Parenteral buprenorphine-naloxone abuse is a major cause of fatal buprenorphine-related poisoning.

Buprenorphine (BPN) medication for opioid maintenance treatment in Finland consists predominantly of buprenorphine-naloxone (BNX). Both BPN and BNX are associated with diversion, abuse and non-medically supervised use worldwide. Our purpose was to estimate the proportion of BNX to all BPN-related fatalities. The material consisted of 225 deceased drug abusers in Finland from January 2010 to June 2011 with a positive BPN and/or norbuprenorphine (NOR) and/or naloxone (NX) finding in urine. The data were divided into three groups based on the urine NX and BPN concentrations. The "Parenteral BNX" group (>100 μg/l NX) was presumed to consist of injecting or snorting BNX abusers and the "Parenteral BPN" group (>50 μg/l BPN, 0 μg/l NX) of injecting or snorting BPN abusers, while the "Other BNX or BPN" group (≤100 μg/l NX, or ≤50 μg/l BPN combined with 0 μg/l NX) was presumed to consist of mainly sublingual BNX or BPN users. In 12.4% of cases the NX urine concentration was higher than the threshold 100 μg/l. In fatal BPN poisonings, the proportion of parenteral BNX was 28.4%. In the "Parenteral BNX", "Parenteral BPN" and "Other BNX or BPN" groups, the proportion of fatal BPN poisonings was 67.9, 31.0 and 22.6%, respectively. BNX abuse can be fatal. Among the 225 BPN-related fatalities, parenteral abuse of BNX was shown to be common (12.4%) and BNX poisoning was the underlying cause of death in 8.4%. Parenteral BNX caused fatal BPN poisoning proportionally more often than parenteral BPN.