Evaluation of Analgesic Activity of Standardised Aqueous Extract of Withania somnifera in Healthy Human Volunteers using Mechanical Pain Model

Introduction: Drugs commonly used for pain management are associated with adverse effects. Experimental pain models in human healthy volunteers are advantageous for early evaluation of analgesics. Studies with Withania somnifera have demonstrated that it possess anti-inflammatory, analgesic, antioxidant, immunomodulatory properties by virtue of its active constituents. Aim: To evaluate safety and analgesic activity of single oral dose (1000 mg) of Withania somnifera using mechanical pain model in healthy human subjects. Materials and Methods: This randomised, double-blind study was approved by the IEC and was conducted in healthy volunteers after obtaining informed consent from the participants. Volunteers were randomly given either placebo or Withania somnifera capsules (1000 mg). Mechanical pain was assessed using Randall Selitto before and three hours after test drug administration. Pain threshold force and time and pain tolerance force and time were evaluated. A washout period of 10-14 days was given for cross over between two medications. Results: Pain threshold force with Withania somnifera increased from 450.29±75.49 grams to 538.5±72.27 grams (p=0.003) and pain threshold time increased from 5.63 seconds to 6.73 seconds (p=0.003). Further Withania somnifera increased pain tolerance force from 806.9±61.36 grams to 878.2±82.6 grams (p=0.002) and pain tolerance time increased from 10.09 seconds to 10.97 seconds (p=0.002). No statistical significant increase was observed with placebo. Conclusion: In the present study, Withania somnifera significantly increased pain threshold force and time and also pain tolerance force and time compared to placebo. Test drugs were well tolerated. Further studies may be needed in patients suffering from pain conditions (osteoarthritis, rheumatoid arthritis) who require analgesics.