Flunitrazepam tablets contain Brilliant Blue FCF（FD&C Blue No. 1）as an abuse-deterrent additive and produce intense blue discoloration when crushed and dissolved. We report a case mimicking acute arterial occlusion after injection of a flunitrazepam solution. A man in his 30s presented after injecting a tap-water solution prepared from half of a 2-mg flunitrazepam tablet into the dorsum of his right hand. Approximately eight hours later, he developed finger pain and bluish-purple discoloration. Pulse oximetry failed to obtain SpO2 readings. On the ultrasonic blood-flowmeter, doppler signals were present in the radial and ulnar arteries and dorsal metacarpal arteries, but absent in the dorsal digital arteries bilaterally. Contrast-enhanced CT showed no arterial occlusion, and capillary refill, motor, and sensory function were preserved. Non-operative management led to improvement. FD&C Blue No. 1 likely caused ischemia-like findings. Careful differentiation from true acute arterial occlusion is essential to avoid unnecessary invasive treatment.
