Route selection (PO first-line when tolerated · IV when NPO or vomiting/unable to take oral · rectal when PO/IV unavailable — **do not combine routes** without accounting for total 24 h dose (NHS SPS, BNFC))
First-line therapy
Paracetamol • p.o. • 10–15 mg/kg/dose • 4×/day
Max 1000 mg/dose · Max 4000 mg/day · Duration: PRN · 10–15 mg/kg/dose q4–6 h PRN — max 4 doses/24 h; neonates use with caution and specialist advice
• Maximum daily dose: **60 mg/kg/day OR 4000 mg/day (4 g/day) whichever is lower** — applies to all routes; include loading doses in 24 h total; calculator caps at 4 g/day — verify weight-based limit for children <67 kg (BNFC, AAP, NICE CKS).
• Maximum single dose: **1000 mg (1 g)** per administration for all routes in standard paediatric use (BNFC, AAP, WHO).
• IV age/weight restrictions (Perfalgan SmPC, BNFC): typically **≥33 weeks gestational age** with weight appropriate to product labelling; preterm neonates require specialist neonatal dosing (e.g. 7.5–10 mg/kg q8–12 h, max 30 mg/kg/day) — do not use standard 15 mg/kg q4h calculator values without NICU protocol.
• Rectal loading dose (BNFC): if no paracetamol in preceding 24 h, **20 mg/kg** (max 1 g) once, then maintenance 15 mg/kg q4–6 h — some protocols use 30–40 mg/kg loading when oral/IV unavailable; counts toward daily maximum (BNFC, NHS Highland analgesia guideline).
• Postoperative short-term higher daily limits (e.g. 90 mg/kg/day for ≤48 h) exist in some surgical protocols — use only per local postoperative pain guideline, not routine outpatient dosing (AAP, institutional APRS protocols).
Enter weight on Kids to calculate doses
Paracetamol • rectal • 20–20 mg/kg/dose • 1×/day
Max 1000 mg/dose · Max 4000 mg/day · Duration: Once · 20 mg/kg single loading dose (max 1 g) if no paracetamol in prior 24 h — then maintenance 15 mg/kg q4–6 h
• Rectal loading 20 mg/kg: BNFC recommended initial dose when no paracetamol given in preceding 24 h — then 15 mg/kg q4–6 h maintenance; counts toward 60 mg/kg/day maximum (BNFC, NICE CKS).
• Rectal loading 30–40 mg/kg: some institutional protocols when PO/IV unavailable and higher loading needed — max 1 g single dose; specialist/regional guidance only; higher hepatotoxicity risk if repeated (NHS Highland, SESLHD).
• Neonatal IV 7.5–10 mg/kg: preterm and term neonates per BNFC/NICU nomogram — extended intervals (q8–12 h), lower daily max (30 mg/kg/day) — **do not use standard child IV tier** without pharmacy/neonatology sign-off (BNFC, NHS SPS, Perfalgan SmPC).
• Hepatic impairment / malnutrition / chronic illness: reduce dose (e.g. 10 mg/kg) and extend interval to q8 h; max 30 mg/kg/day — avoid repeated supratherapeutic dosing (BNFC, APRS Scotland).
• Switch IV → PO at earliest opportunity; review IV courses >48 h — consider LFTs/INR per local protocol (BNFC, NHS SPS, institutional guidelines).
Enter weight on Kids to calculate doses
Clinical notes
• Avoid duplicate paracetamol: check all combination cold/flu/cough products, co-prescribed analgesics, and parental OTC dosing — cumulative 24 h dose must include every source; educate caregivers to use single-ingredient paracetamol only (BNFC, MHRA, NHS SPS).
• Liver disease, malnutrition, cystic fibrosis, chronic illness, and fasting: reduce dose and/or extend interval (e.g. 10 mg/kg q8 h, max 30 mg/kg/day); avoid repeated doses near daily maximum; consult hepatology in chronic liver disease (BNFC, APRS Scotland).
• Overdose and NAC: single ingestion **≥150 mg/kg** (lower threshold in at-risk children) risks severe hepatotoxicity — urgent paediatric toxicology, serum paracetamol level at ≥4 h post-ingestion, start N-acetylcysteine per local/Toxbase nomogram without waiting for level if high-risk presentation (BNFC, Toxbase, AAP).
• IV safety: 10 mg/mL concentration — **never confuse mg with mL** (ten-fold overdose risk); infuse over ≥15 min; use partial vial protocols for neonates/infants; two-person check for prescriptions and administration especially <10 kg (NHS SPS, MHRA, institutional policy).
• Route discipline: specify **one route** on prescription; do not give IV and PO concurrently without explicit 24 h dose accounting; switch IV → enteral at earliest opportunity; rectal absorption is variable — reassess clinical response (BNFC, NHS SPS, NICE CKS).
• BNF for Children (BNFC) — Paracetamol oral, IV, and rectal dosing (2025)
