Adjuncts to Anesthesia: Ketorolac

KETOROLAC

Mechanism of Action

Ketorolac is a parenteral nonsteroidal antiin-flammatory drug (NSAID) that provides analgesia by inhibiting prostaglandin synthesis.

Clinical Uses

Ketorolac is indicated for the short-term (<5 days) management of pain, and appears to be particularly useful in the immediate postoperative period. A standard dose of ketorolac provides analgesia equiv-alent to 6–12 mg of morphine administered by the same route. Its time to onset is also similar to mor-phine, but ketorolac has a longer duration of action (6–8 h).Ketorolac, a peripherally acting drug, has become a popular alternative to opioids for postop-erative analgesia because of its minimal central ner-vous system side effects. Specifically, ketorolac does not cause respiratory depression, sedation, or nau-sea and vomiting. In fact, ketorolac does not cross the blood–brain barrier to any significant degree. Numerous studies have shown that oral and paren-teral NSAIDs have an opioid-sparing effect. They may be most beneficial in patients at increased risk for postoperative respiratory depression or emesis.

Side Effects

As with other NSAIDs, ketorolac inhibits platelet aggregation and prolongs bleeding time. It and other NSAIDs should therefore be used with caution in patients at risk for postoperative hemorrhage. Long-term administration may lead to renal toxicity (eg, papillary necrosis) or GI tract ulceration with bleed-ing and perforation. Because ketorolac depends on elimination, it should not be given to patients with kidney failure. Ketorolac is contraindicated in patients allergic to aspirin or NSAIDs. Patients with asthma have an increased incidence of aspirin sensi-tivity (approximately 10%), particularly if they also have a history of nasal polyps (approximately 20%).

Dosage

Ketorolac has been approved for administration as either a 60 mg intramuscular or 30 mg intravenous loading dose; a maintenance dose of 15–30 mg every 6 h is recommended. Elderly patients clear ketorolac more slowly and should receive reduced doses.

Drug Interactions

Aspirin decreases the protein binding of ketoro-lac, increasing the amount of active unbound drug. Ketorolac does not affect minimum alveolar con-centration of inhalation anesthetic agents, and its administration does not alter the hemodynamics of anesthetized patients. It decreases the postoperative requirement for opioid analgesics.