Potential impact of obligatory use of opioids in invasive procedures on interpretation of experimental data

Abstract

Application of opioids as an analgesic drug is a common practice in the prevention of pain in patients and experimental animals in highly invasive procedures. Very recently, new legal regulations were implemented that broaden the application of analgesics in procedures where pain relievers have not been previously obligatory. However, in light of hitherto studies, the application of opioids has adverse effects on the condition of animals in experiments. Harmful effects of opioids include: lower intake of water and food, weight loss, increased mortality, susceptibility to infection by experimental pathogens and chemicals inducing pathological changes. The above listed actions, induced by opioids, may significantly affect interpretation of experimental data. The aim of this article is to review selected studies in animal models, mainly on the application of morphine and buprenorphine, including the mechanism of opioid action. Alternative methods of analgesia, involving other types of pain relievers, such as non-steroid anti-inflammatory drugs, are also described. Since opioids significantly affect the values of investigated parameters, some experimental procedures should be probably modified in order to lower the detrimental effects of this class of pain relievers. In consequence, new protocols would probably consider the application of lower doses of compounds or pathogens required for the induction of defined, experimentally induced disease states. A wider application of analgesics, of a different mechanism of action than opioids, would also be an alternative.