Cross-Reactivity of Naloxone with Oxycodone Immunoassays: Implications for Individuals Taking Suboxone®

Abstract

In 2002, the US Food and Drug Administration approved the use of the sublingual tablet, Suboxone® (Reckitt Benckiser Pharmaceuticals), to treat opioid dependence. The formulation is available at 2 doses, 2 or 8 mg (free base) buprenorphine hydrochloride and 0.5 or 2 mg (free base) naloxone hydrochloride dihydrate (1). The combination product is designed to decrease the potential for intravenous abuse, since parenteral administration may precipitate opioid withdrawal(2). To monitor compliance, physicians request urine testing of buprenorphine and often additional testing to ensure no illicit drug use. A client recently requested multianalyte testing of patients taking Suboxone. Initial testing suggested a response with the oxycodone assay. We hypothesized this response was due to the presence of naloxone. To test this hypothesis, we ( a ) assayed a 40-μg/L buprenorphine calibrator with the oxycodone assay and ( b ) assayed drug-free urine samples that had been supplemented with increasing concentrations (100–10 000 μg/L of naloxone (Cerilliant Corporation) and naloxone glucuronide (Sigma–Aldrich). We evaluated 2 enzyme immunoassays: the homogeneous enzyme immunoassay (HEIA) oxycodone (Immunalysis Corporation) and the DRI® …