Effect of 3 g of intravenous paracetamol on post-operative analgesia, platelet function and liver enzymes in patients undergoing tonsillectomy under local anaesthesia.

BACKGROUND: Paracetamol is often given as an adjunctive analgesic to reduce opioid-related adverse effects but its optimal dose is unknown. We studied the analgesic effect and safety of a single 3-g intravenous (i.v.) dose of paracetamol in adults. METHODS: One hundred and seven patients undergoing tonsillectomy under local anaesthesia were randomly allocated to receive i.v. 3 g of paracetamol, 75 mg of diclofenac or placebo prior to surgery. The consumption of post-operative morphine using a patient-controlled analgesia-device was quantified for 6 h. Platelet aggregation and the concentrations of paracetamol, liver aminotransferases, glutathione transferase alpha 1-1 (GSTA1-1) and thromboxane B(2) were measured. RESULTS: During the first hours after surgery, both paracetamol and diclofenac reduced (P < 0.05) the consumption of morphine but had no effect thereafter. The values for the 6-h cumulative consumption of morphine in patients given paracetamol (18.7 +/- 13.8 mg), diclofenac (16.1 +/- 9.9 mg) and placebo (22.0 +/- 12.1 mg) did not differ. Paracetamol had no effect on platelet aggregation, which was impaired only by diclofenac in response to arachidonic acid (P < 0.005). Both paracetamol (P < 0.01) and diclofenac (P < 0.005) inhibited the release of thromboxane B(2) at 1 h but they did not affect serum aminotransferase and GSTA1-1 levels. One patient given paracetamol displayed a transient increase in GSTA1-1 and liver aminotransferases. CONCLUSION: During the initial hours after tonsillectomy, the administration of 3 g of i.v. paracetamol and 75 mg of diclofenac reduced the consumption of morphine. Both drugs also reduced the release of thromboxane B(2) from activated platelets but only diclofenac had a negative effect on platelet aggregation. In sensitive individuals, large doses of paracetamol may disturb the hepatocellular integrity. We do not recommend the use of i.v. doses of paracetamol higher than 1 g.

Comparison of the opioid-sparing efficacy of diclofenac and ketoprofen for 3 days after knee arthroplasty.

BACKGROUND: Comparative postoperative non-steroidal anti-inflammatory drug (NSAID) studies in orthopedic patients have usually been restricted in time to the first postoperative day. The opioid-sparing effect of NSAIDs may be beneficial postoperatively as long as pain otherwise restricts ambulation and rehabilitation. We therefore compared the analgesic efficacy of the maximum recommended doses of diclofenac and ketoprofen for 3 days after knee arthroplasty. METHODS: We studied 64 knee arthroplasty patients, operated on under spinal anesthesia. In a randomized, double-blind and placebo-controlled fashion, the patients received either i.v. diclofenac 75 mg (n = 24), ketoprofen 100 mg (n = 24) or saline (n = 16) in the recovery room, followed by oral diclofenac 150 mg/day, ketoprofen 300 mg/day or placebo, respectively, for 3 days, supplemented by patient-controlled analgesia (PCA) with i.v. oxycodone. RESULTS: The mean consumption of oxycodone during the first, second and third study days was 45.3, 22.3 and 15.2 mg in the diclofenac group, 43.5, 37.5 and 21.8 mg in the ketoprofen group, and 61.2, 45.9 and 36.1 mg, respectively, in the placebo group. Oxycodone consumption was significantly lower (P < 0.05) in the ketoprofen group than in the placebo group in the postoperative period 13-24 h and 61-72 h. Diclofenac was superior to placebo in the postoperative period 25-48 h (P < 0.01), 49-60 h (P < 0.05) and to ketoprofen at 49-60 h (P < 0.05). During administration of diclofenac on days 1-3 and ketoprofen on day 2, the mean pain scores (VAS) were lower than in the placebo group (P < 0.05). Six patients had difficulties in operating the PCA device. There were no differences in blood loss. CONCLUSION: We conclude that in the first day after knee arthroplasty (13-24 h), ketoprofen exerted an opioid-sparing effect. After day 1 (25-60 h), with the doses used, diclofenac proved to be better than placebo, whereas ketoprofen was not.