Evaluation the Efficacy of Intrathecal injection of Amitryptiline and Doxepin in Spinal Anesthesia and in comparison with Bupivacaine in Rats

Nowadays tricyclic antidepressants (TCAs) are commonly used orally for treating chronic pain states، such as neuropathic pain. TCAs produce analgesia by various mechanisms involving Sodium channels، N-methyl-d-aspartate receptors، biogenic amines، opioids، inflammatory mediators، and substance P. Studies have shown that intrathecal tricyclic administration effectively attenuates pain and thermal hyperalgesia in inflammatory and neuropathic pain in rats. In a double blind RCT study in animal lab intathecal injection of drugs performed in 30 Wistar male rats. They devided in 3 groupes. In G1، 90 μl Doxepine (50 mM)، G2، 90 μl amitriptyline (60mM) and in G3، 90 μl bupivacaine (23 mM) was injected. Then sensory، motor and proprioceptive changes was measured in these hours: 1، 2، 3، 4، 6 and 12 by one examiner Three rats died in G1 and G2. After adjusting the influences from different concentrations، amitriptyline had a similar potency but a longer duration of spinal blockade of motor، propioception، and nociception than did bupivacaine (p value<0. 05). Whereas doxepine had a reasonable but lower efficacy and shorter duration of spinal blockade than did bupivacaine (P value<0. 05). The full recovery times for G2 were significantly longer. Conclussion: It seems that tertiary amine drugs such as amitriptyline and doxepin، had reasonable potencies of spinal blockade when compared to bupivacaine. But amitriptyline has a more potent and long-acting spinal anesthetic effect. It may turn to be a clinical valuable local anesthetic.