Positive interference of the analgesic nefopam in the urine immunoassay for benzodiazepines in a secure setting.
An inpatient on a secure unit with a history of bipolar affective disorder and physical complaints including pain was prescribed carbamazepine, quetiapine, dihydrocodeine, nefopam, paracetamol and various aperients. A benzodiazepine urine test by immunoassay was positive. Initial literature searches did not suggest a candidate drug for positive interference. Other explanations were excluded. Positive results continued, despite room searches and other disruptive security measures. Further literature searches revealed one experimental series demonstrating positive interference of nefopam in the relevant assay. Benzodiazepine assays were negative after cessation of nefopam. This is the first such clinical case to our knowledge.
Reid
K S
KS
Department of Psychiatry, St Nicholas Hospital, Newcastle upon Tyne, UK. k.s.reid@ncl.ac.uk
D018712:Analgesics, Non-Narcotic / Q000652:urine*; D001569:Benzodiazepines / Q000652:urine*; D004353:Drug Evaluation, Preclinical; D006801:Humans; D007118:Immunoassay; D008297:Male; D008875:Middle Aged; D009340:Nefopam / Q000652:urine*
D018712:Analgesics, Non-Narcotic; D001569:Benzodiazepines; D009340:Nefopam