OBJECTIVES: Patients presenting to the emergency department (ED) with suspected biliary colic often require intravenous (IV) analgesia. The choice of IV analgesia typically includes opioids and ketorolac. Although ultrasound (US) is the initial diagnostic study in these patients, nondiagnostic scans and a high clinical suspicion may require the patient to undergo hepatobiliary scintigraphy (HIDA). Opioids such as morphine interfere with the HIDA scan and thus may limit its value as an analgesic in the ED for these patients. Analgesics that do not interfere with HIDA scanning include ketorolac and butorphanol, an opioid agonist-antagonist. This study evaluates the efficacy of IV ketorolac compared to butorphanol for the treatment of biliary colic pain in the ED. METHODS: Between June 2005 and February 2007, a convenience sample of patients presenting to the ED with abdominal pain suspected to be biliary colic were randomized to receive either 30 mg of IV ketorolac or 1 mg of IV butorphanol. Pain level was assessed using a 1 to 10 "faces" visual analog pain scale initially, as well as 15 and 30 minutes after medication infusion. Side effect profiles and the need for rescue analgesia were also assessed. Patients and clinicians were blinded to the study drug given. RESULTS: Forty-six patients were enrolled in the study. Both groups had similar demographics and baseline pain scores. The mean (+/-standard deviation [SD]) pain score in the butorphanol group decreased from 7.1 (+/-1.7) to 2.1 (+/-2.2) after 30 minutes. The mean (+/-SD) pain score in the ketorolac group decreased from 7.4 (+/-2.0) to 3.1 (+/-3.3) after 30 minutes. Both groups had similar needs for rescue analgesia. Side effects included dizziness and sedation with butorphanol and nausea with ketorolac. CONCLUSIONS: Although limited by small sample size and convenience sample, this study demonstrates that both ketorolac and butorphanol provide pain relief in biliary colic. Both agents should be considered reasonable options in the ED treatment of biliary colic, especially in patients that may undergo HIDA.