How can we diagnose pure opium overdose cases in retrospective medical chart reviews?

American Journal of Emergency Medicine

We are grateful for the interest in our article “Brain computed tomographic scan findings in acute opium overdose patients” . In retrospective studies, such as ours, some limitations are inevitable. For instance, exclusion of the multidrug exposures based on the history is one of them that has been mentioned as the most important limitation of our study in the “Discussion.” Regarding the use of toxicology screening for exclusion of other substances of abuse, it should be mentioned that each drug of abuse screening test may exhibit a different cross-reactivity profile. Depending on this profile, drug abusers may have false-positive or false-negative results . Furthermore, in drug screens, some substances of abuse cross-react with other medications . Therefore, with these limitations, the results of such screening tests may sometimes create confusion except for when they are confirmed by retesting using a nonimmunologic test . In addition, the major problem with opiates is that several opiates are metabolized into each other. For example, morphine is a metabolite of codeine and heroin as well as a constituent of opium. So, heroin exposure cannot be distinguished from opium exposures using such screening tests. In addition, synthetic opioids are often not detected by these tests. With respect to the aforementioned points, even if few patients' samples were sent to perform toxicology screening tests and reports of their results were available in the files, these results would not be valuable for the inclusion or exclusion of the cases. However, attention to the following points shows that our results and conclusion are reliable: (1) Opium overdose is very common in our country . (2) In addition to the history, diagnosis of the isolated opium overdose cases in medical charts has been made based on clinical manifestations that are different from overdose with other non-opioid abused drugs. (3) Cocaine and crack cocaine abuse is rare in Iran. (4) Although acute overdose by amphetamines, methamphetamines, and ecstasy is not so uncommon in our country , of the most common—if any—findings of their overdose similar to that of cocaine are subarachnoid or intracerebral hemorrhages, which were not detected in none of our cases . (5) Cannabis is one of the most commonly abused drugs in our community . However, the relation of ischemic strokes with its overdose has not yet been established . (6) In addition to other exclusion criteria that have been mentioned in our article, some cases of previously diagnosed structural changes on brain computed tomographic scan were also found that were not included. These were cerebral palsy, arteriovenous malformations, cerebral atrophies, previous surgeries on the brain, brain tumors, and previous cerebrovascular accidents. Thus, we believe that, in communities with high frequency of opium abuse, our results can surely be applicable in the clinical practice.