The effect of opium alkaloids is modified by promethazine added to “compote” by drug addicts. Promethazine as an additive to poppy straw extracts enhances the effect of intoxication; facilitates the self-administration of the narcotic in an intravenous or intramuscular injection; and reduces the adverse effects of opiates through its cholinolytic, antihistamine, and antiemetic activity. The study found that under conditions of acute exposure to xenobiotics, promethazine-enriched poppy straw extract exhibited a higher toxicity than nonenriched poppy straw extract, due to the synergistic effect of opiates and promethazine in their depressing effect on the central nervous system. Promethazine supplementation is the reason for changes that occur in absorption and elimination of morphine, monoacetylmorphine, and codeine, enhancing the intoxicating and toxic activity of the narcotic. The authors used poppy straw extracts supplied as evidence in drug offenses. Initially, the LD50 dose of acute intraperitoneal toxicity for poppy straw extracts with (kp) and without promethazine supplementation (k) was calculated with reference to morphine. Based on blood analysis of rats divided into groups administered “k” and “kp,” extracts at a dose of 1/2LD50, as well as a dose of standard morphine with concentration corresponding to that in the extract (8.56 mg/ml 0.9 percent sodium chloride), basic toxic kinetic parameters of the opiates were determined. Identification and quantitative examination of morphine, codeine, monoacetylmorphine, papaverine, narceine, and promethazine were performed with high performance liquid chromatography/mass spectrometry. 8 tables, 7 figures, and 14 references