Paracetamol

Paracetamol

There is very little downside to prescribing oral paracetamol preoperatively. It is a cheap and effective opioid-sparing agent which is well tolerated.

Uses:

Analgesic and antipyretic.

Preparations:

• PO tablet or liquid formulations of varying strengths
• IV Clear colourless 10mg/ml solution
• PR suppository

Actions:

• Analgesia
• Anit-pyretic
• Anti-inflammatory

The exact mechanism of action is unclear but it acts on multiple receptors including COX1/2 (cyclooxygenase), 5HT₃ (serotonin) and CB1 (cannabinoid) receptors.

Benefits:

• Analgesic and anaesthetic sparing effect
• Decreased postoperative nausea and vomiting
• Improved intestinal motility
• Enhanced recovery

Proven benefit in bowel surgery in terms of return of normal function and lower postoperative pain scores.

Dose:

15 mg/kg every 6 hours.

The plasma level achieved at recommended levels is relatively low. Although, toxicity is rare patients should be monitored for clinical signs and symptoms.

Onset:

• PO: 45 minutes to peak plasma level with peak analgesic time 1-2 hours after.
• IV: 20 minutes to peak plasma level with peak analgesic time 1-2 hours after.

Kinetics:

• Bioavailablity 63-89% (Oral), 100% (Intravenous)
• Elimination half-life ~ 2hours
• Plasma protein binding ~ 70-80%
• Metabolized by the liver
• Excreted in the urine

Rectal administration has unpredictable bioavailability and low patient acceptability. This route can be considered if alternatives are not feasible.

Caution:

• Liver Failure