Nirmatrelvir / Ritonavir

UK SPC (Paxlovid 150 mg/100 mg film-coated tablets) section 4.2, verbatim: 'The recommended dosage is 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) all taken together orally twice daily every 12 hours for 5 days.' || MISSED DOSE: 'A missed dose should be taken as soon as possible and within 8 hours of the scheduled time, and the normal dosing schedule should be resumed. If more than 8 hours has elapsed, the missed dose should not be taken and the treatment should resume according to the normal dosing schedule.' || HOSPITALISATION: 'If a patient requires hospitalisation due to severe or critical COVID-19 after starting treatment with Paxlovid, the patient should complete the full 5-day treatment course at the discretion of his/her healthcare provider.' || RENAL IMPAIRMENT (Table 1) - MILD (eGFR 60 to under 90 mL/min): no dosage adjustment needed. MODERATE (eGFR 30 to under 60 mL/min), days 1 to 5: 150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) twice daily. SEVERE (eGFR under 30 mL/min) including those requiring haemodialysis - day 1: 300 mg nirmatrelvir (two 150 mg tablets) with 100 mg ritonavir (one 100 mg tablet) once; days 2 to 5: 150 mg nirmatrelvir (one 150 mg tablet) with 100 mg ritonavir (one 100 mg tablet) once daily. Administer at approximately the same time each day for 5 days; on haemodialysis days give the dose after haemodialysis. The SPC warns that the daily dose pack provided may contain MORE tablets than needed for accurate dosing in moderate and severe renal impairment, and that patients must be alerted to this; remaining tablets should be disposed of in accordance with local requirements. || HEPATIC IMPAIRMENT: no dosage adjustment for mild (Child-Pugh Class A) or moderate (Child-Pugh Class B); contraindicated in severe (Child-Pugh Class C) hepatic impairment. || ELDERLY: 'No dosage adjustment is currently recommended for elderly patients.' || CONCOMITANT RITONAVIR- OR COBICISTAT-CONTAINING REGIMEN: 'No dosage adjustment is needed; the dose of Paxlovid is 300 mg/100 mg twice daily for 5 days. Patients diagnosed with human immunodeficiency virus (HIV) or hepatitis C virus (HCV) infection who are receiving ritonavir- or cobicistat-containing regimen should continue their treatment as indicated.' || DRUG INTERACTIONS ARE THE MAIN HAZARD: section 4.4 records that 'Severe, life-threatening, and fatal adverse reactions due to drug interactions have been reported in patients treated with Paxlovid.' Review every concomitant medicine before and during therapy. Coadministration with calcineurin inhibitors and mTOR inhibitors requires consultation of a multidisciplinary group with close, regular monitoring of immunosuppressant blood concentrations and dose adjustment per the latest guidelines. || Section 4.3's contraindicated-medicines table (Table 2) was cut at the source-fetch limit part-way through 'Cardiovascular agents', and sections 4.4 and 4.6 were also cut, so the contraindication and warning lists below are NOT complete - consult the full SPC and the interaction tables before prescribing.

NO PAEDIATRIC DOSE EXISTS IN THIS SOURCE, so dosePerKg is null and the weight calculator is deliberately unset. Section 4.2 verbatim: 'Paediatric population The safety and efficacy of Paxlovid in paediatric patients younger than 18 years of age have not yet been established.' Section 4.8 repeats: 'The safety and efficacy of Paxlovid in paediatric patients have not been established.' The adult dose is a fixed tablet regimen and is not weight-based; do not scale it or split tablets for children (the tablets must be swallowed whole and not chewed, broken or crushed). Verify against a children's formulary.