Malaysian Journal of Pharmaceutical Sciences, Vol. 7, No. 2, 113–124 (2009) ANTINOCICEPTIVE AND ANTIINFLAMMATORY PROPERTIES OF THE METHANOL EXTRACT OF URTICA CRENULATA STEM MD. SOHEL RANA 1* , MD. ATIAR RAHMAN 1* , MOHAMMAD MAHBUB-UZ- ZAMAN 2 , MD. ALAMGIR KABIR 2 , HABIBUR R. BHUIYAN 2 AND NAZIM UDDIN 2 1 Department of Biochemistry and Molecular Biology, University of Chittagong, Chittagong-4331, Bangladesh 2 Bangladesh Council for Scientific and Industrial Research (BCSIR), Chittagong, Bangladesh The methanol extract of Urtica crenulata stem was evaluated for its antinociceptive properties on the pain induced by acetic acid and formalin in Swiss albino mice. The methanol extract of U. crenulata at a dose of 1 g/kg produced an inhibition of 32.3% on pain induced by acetic acid and at a dose of 1.5 g/kg produced an inhibition of 31.0% for that induced by formalin. The antiinflammatory activity of the same extract was estimated volumetrically by measuring the mean increase in hind paw volume of carrageenan-induced Wistar albino rat with the help of plethysmometer. Oral administration of stem extract at a dose of 1 g/kg showed no significant effect in the reduction of carrageenan-induced paw oedema. Diclofenac sodium at a dose of 40 mg/kg was used as a standard drug in the inhibition of acetic acid induced pain and carrageenan-induced paw oedema whereas morphine was used as the same in formalin-induced pain inhibition. Keywords: Urtica crenulata, Antinociceptive, Antiinflammatory, Paw oedema, Carrageenan INTRODUCTION Inflammation is a complex biological response of vascular tissues to harmful stimuli, such as pathogens, damaged cells, or irritants that lead to local accumulation of plasmatic fluid and blood cells. It is a protective attempt by the organism to remove the injurious stimuli as well as to initiate the healing process for the tissue (Ferrero-Miliani et al. 2007). In the absence of inflammation, wounds and infections are not healed and progressive destruction of the tissue compromises the survival of the organism. However, an unchecked inflammation can lead to a variety of diseases, such as hay fever, atherosclerosis, and rheumatoid arthritis. Most of the drugs used presently for the management of pain and inflammation possess some side and toxic effects (Ahmad, Khan and * Corresponding author: Md. Atiar Rahman, e-mail: atiarh@yahoo.com