Evaluation of the Analgesic Effects of Teucrium Extract on Rats using the Formalin Test

Pain is the most frequent symptom in different diseases. In modern medicine, there are two main categories of analgesics: opioids and non-steroidal anti-inflammatory drugs (NSAIDs). Given the importance of medicinal plants in the treatment of different diseases, this study aimed to compare the analgesic effects of the alcoholic extract of Teucrium with morphine and aspirin. In this experimental study, 36 Wistar rats were randomly divided into six groups of 6. The negative control group received normal saline (5 ml/kg), two positive control groups received morphine 2.5 mg/kg and aspirin 300 mg/kg, and three treatment groups received hydro-alcoholic extract of Teucrium (100, 200 and 400 mg/kg) intraperitoneally in single doses. Half an hour after the intraperitoneal injection of the extract, 50 microlitres of 2.5% formalin was injected subcutaneously into the right paw of the rats, and the analgesic effects were compared using the formalin test. In this study, the hydro-alcoholic extract of Teucrium had a dose-dependent analgesic effect, and the most effective dose of the extract was 200 mg/kg. Acute pain scores in the normal saline, aspirin, morphine and 200 mg/kg extract groups were 2.58±0.09, 1.39±0.06, 4.15±0.09 and 1.61±0.1, respectively. In addition, chronic pain scores were 2.37±0.09, 0.99±0.1, 0.33±0.09 and 1.18±0.06, respectively. Analgesic effects of Teucrium extract on chronic pain were lower compared to morphine, and had no significant difference with aspirin. According to the results of this study, and regarding the presence of polyphenolic compounds in this herb, Teucrium is believed to have several analgesic properties.