Vomiting , retching , or need for rescue antiemetic treatment at 2 h was reported in 39 of 108 patients assigned to the shorter modified protocol compared with 71 of 109 allocated to the standard acetylcysteine regimen ( adjusted odds ratio 026 , 975 % CI 013-052 ; p < 00001 ) , and in 45 of 109 patients who received ondansetron compared with 65 of 108 allocated placebo ( 041 , 020-080 ; p = 0003 ) .