Fexofenadine cross reactivity with Tramadol drug tests

New Tramadol Fexofenadine cross-reactivity noted

Tramadol is one of the newer developed drug testing membranes on the market. 

Fexofenadine is a modern, non-sedative anti-histamine which is being increasingly being prescribed as a second or third line anti-histamine in the UK.

3 sensitivities are currently on the market for urine drug testing 100, 200 and 300ng/ml

Tramadol is a quasi-narcotic analgesic used in the treatment of moderate to severe pain. its use in the UK has increased rapidly in the last 5 years. Tramadol is a synthetic analog of codeine with low binding affinity to mu-opioid receptors. Large doses result in tolerance and physiological dependency. Tramadol abuse is becoming problematic.

Cross-reactivity testing for Tramadol 

Current datasheet cross-reactivity sets for tramadol are very limited and most current list only Procyclidine as cross-reactive.

Cross-reactivity testing was requested following 3 positive Tramadol tests on a subject prescribed fexofenadine. Confirmation GC/MS results on the 3rd sample were negative.

ALLTEST laboratory biochemists confirmed fexofenadine in concentration over 10ng/ml result in positive urine Tramadol membrane reactivity (false positive) results on point of care test using all sensitivity options


Positive Tramadol near patient test results in donors taking fexofenadine should be confirmed using GC/MS to exclude concurrent tramadol abuse as fexofenadine will result in positive results. GC/MS testing should be negative for Tramadol if the positive near patient test result is solely caused by Fexofenadine.

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