Emesis ED50 of neutron irradiation and prophylactic effectiveness. Final report, 1 January 1979-31 December 1984

Two neutron emesis experiments were conducted at the Armed Forces Radiobiology Research Institute (AFRRI). In both experiments (described as Phase I and Phase II) the radiation dose required to cause emesis in 50% of subjects (ED50) was determined for both neutron reactor and gamma reactor source radiation. Emesis onset, offset and duration times post-exposure are reported. Neutrons were maximized from the reactor by passing the beam through a 15.25 cm (6 in.) thick lead wall to filter out gamma photons. Gamma rays were maximized by thermalizing neutrons in 30.5 cm (12 in.) of water, then absorbing the thermal neutrons in a gadolinium-cadmium shield. In Phase I, 28 dogs were exposed to radiation: 12 were exposed to gamma photons at the rate of 0.69 Gy/min and 16 were exposed to neutrons at 1.2 Gy/min. In Phase II, 58 dogs in 3 groups were exposed to radiation: 19 were exposed in the gamma group at 0.75 Gy/min, 20 were exposed in the undrugged neutron group at 1.62 Gy/min, and 19 were exposed in the drug-treated neutron group. The drugged group received, 40-min pre-exposure, a combination of thiethylperazine, promethazine, and cimetidine which was previously shown to raise a 60 Co gamma ED50 bymore » 85%. The drugs were ineffective against neutron irradiation.« less