Single-blind comparative analgesic and safety study of single doses of intramuscularly administered ketorolac tromethamine and pethidine hydrochloride in patients with pain following orthopaedic surgery.

Ketorolac tromethamine, a potent non-narcotic prostaglandin synthetase inhibiting analgesic was compared with pethidine for relief of moderate to severe postoperative pain. Forty-eight patients received Ketorolac 0.5 mg/kg and 52 received pethidine 1.25 mg/kg. The degree of pain prior to the administration of the drug and pain relief that followed were quantified using a vertical visual analogue scale (VAS) and monitored at hourly intervals. The safety profile was also studied by recording all adverse events noted. The mean pain (VAS) score at medication for Ketorolac was 7.04 and for pethidine 7.09. The pain relief obtained in the first four hours following administration of the drugs was similar for pethidine and Ketorolac. Although Ketorolac showed a longer sustained pain relief, time to peak analgesia after administration of this drug was slower than that after pethidine. It took 30 to 50 min for pethidine compared to 75 to 150 min for Ketorolac to achieve peak analgesia. The latter is therefore inappropriate if rapid pain relief is required. The incidence of side effects was significantly greater with pethidine (40.4%) as compared to Ketorolac (10.4%). The similar analgesic efficacy to pethidine makes Ketorolac an appropriate drug for the relief of postoperative pain especially in day surgery settings where observation following administration of the drug as in the case of pethidine can be dispensed with and patients sent home earlier because of the minimal side effects associated with its use. Caution must be exercised with the use of large doses of Ketorolac especially if the drug is used for more than 5 days to avoid serious complications like renal failure and gastrointestinal bleeding.