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Pharmacokinetics of rectal paracetamol after major surgery in children
B J Anderson1, G A Woolard, N H Holford
1Department of Anaesthesia, Auckland Hospital, New Zealand.
Insights
Paracetamol suppositories administered rectally to children after orthopedic surgery achieved therapeutic antipyretic plasma concentrations within 1-2 hours. However, some individuals may not reach optimal paracetamol levels for pain relief.
Area of Science:
- Pharmacology
- Pediatric Medicine
- Anesthesiology
Background:
- Postoperative pain and fever management in children is critical.
- Paracetamol (acetaminophen) is a common analgesic and antipyretic agent.
- Rectal administration offers an alternative route for pediatric medication delivery.
Purpose of the Study:
- To evaluate the plasma concentrations of paracetamol following rectal administration in pediatric patients.
- To determine the pharmacokinetic profile of paracetamol suppositories in children undergoing orthopedic surgery.
- To assess the achievement of therapeutic paracetamol levels for antipyretic effects.
Main Methods:
- 20 pediatric patients (12 months-17 years) received 40 mg/kg paracetamol suppositories post-orthopedic surgery.
- Plasma paracetamol concentrations were measured for up to 18 hours.
- Key pharmacokinetic parameters including Cmax, Tmax, and clearance were analyzed.
Main Results:
- Mean maximum paracetamol concentration (Cmax) was 0.115 mmol/L, with peak concentration (Tmax) at 2.3 hours.
- Therapeutic antipyretic concentrations (0.066-0.130 mmol/L) were achieved within 1-2 hours post-administration.
- A high coefficient of variance (43%) for Cmax suggests variability in individual patient responses.
Conclusions:
- Rectal paracetamol at 40 mg/kg provides effective perioperative antipyretic plasma concentrations in children.
- The rapid achievement of therapeutic levels aligns with the recovery phase of pediatric surgery.
- Individual variability in Cmax indicates a potential for sub-therapeutic levels in some patients, warranting further investigation.
Abstract:
Glycogelatin capsular suppositories containing a paracetamol slurry 40 mg.kg-1 were given PR to 20 children (12 months-17 yrs) after major orthopaedic surgery and plasma concentrations of paracetamol measured for up to 18 h. The mean maximum concentration (Cmax) was 0.115 (SD 0.049) mmol.l-1. Peak concentration occurred (Tmax) at 2.3 (SD 1.2) h. Mean concentration was 0.07 (SD 0.03) mmol.l-1 at six h. Apparent paracetamol clearance was 5.8 ml.min-1.kg-1. The plasma concentration of paracetamol associated with analgesic effectiveness in children is unknown, but antipyretic effects are seen in the range 0.066-0.130 mmol.l-1. Paracetamol suppositories 40 mg.kg-1 given perioperatively achieve effective therapeutic antipyretic plasma concentrations within 1-2 h. The timing is coincident with the recovery phase of short duration paediatric surgery. The coefficient of variance of Cmax was 43%. Some individual patients may not achieve a Cmax which is therapeutic.