The toxicological interpretation of blood and urine concentrations of drugs affecting the digestive system and metabolism, as with other groups of pharmaceutical specialties, is complicated. As a continuation of our published studies on the concentrations of drugs of abuse, drugs affecting cardiovascular and hematopoietic systems, and respiratory system, we have reviewed the published data relating to the concentrations of drugs affecting the digestive system and metabolism in clinical and forensic cases. We have selected them on the basis of conservative criteria and our own experience. A table with concentrations of 101 drugs in whole blood, serum/plasma, and urine, corresponding to therapeutic, toxic, or lethal concentrations, is presented. The data can help interpret analytical results of patient or postmortem samples when there is a suspicion of poisoning with this group of drugs.