3.5.3 Pharmacology I
Lab 10 Evaluation of Analgesic Action of Narcotic Drug (Tramadol Hcl) on Rats, using tail flick Analgesiometer
Purpose of this experiment is to evaluate the analgesic action of tramadol hydrochloride, using tail flick analgesiometer.
Tramadol, anesthetic codeine analog, is a weak µ-opioid receptor agonist, is used as a centrally acting analgesic alone or in combination with paracetamol. It is prodrug, which is converted to O-desmethyltramadol into the system to produce analgesic action. Tramadol inhibits the reuptake of norepinephrine, serotonin and enhances the release of serotonin. It alters the perception and response of pain by binding µ-opioid receptors in the CNS.
Tablets: 25/50 mg, Extended release tablets: 50/100/150/200/300/400 mg
Capsule: 50 mg, Modified release capsules: 50/100/150/200 mg,
Oral drop: 100 mg/mL, Combined tablet: Tramadol (37.5 mg) + Acetaminophen (325 mg),
Injection: 50 mg/mL, 100 mg/2 mL solution.
Moderate to moderately severe pain postoperative pain, short term treatment of acute pain, labor pain, restless leg syndrome, acid reflux and Fibromyalgia.
Onset of action is 1 hour and duration of action is 3-6 hours for conventional tablets; the peak is 2 hours and the elimination half life is 6-7 hours.
Sprague-Dawley rats (Samtaco, Osan, Korea), weighing 320~450 g, Tail flick Analgesiometer, Timer, Narcotic analgesic (Tramadol HCl: 10 mg/kg B. W.), NS (as control), Needle.
Analgesic effect in rats was assessed by [Dandiya and Menon, 1963] tail flick model, using analgesiometer [Davies et al., 1946]. The tail flick latency was obtained thrice before the administration of the drug, and mean was used as pre drug latency. The tail was placed on the platform in such a way that the middle portion of the tail remained just above the hot wire but without touching it. Radiant heat was directed to the proximal third of the tail through a hot nichrome wire of the analgesiometer. The strength of the current passing through the naked nichrome wire was kept constant at 2-4 Amps. The latency period (reaction time) was noted when the animal responded with a sudden and characteristic flick or tail lifting. A cut off time of 8-10 sec was planned to avoid any tissue damage in the animal. The cut off time was considered when the animals do not respond up to 10 seconds.