We present an unusual case of suicide by intraperitoneal injection of pentobarbital, an overdose of zolpidem and the intake of diazepam, ethanol and other psychoactive substances. The autopsy and specimen collection were conducted in a 10 to 18 h postmortem interval. The toxicological analysis revealed a significantly higher pentobarbital concentration in femoral blood compared to cardiac blood (36 vs. 15 mg/L). On the contrary, zolpidem and diazepam concentrations in cardiac blood (2700 and 590 µg/L) were found to be significantly higher than in femoral blood (1500 and 230 µg/L). These findings point to a postmortem redistribution with a distinct gradient from areas of high drug concentrations in the gastrointestinal tract (zolpidem and diazepam) and the injection site (pentobarbital) to peripheral tissue. Ethanol concentration was 0.95 ‰ which amplified the CNS depression. The choice of this unusual suicide method was associated with the deceased’s former job as a veterinarian’s assistant. In veterinary medicine, the intraperitoneal injection of a lethal dose of pentobarbital is quite commonly performed to euthanise small animals. Intraperitoneal injection is rare as route of administration in humans.