The central effects, tolerability and pharmacokinetics of multiple intravenous doses of the analgesic ketorolac tromethamine (30 mg 4 times daily for 5 days) were studied in male volunteers. In this double-blind, randomized, parallel group study, 13 subjects received ketorolac tromethamine and 7 subjects received placebo (vehicle). To determine the effects of withdrawal all subjects were then given further dosing with placebo (4 times daily) for 2 days while maintaining the double-blind nature of the previous drug assignment. Physical examinations and laboratory tests were obtained prior to the drug administration and after completion of the study. Scales for assessment of anxiety, depression, sleep and opiate withdrawal were presented to the subjects on day 2, 5, 6, 7 and 8 of the study. After 5 days of multiple intravenous doses ketorolac showed overall good systemic tolerance and safety in comparison with placebo. Myalgia and taste perversion were more frequently reported in the ketorolac group. The frequency of injection site complaints, mostly transient pain, was about 80% for both ketorolac and placebo, indicating these were likely caused by the vehicle. There were no significant changes in the scales assessing anxiety, depression, sleep and opiate withdrawal during treatment with ketorolac and after its withdrawal, suggesting that the drug has neither any major central effects nor any clear addiction potential in this dose schedule. Pharmacokinetic parameters were derived from plasma samples collected after the first and last active doses.(ABSTRACT TRUNCATED AT 250 WORDS)