Paracetamol is available both as an intravenous preparation and as a suppository. It can be given intraoperatively in the same dose as is given orally: usually 1 g for an adult patient.

The vial contains 1 g of paracetamol as a solution in 100 ml; this should be given intravenously over about 20 min.

If the suppository formulation is to be used, it should be placed per rectum after induction of anaesthesia and before surgery starts to allow time for absorption.

The rectal route is less reliable than the intravenous route for drug administration, but is sometimes preferred for very short duration surgery.

The duration of action of paracetamol is much longer than for the intravenous opioids; a repeat dose is rarely used unless surgery takes more than 6 h.

It is useful to combine paracetamol and fentanyl in theatre, since paracetamol has a small opioid-sparing effect that not only allows less fentanyl to be used, but can reduce the postoperative opioid requirements by a small amount (10-20%).