To evaluate the effect of oral amantadine versus gabapentin premedication on the hemodynamic response to laryngoscopy and tracheal intubation and their effect on β-endorphins.

Direct laryngoscopy and passage of endotracheal tube through the larynx is a noxious stimulus, which can provoke untoward response in the cardiovascular, respiratory and other physiological systems. Gabapentin, is 1-aminomethyl cyclohexane acetic acid.Gabapentin is structurally related to the neurotransmitter gamma-aminobutyric acid (GABA). Gabapentin act in central nervous system CNS), it acts by decreasing the synthesis of neurotransmitter glutamate and by binding to the alpha 2 delta subunits of voltage dependent calcium channels.

Amantadine is a non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, and compared to ketamine, it is well tolerated with fewer side effects (mainly dizziness, sedation, and dry mouth). Amantadine's formulation permits the oral route for drug delivery, as well as the IV route. The side-effects profile of amantadine via all routes seems not to be harmful in appropriate dosages.. Amantadine has been clinically used as an antiviral drug, for dementia, and in the treatment of Parkinson's disease and spasticity. It is a non-competitive NMDA receptor antagonist, and compared to ketamine, it is well tolerated with fewer side effects (mainly dizziness, sedation, and dry mouth). Amantadine's formulation permits the oral route for drug delivery, as well as the IV route. The side-effects profile of amantadine via all routes seems not to be harmful in appropriate dosages.

In the central nervous system, beta-endorphins bind mu-opioid receptors and exert their primary action at presynaptic nerve terminals. However, instead of inhibiting substance P, they exert their analgesic effect by inhibiting the release of GABA, an inhibitory neurotransmitter, resulting in excess production of dopamine.

The investigators designed this study to prove the efficacy of oral amantadine versus gabapentin premedication on the hemodynamic response to laryngoscopy and tracheal intubation and their effect on β-endorphins.

Inclusion Criteria:

• ASA I&II scheduled for elective spine surgery

Exclusion Criteria:

• Patient refusal
• Patients with ASA score III (with chronic kidney, lungs, Gastrointestinal tract, liver, or cardiovascular diseases)
• Pregnant or breastfeeding women.
• Allergy to any of the study medications and taking medications that could significantly interact with amantadine (tramadol, atropine, antipsychotic medications)
• diabetes mellitus, thyroid disease any endocrine disease
• Suspected difficult intubation or intubation time more than 30 second.