Ketorolac for postoperative pain management in children

Abstract

Ketorolac is a nonsteroidal anti-inflammatory drug (NSAID) with potent analgesic effects and a relatively low incidence of adverse effects. Numerous clinical trials of postoperative pain treatment in children have shown that ketorolac is as effective as the major opioid analgesics, such as morphine, and more effective than codeine. The pharmacokinetics of ketorolac differ in children compared with adult patients after surgery. In children, the volume of distribution (Vd) of ketorolac is increased by as much as 2-fold relative to that in adults. The plasma clearance (CL) of ketorolac is also higher in children, probably because of lower binding to plasma proteins. However, the elimination half-life (t 1/2 beta) of ketorolac is similar in children and adults because t 1/2 beta is directly proportional to Vd but inversely proportional to CL. These pharmacokinetic differences indicate that a higher relative dosage is required in children, but the dosage interval is similar in children and adults. Ketorolac can be administered intravenously, intramuscularly or orally. The intravenous route is preferred during the immediate postoperative period, until the patient can tolerate oral medication. Intramuscular injections are not recommended in children, unless the intravenous route is unavailable. The recommended intravenous dosage of ketorolac in children is 0.5 mg/kg, followed either by bolus injections of 1.0 mg/kg every 6 hours or an intravenous infusion of 0.17 mg/kg/h. The maximum daily dosage is 90mg, and the maximum duration of treatment is 48 hours. The recommended oral dosage is 0.25 mg/kg to a maximum of 1.0 mg/kg/day, with a maximum duration of 7 days. Older children may require somewhat lower dosages, while infants and young children may require slightly higher dosages to achieve the same level of pain relief. Ketorolac is not recommended for use in infants aged < 1 year. Unlike opioid analgesics ketorolac does not depress ventilation, and is not associated with nausea and vomiting, urinary retention or sedation. When combined with an opioid, ketorolac exhibits marked opioid-sparing effects, allowing a lower dosage of opioid to be used. Clinical studies in children and adults show that the synergistic action of ketorolac and opioids improves the degree and quality of pain relief, and reduces the incidence of opioid-related adverse effects such as respiratory depression, nausea/vomiting and ileus. Recovery of bowel function after abdominal surgery occurs sooner in ketorolac-compared with opioid-treated patients. Ketorolac reversibly inhibits cyclo-oxygenase, and decreases the hypersensitisation of tissue nociceptors that occurs with surgery. It also has reversible antiplatelet effects, which are attributable to the inhibition of thromboxane synthesis. Bleeding time is usually slightly increased, but in most patients it remains within normal values. There is conflicting evidence of the potential for increased surgical-site bleeding after tonsillectomy but, for other types of paediatric surgery, numerous clinical studies have confirmed that ketorolac is not associated with increased bleeding. Thus, ketorolac is well suited for the treatment of postoperative pain in children, either alone or in combination with opioids or local anaesthetics, because of its analgesic potency and relatively low incidence of adverse effects.