Intramuscular ophthalmic homatropine vs. atropine to prevent lethality in rates with dichlorvos poisoning.
BACKGROUND
Most hospitals lack a sufficient supply of atropine to treat, simultaneously, patients poisoned with multiple organophosphorous compound (OC) or nerve agent. The presence of a ubiquitous alternate antidote would prove useful if mass poisoning occurred. Our objective was to evaluate the effect of ophthalmic homatropine (Isopto Homatropine 5%) on survivability in a rat model of significant, acute OC poisoning.


METHODS
Sprague-Dawley rats were randomized to one of five pre-treatment groups (N = 10 per group). Prior to experimentation, animals were pre-treated with intramuscular (IM) injections of either atropine 5 mg/kg, atropine 10 mg/kg, homatropine 10 mg/kg, or homatropine 20 mg/kg. The control group received 0.3 mL normal saline IM. Five minutes later, 25 mg/kg of dichlorvos was subcutaneously administered. Mortality rates were compared using Fisher's Exact test. Kaplan-Meier survival curves with Logrank analysis was also performed. If alive at 120 minutes, survival was assumed, and the study was terminated.


RESULTS
All rats pre-treated with normal saline, atropine 5 mg/kg, and homatropine 10 mg/kg died. Survival in the homatropine (20 mg/kg) and atropine (10 mg/kg) groups was 30% and 40% respectively. Times to death ranged between 4 and 12 minutes. Overall comparison of time to death revealed a statistically significant improvement for groups pre-treated with homatropine (20 mg/kg) and atropine (10 mg/kg).


CONCLUSIONS
Pre-treatment with homatropine (20 mg/kg) was comparable with atropine (10 mg/kg) in preventing lethality in this rat model of acute OC poisoning.
Bryant
Sean M
SM
Cook County-Stroger Hospital, Department of Emergency Medicine, Chicago, IL, USA. sbryant@ccbh.org
Wills
Brandon K
BK
Rhee
James W
JW
Aks
Steven E
SE
Maloney
Gerald
G
D000208:Acute Disease; D000818:Animals; D000931:Antidotes / Q000008:administration & dosage*; D001285:Atropine / Q000008:administration & dosage*; D002800:Cholinesterase Inhibitors / Q000506:poisoning; D004006:Dichlorvos / Q000506:poisoning; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D007273:Injections, Intramuscular; D008297:Male; D009883:Ophthalmic Solutions / Q000008:administration & dosage*; D011041:Poisoning / Q000209:etiology / Q000401:mortality / Q000517:prevention & control; D051381:Rats; D017207:Rats, Sprague-Dawley; D013997:Time Factors; D014326:Tropanes / Q000008:administration & dosage*
D000931:Antidotes; D002800:Cholinesterase Inhibitors; D009883:Ophthalmic Solutions; D014326:Tropanes; D001285:Atropine; D004006:Dichlorvos; C100236:homatropine