You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Outcome", "Participant", "Intervention"].

Please return the output as a JSON object of the format: {"Participant" : ["patients with COPD", ...], "Intervention" : ["Atenolol", ...], "Outcome" : ["blood pressure", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

Randomized double-blind , placebo-controlled evaluation of oral ondansetron in the prevention of nausea and vomiting associated with fractionated total-body irradiation . PURPOSE To evaluate oral ondansetron in the prevention of total-body irradiation ( TBI ) -induced nausea and vomiting . METHODS Twenty patients who received 4 days of TBI as part of their preparative regimen before bone marrow transplantation were randomized to receive either 8-mg oral doses of ondansetron or placebo . Administration of drug was double-blinded . Initial rescue therapy consisted of intravenous ( i.v . ) ondansetron 0.15 mg/kg following two or more emetic episodes between successive fractions of TBI or five total emetic episodes during the 4 days of therapy . If , after receipt of i.v . ondansetron , patients had two or more emetic episodes between fractions of TBI or five total emetic episodes , additional antiemetics were administered . RESULTS Patients who received oral ondansetron had significantly fewer emetic episodes compared with those who received placebo ( P = .005 ) over the entire 4-day study period . Oral ondansetron was also significantly superior to placebo with respect to the time of onset of emesis or rescue ( P = .003 ) . Six of 10 patients treated with oral ondansetron completed the study without additional antiemetic therapy , while none of 10 patients who received placebo completed the study without rescue antiemetic therapy . Six placebo patients who received initial rescue therapy with i.v . ondansetron required no additional antiemetics . No relationships were apparent between peak ondansetron concentration ( Cmax ) or area under the concentration versus time curve ( AUC ) and number of emetic episodes . CONCLUSION Oral ondansetron is an effective therapy for the prevention of emesis induced by TBI .
{"Intervention": ["placebo", "antiemetic therapy", "oral doses of ondansetron", "oral ondansetron", "initial rescue therapy", "placebo-controlled", "ondansetron", "Oral ondansetron"], "Outcome": ["time of onset of emesis or rescue", "additional antiemetics .", "rescue antiemetic therapy .", "peak ondansetron concentration ( Cmax ) or area under the concentration versus time curve ( AUC ) and number of emetic episodes .", "emetic episodes"], "Participant": ["total-body irradiation ( TBI ) -induced nausea and vomiting", "vomiting", "nausea", "Twenty", "fractionated total-body irradiation"]}