Evaluations of echogenicity in gluteal muscle in patients with schizophrenia treated with second generation long-acting injectable antipsychotics: risperidone or aripiprazole

Second generation long-acting injectable antipsychotics (SG-LAIs) injected muscle region show high-echogenicity with acoustic shadowing on B-mode scan. This study aimed to distinguish two specific types of SG-LAIs at the gluteal muscle. Forty-seven patients [risperidone (RLAI): 28 patients, aripiprazole (ALAI): 19 patients] were examined using grayscale histogram analysis of echo-intensities. Pre- and immediately after (post)-injected SG-LAI region of interest (ROI) was placed on the same sites of gluteal muscle, and the grayscale histograms were recorded. Pre- and post-injected echogenicity values were analyzed using paired t-test, and Pearson’s moment correlation coefficient. Mixed effects model regression analysis was performed on variations in average echogenicity from age and medication type. Statistical significance was at 5%. There was no significant correlation between age and average echogenicity of ROI pre-intramuscular (IM) injection (r = 0.26, p = 0.078). In both RLAI and ALAI, the mean echogenicity post-IM injection was significantly higher than pre-IM injection (p < 0.001). With increasing age, the values of echogenicity of post-injection was decreased significantly (p = 0.002). The increasing values of the echo-intensities post-injections of RLAI showed significantly higher than ALAI (p = 0.002). It was considered that administered type of LAI could be identified because each LAI exhibits specific echographically findings, it also will be able to applied clinically.