Comparative analgesic effects of paracetamol with paracetamol-caffeine formulation

Abstract

This study was designed to evaluate the contribution of caffeine to analgesia in paracetamol-caffeine preparation. Analgesic properties were evaluated in mice using acetic acid-induced writhing and hot plate methods. In the acetic acid method, the test drugs were administered orally to the mice. After 30 min. all the mice received 0.7% aqueous solution of acetic acid (10ml/kg i.p) and writhing was counted for 30 min. after acid injection. The percentage inhibition was then determined. In the case of hot plate method, the mice were placed singly on a hot plate maintained at 45±0.50C before and at 15, 30, 45, 60 and 90 min. after administration of the tested drugs orally. The latency of nociceptive responses (time taken before the mouse jumped out of the hot plate) was measured each time the mouse was placed on the hot plate. The mean percentage maximum possible effect (% MPE) was determined. The results revealed dose dependent analgesic activities in both paracetamol alone and paracetamol-caffeine combination. The activities were significantly higher compared to the control which received normal saline (p<0.05). There was a sharp increase in activity between 15-30mins by paracetamol-caffeine combination, with maximum activity setting in as from 30mins. But paracetamol alone had maximum effect at 45mins. It could be concluded that caffeine could enhance analgesic activity of paracetamol. However further pharmacokinetics and pharmacodynamic evaluations are needed to strengthen this view.

Journal of Pharmacy & Bioresources Vol. 2(2) 2005: 65-69