ملخص
Paracetamol is one of the most widely used drug as antipyretic and analgesic for mild to moderate pain. Currently, paracetamol is the first-line choice for pain management and antipyresis. Ion channels are pore-forming proteins that allow the flow of ions across membranes and involved in many cellular processes; drugs acting on ion channels have long been used for the treatment of many diseases. Objective: To estimate the effect of voltage gated ion channel blockers on analgesic activity of Paracetamol and explore the interaction between ion channel blockers and paracetamol on pain behaviour. Materials and Methods: Male albino mice were used. The central antinociceptive activity was determined by hot plate test and formalin test (Phase I; neuropathic pain). Antiinflammatory activity was determined by formalin test (Phase II). Intraperitoneal injection was adopted. Five groups of mice were used. Group 1; control group (1% T80), group 2; treated with (200mg/kg) paracetamol, group 3; treated with different drugs of ion channel blockers, group 4; received standard drugs, Aspirin (200mg/kg) for formalin test (phase II) or tramadol (5mg/kg) for hot plate test and formalin test (phase I), group 5; received combined treatment of ion channel blockers and paracetamol. Results: Pain produced by noxious stimuli (heat and formalin) was significantly reduced by acute administration of paracetamol. Inflammation pain produced by formalin injection was significantly decreased by acute administration of paracetamol. Acute administration of nifedipine showed significant decrease in nociception and inflammation pain. Combined treatment of nifedipine and paracetamol produced antinociceptive and anti-inflammatory activity but less than the additive effect. Verapamil has no analgesic effect in the two models, and did not change the affect of paracetamol analgesic activity when administered together. Phenytoin produces significant decrease in nociceptive pain using hot plate but not in formalin test (Phase I), and produce significant decrease in inflammatory pain (Phase II). The combined treatment of phenytoin and paracetamol showed analgesic activity less than the additive effect. 4-Aminopyridine produces significant antinociceptive and anti-inflammatory activity. The combined administration of 4-aminopyridine and paracetamol showed analgesic activity, which is less than the additive effect using formalin test, while paracetamol analgesic activity is potentiated by 4-aminopyridine using hot plate test. Conclusion: Paracetamol has antinociception and anti-inflammatory activity on pain model used (Hot plate test and Formalin test). Ion channel blockers produce antinociception and anti-inflammatory activity. Verapamil has no effect on nociception or inflammation pain and no effect on paracetamol analgesic activity. Nifedipine, phenytoin and 4-aminopyridine interact with paracetamol producing less additive analgesic effect, except 4-aminopyridine in thermal stimuli (Hot plate) is more sensitive compared to chemical stimuli (formalin test – phase I), where potentiates paracetamol action.