Background: Tincture of opium (TOP) is currently used for maintenance therapy in treatment of opioids addiction. It contains ethanol. The present study was conducted to assess the increase in blood alcohol concentration (BAC) in its users; a process which may interfere with breath-alcohol test performed by law enforcement or traffic police. Methods: A total of 143 individuals were selected randomly from drug users who had been referred to an addiction treatment clinic. They were asked to undergo breath-alcohol test 15, 30, 45, and 60 min after taking their daily dosage of TOP. The resulting figures were statistically analyzed by t-test and chi-square test using SPSS for Windows. Findings: The calculated blood ethanol concentration rose to 26.33 ± 14.34, 29.15 ± 6.70, and 33.03 ± 8.46 in persons taking 20, 25, and 30 ml TOP respectively, 5 min after their drug ingestion. The figures turned into zero after 15 min. Conclusion: Users of TOP should be reassured about its alcoholic content. Its alcoholic content cannot produce equilibrium disturbance or notable BAC. However, it is recommended that users of TOP are observed in addiction treatment centers for 15 min after taking their drug to reach a higher degree of certainty about any effect of alcoholic content of TOP.