A case of diphenhydramine intoxication showing prolonged false positive tricyclic antidepressant in the urine assay

• Published in: Asian biomedicine 2023-02, Vol.17 (1), p.39-42
• Main Authors: Kim, Dongsun, Shin, Hyun Young, Ku, Bon D.
• Format: Article
• Language: English
• Subjects: ataxia; Clinical Vignettes; cross reactivity; diphenhydramine; tricyclic antidepressants; urine immunochromatographic assay
• ISSN: 1875-855X; 1905-7415; 1875-855X
• DOI: 10.2478/abm-2023-0042

The urine immunochromatographic assay is a useful screening tool for patients suspected of acute drug intoxication in emergency conditions. Diphenhydramine intoxication shows symptoms similar to those of tricyclic antidepressant (TCA) intoxication.BackgroundThe urine immunochromatographic assay is a useful screening tool for patients suspected of acute drug intoxication in emergency conditions. Diphenhydramine intoxication shows symptoms similar to those of tricyclic antidepressant (TCA) intoxication.We examined a case of diphenhydramine intoxication showing cerebellar ataxia and prolonged false positive results for TCA in the urine. The urine TCA test showed persistently positive results even 60 h after the patient's initial drug screening. We observed negative conversion 90 h after the initial drug screening.Case presentationWe examined a case of diphenhydramine intoxication showing cerebellar ataxia and prolonged false positive results for TCA in the urine. The urine TCA test showed persistently positive results even 60 h after the patient's initial drug screening. We observed negative conversion 90 h after the initial drug screening.Considering the similarities of clinical symptoms between diphenhydramine and TCA intoxication, emergency physicians should consider the possibility of cross-reactivity in the diagnosis of a patient with unknown acute drug intoxication showing positive results of TCA immunochromatographic assay in the urine.DiscussionConsidering the similarities of clinical symptoms between diphenhydramine and TCA intoxication, emergency physicians should consider the possibility of cross-reactivity in the diagnosis of a patient with unknown acute drug intoxication showing positive results of TCA immunochromatographic assay in the urine.The present case suggests that diphenhydramine overdose may cause cerebellar ataxia and show prolonged cross-reactivity as TCA in the urine.ConclusionThe present case suggests that diphenhydramine overdose may cause cerebellar ataxia and show prolonged cross-reactivity as TCA in the urine.