paxlovid dosing tier.