title: Intravenous cobinamide versus hydroxocobalamin for acute treatment of severe cyanide poisoning in a swine (Sus scrofa) model.
abstract: OBJECTIVE
  Hydroxocobalamin is a Food and Drug Administration-approved antidote for cyanide poisoning. Cobinamide is a potential antidote that contains 2 cyanide-binding sites. To our knowledge, no study has directly compared hydroxocobalamin with cobinamide in a severe, cyanide-toxic large-animal model. Our objective is to compare the time to return of spontaneous breathing in swine with acute cyanide-induced apnea treated with intravenous hydroxocobalamin, intravenous cobinamide, or saline solution (control).
  
  
  METHODS
  Thirty-three swine (45 to 55 kg) were intubated, anesthetized, and instrumented (continuous mean arterial pressure and cardiac output monitoring). Anesthesia was adjusted to allow spontaneous breathing with FiO2 of 21% during the experiment. Cyanide was continuously infused intravenously until apnea occurred and lasted for 1 minute (time zero). Animals were then randomly assigned to receive intravenous hydroxocobalamin (65 mg/kg), cobinamide (12.5 mg/kg), or saline solution and monitored for 60 minutes. A sample size of 11 animals per group was selected according to obtaining a power of 80%, an α of .05, and an SD of 0.17 in mean time to detect a 20% difference in time to spontaneous breathing. We assessed differences in time to death among groups, using Kaplan-Meier estimation methods, and compared serum lactate, blood pH, cardiac output, mean arterial pressure, respiratory rate, and minute ventilation time curves with repeated-measures ANOVA.
  
  
  RESULTS
  Baseline weights and vital signs were similar among groups. The time to apnea and cyanide dose required to achieve apnea were similar. At time zero, mean cyanide blood and lactate concentrations and reduction in mean arterial pressure from baseline were similar. In the saline solution group, 2 of 11 animals survived compared with 10 of 11 in the hydroxocobalamin and cobinamide groups (P<.001 between the 2 treated groups and the saline solution group). Time to return of spontaneous breathing after antidote was similar between hydroxocobalamin and cobinamide (1 minute 48 seconds versus 1 minute 49 seconds, respectively). Blood cyanide concentrations became undetectable at the end of the study in both antidote-treated groups, and no statistically significant differences were detected between the 2 groups for mean arterial pressure, cardiac output, respiratory rate, lactate, or pH.
  
  
  CONCLUSIONS
  Both hydroxocobalamin and cobinamide rescued severely cyanide-poisoned swine from apnea in the absence of assisted ventilation. The dose of cobinamide was one fifth that of hydroxocobalamin.
authors.affiliation: Medical Toxicology, San Antonio Military Medical Center, San Antonio, TX. Electronic address: vikbebarta@yahoo.com.
authors.forename: Vikhyat S
authors.initials: VS
authors.lastname: Bebarta
authors.affiliation: David Geffen School of Medicine at UCLA, Harbor-UCLA Medical Center, Torrance, CA.
authors.forename: David A
authors.initials: DA
authors.lastname: Tanen
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, San Antonio, TX.
authors.forename: Susan
authors.initials: S
authors.lastname: Boudreau
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, San Antonio, TX.
authors.forename: Maria
authors.initials: M
authors.lastname: Castaneda
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, San Antonio, TX.
authors.forename: Lee A
authors.initials: LA
authors.lastname: Zarzabal
authors.affiliation: Department of Emergency Medicine, San Antonio Military Medical Center, San Antonio, TX.
authors.forename: Toni
authors.initials: T
authors.lastname: Vargas
authors.affiliation: University of California, San Diego, San Diego, CA.
authors.forename: Gerry R
authors.initials: GR
authors.lastname: Boss
mesh_terms: D000818:Animals; D000931:Antidotes / Q000627:therapeutic use*; D001049:Apnea / Q000139:chemically induced / Q000188:drug therapy*; D003038:Cobamides / Q000627:therapeutic use*; D003486:Cyanides / Q000506:poisoning*; D004195:Disease Models, Animal; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006879:Hydroxocobalamin / Q000627:therapeutic use*; D007262:Infusions, Intravenous; D011041:Poisoning / Q000188:drug therapy / Q000503:physiopathology; D011897:Random Allocation; D013552:Swine
chemical_list: D000931:Antidotes; D003038:Cobamides; D003486:Cyanides; C017142:cobinamide; D006879:Hydroxocobalamin
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