RESUMEN
Introduction: Parthenium hysterophorus is an aggressive ubiquitous annual herbaceous weed with no economic importance unravelled till now. The decoction of P. Hysterophorus has been used in traditional medicine to treat fever, diarrhoea, neurologic disorders, urinary tract infections, dysentery, malaria and as emmenagogue. Objective: The study was conducted to screen the antipyretic activity of hydro-alcoholic extracts of Parthenium Hysterophorus. Materials and Methods: Thirty healthy rats weighing between 200-250gms were divided into five groups of six animals each, with 50% sex ratio. The initial rectal temperature of each animal was recorded by digital thermometer. The pyrexia was induced by injecting 20ml/kg (s.c.) of 20 per cent aqueous suspension of Brewer’s yeast in normal saline below the nape of the neck and rectal temperature was recorded by clinical thermometer immediately before (18 h) and 18 h after (0 h) Brewer’s yeast injection .The difference in temperature between 0 hour and respective time interval was found out by statistical method. The potency of extract to bring down the temperature was compared with that of the control group. Results: PH extract at 200 and 400 mg/kg produced significant antipyretic activity at 1 h after drug administration, whereas PH extract (800 mg/kg) and aspirin(300 mg/kg) showed significant antipyretic activity throughout the observation period up to 6 h. The extract showed marked antipyretic activity in a dose dependent manner. Conclusion: Parthenium hysterophorus has marked antipyretic activity.