Background: Renal colic causes excruciating pain that provides a good clinical model of acute pain for the development of new analgesics.
Objective: The purpose of the study was to compare the analgesic efficacy and tolerability of cizolirtine citrate and metamizol sodium in adult acute renal colic.
Methods: This Phase II, randomized, double-blind, clinical pilot study was conducted in the emergency departments of 6 general hospitals in the Czech Republic between October 2000 and February 2001. Male and female patients aged 18 to 65 years and presenting with hematuria and moderate to severe pain due to suspected renal colic starting within the 24 hours before presentation were eligible. Patients were randomized to receive a single IV dose of cizolirtine 350 mg or metamizol 2,500 mg, administered by slow infusion over 15 minutes. Both doses were maximal for the respective drugs to attain adequate analgesia. Use of rescue medication with butorphanol was allowed 30 minutes after study drug administration. Pain intensity was assessed at various time points during the following 360 minutes using a 100-mm visual analog scale (VAS) and a verbal categoric scale. In addition, a specific verbal categoric scale was used to rank pain relief. Physical examinations, laboratory tests, and questioning for adverse events addressed drug tolerability.
Results: Sixty-four patients (50 men, 14 women; mean [SD] age, 44.21 [12.29] years; mean [SD] body mass index, 25.97 [3.38] kg/m(2)) were enrolled. Physical examination findings and mean VAS pain intensity scores at baseline (mean [SD], 79.42 [7.89] mm and 82.59 [10.50] mm in the cizolirtine and metamizol groups, respectively) were similar in both groups. After 30 minutes, the mean (SD) scores were 33.84 (25.15) mm and 25.41 (24.51) mm, respectively. This difference was not statistically significant, and the noninferiority of cizolirtine with respect to the comparator could not be established. However, the proportion of patients that showed satisfactory pain relief (ie, decrease of > or = 50% in VAS pain intensity score compared with baseline) at 30 minutes in the cizolirtine group was fairly high (64.5%), which means relevant analgesic activity. Both treatments were well tolerated; 6 adverse events were reported in 5 patients (7.8%), and all were considered as not treatment related.
Conclusions: Although this limited pilot study did not include an internal measure of sensitivity, relevant pain reduction was shown in the population of patients with suspected renal colic undergoing treatment with cizolirtine, suggesting the presence of analgesic activity. However, the efficacy of cizolirtine was found to be similar to that of metamizol. Treatments were well tolerated.