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Background: In patients with penetrating eye injury and a full stomach, suxamethonium is still used for rapid sequence induction of anesthesia. But its use is associated with the rise in intraocular pressure (IOP) and this can result in permanent vision loss in these patients. Dexmedetomidine and clonidine are two alpha-2 adrenergic agonist drugs which prevent the rise in IOP. The aim of this study is to compare the efficacy of intravenous (i.v.) dexmedetomidine and clonidine in preventing an increase in IOP after administration of suxamethonium and tracheal intubation. Materials and Methods: Sixty patients undergoing elective nonophthalmic surgery under general anesthesia were included in this clinical study. Patients were randomly assigned into three groups to receive 0.5 mcg/kg dexmedetomidine (Group D), 2 mcg/kg clonidine (Group C) or normal saline (Group S) as premedication i.v. over a period of 10 min before induction. IOP, heart rate, and mean arterial pressure were recorded before and after premedication, after suxamethonium, after intubation and then after 5 min. Results: Following administration of dexmedetomidine and clonidine IOP decreased in both groups. After suxamethonium IOP increased in all three groups but it never crossed the baseline in Group D and C. After laryngoscopy and intubation IOP again increased in all three groups but in dexmedetomidine group it never crossed the baseline whereas in clonidine group it was significantly higher than the baseline. Conclusion: Single i.v. dose of dexmedetomidine premedication (0.5 mcg/kg) blunt the IOP and hemodynamic response to suxamethonium injection and tracheal intubation more effectively than single i.v. dose of clonidine premedication (2 mcg/kg). [ABSTRACT FROM AUTHOR]