Buflomedil interference with the monoclonal EMIT d.a.u. amphetamine/methamphetamine immunoassay

The interference of buflomedil with the monoclonal and polyclonal EMIT d.a.u. amphetamine immunoassays was investigated. Urine samples collected from 20 patients taking 600 mg of buflomedil daily gave false positive results with the monoclonal EMIT d.a.u. assay, as did urine specimens collected 2 hours after the first oral dose of buflomedil. Conversely, no false positive results occurred with the polyclonal EMIT d.a.u. amphetamine assay. Urine samples with buflomedil added at concentrations greater than 100 mg/l gave false positive results with the monoclonal immunoassay. Buflomedil concentrations found in the patient urines (56-400 mg/l) failed to correlate to EMIT assay responses: this result suggests that one or more buflomedil metabolites, besides the unchanged drug, probably interfere in the monoclonal EMIT d.a.u. assay.