An in-depth study of the pharmacological properties of 4-[4-oxo-(4h)-quinazolin-3-yl]-benzoic acid as an analgesic agent established that it had a sufficiently high analgesic effect on models of somatic and neuropathic pain syndromes. Study objective was to study the mechanisms of analgesic action of PK-66 compound in rats using the pharmacological analysis. We evaluated the mechanisms of analgesic effect of PK-66 (1 mg/kg, intraperitoneal) compound on the thermal irritation model on Hours 1, 2, 4 and 6 after administration of study compounds. To evaluate the mechanisms of PK-66 compound pain killing, we determined the changes in its efficacy against the effects of pharmacological analyzers - Naloxon, Tramadolum, Clophelinum (Clonidine), Yohimbine, Noraepinephrine, Reserpinum, Chlorpromazine (Aminazin), Levodopa, Diazepam, and Memantine). The anti-nociceptive effect of PK-66 compound was virtually unchanged during all study terms with underlying administration of Naloxon, an opioid receptor antagonist. The results of administration of Reserpinum in rats and the concomitant administration of Noradrenaline, Clophelinum, Yohimbine and quinazoline derivative demonstrated that the adrenergic system, in particular alpha-2 adrenergic receptors, was involved in the mechanisms of PK-66 activity. Changes in the PK-66 compound effect with underlying previous administration of Levodopa and Chlorpromazine suggested that the dopaminergic system was unquestionably involved in the analgesic activity of the compound. Further study of the involvement of inhibitory and exhilarating amino acids, GABA and glutamate, showed that administration of Diazepam potentiated and extended the PK-66 analgesic effect on the thermal nociception models throughout the experiment. At the same time, increased antinociception with underlying Memantine administration preceding PK-66 was observed only in the first hours of the experiment. Therefore, the studies conducted have shown that the adrenergic system, in particular alpha-2 adrenergic receptors, dopaminergic and GABAergic systems, is involved in the mechanisms of analgesic action of 4-[4-oxo-(4h) -quinazolin-3-yl]-benzoic acid (PK-66) without any effect of PK-66 on opioid receptors.