IRCT2013102315137N1 IRCT 2014-01-28 Arak University of Medical Sciences, Vice Chancellor for Research Comparison of the effects of ondansetron and ketamine on spinal anesthesia-induced hypotension in women undergoing cesarean section Comparison of prophylactic effect of ondansetron and ketamine on spinal anesthesia-induced hypotension in cesarean section 2013-07-23 anticipated 93 Complete https://irct.ir/trial/14506 interventional Randomization: Randomized, Blinding: Double blinded, Placebo: Used, Assignment: Parallel, Purpose: Prevention, Other design features: Injecting person, and the person responsible for collecting data are not aware of injecting drug. Syringes containing drug are prepared by someone else and are only labeled by the letters A, B, and C. 2 Hypotension. Intervention 1: Intervention 1. Ondansetron, 4 milligrams (2 ml), slow IV injection in 30 seconds; made in Tehran Chemistry Pharma Co. with chemical composition (RS)-9-methyl-3-[(2-methyl-1H-imidazol-1-yl)methyl]-2,3-dihydro-1H-carbazol-4(9H)-one. Intervention 2: Intervention 2. Ketamine, 25 milligrams (volume 2 ml with distilled water), IV injection; made in TRITTAU company, GERMANY, with chemical composition (RS)-2-(2-Chlorophenyl)-2-(methylamino)cyclohexanone. Intervention 3: Intervention 3. Normal saline, 2 ml, IV injection in control group.