Pretreatment for acute exposure to diisopropylfluorophosphate: in vivo efficacy of various acetylcholinesterase inhibitors.
Prophylactic administration of reversible acetylcholinesterase (AChE) inhibitors before exposure to organophosphorus compounds (OPCs) can reduce OPC-induced mortality. Pyridostigmine is the only FDA-approved substance for such use. The AChE-inhibitory activity of known AChE inhibitors was quantified in vitro and their in vivo mortality-reducing efficacy was compared, when given prophylactically before the exposure to the OPC diisopropylfluorophosphate (DFP). The IC50 was measured in vitro for the known AChE inhibitors pyridostigmine, physostigmine, ranitidine, tiapride, tacrine, 7-methoxytacrine, amiloride, metoclopramide, methylene blue and the experimental oxime K-27. Their in vivo efficacy, when given as pretreatment, to protect rats from DFP-induced mortality was quantified by determining the relative risk of death (RR) by Cox analysis, with RR = 1 for animals given only DFP, but no pretreatment. Physostigmine was the strongest in vitro AChE-inhibitor (IC50 = 0.012 µ m), followed by 7-methoxytacrine, tacrine, pyridostigmine and methylene blue. Ranitidine (IC50 = 2.5 µ m), metoclopramide and amiloride were in the mid-range. Tiapride (IC50 = 256 µ m) and K-27 (IC50 = 414 µ m) only weakly inhibited RBC AChE activity. Best in vivo protection from DFP-induced mortality was achieved when physostigmine (RR = 0.02) or tacrine (RR = 0.05) was given before DFP exposure, which was significantly superior to the pretreatment with all other tested compounds, except K-27 (RR = 0.18). The mortality-reducing effect of pyridostigmine, ranitidine and 7-methoxytacrine was inferior, but still significant. Tiapride, methylene blue, metoclopramide and amiloride did not significantly improve DFP-induced mortality. K-27 may be a more efficacious alternative to pyridostigmine, when passage into the brain precludes administration of physostigmine or tacrine.
Lorke
Dietrich E
DE
Department of Anatomy, FMHS, UAE University, Al Ain, UAE; Department of Cellular Biology and Pharmacology, Florida International University, Miami, FL, USA.
Hasan
Mohamed Y
MY
Nurulain
Syed M
SM
Shafiullah
Mohamed
M
Kuča
Kamil
K
Petroianu
Georg A
GA
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002800:Cholinesterase Inhibitors / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004912:Erythrocytes / Q000201:enzymology; D005260:Female; D006801:Humans; D020128:Inhibitory Concentration 50; D007531:Isoflurophate / Q000633:toxicity*; D008297:Male; D008751:Methylene Blue / Q000494:pharmacology; D008787:Metoclopramide / Q000494:pharmacology; D010091:Oximes / Q000494:pharmacology; D010830:Physostigmine / Q000494:pharmacology; D016016:Proportional Hazards Models; D011726:Pyridinium Compounds / Q000494:pharmacology; D011729:Pyridostigmine Bromide / Q000494:pharmacology; D011899:Ranitidine / Q000494:pharmacology; D051381:Rats; D013619:Tacrine / Q000031:analogs & derivatives / Q000494:pharmacology; D063325:Tiapride Hydrochloride / Q000494:pharmacology
C513728:4-(aminocarbonyl)-1-(3-(4-((E)-(hydroxyimino)methyl)pyridinium-1-yl)propyl)pyridinium dibromide; D002800:Cholinesterase Inhibitors; D010091:Oximes; D011726:Pyridinium Compounds; D007531:Isoflurophate; D013619:Tacrine; D063325:Tiapride Hydrochloride; C016222:7-methoxytacrine; D000584:Amiloride; D011899:Ranitidine; D010830:Physostigmine; D011729:Pyridostigmine Bromide; D008787:Metoclopramide; D008751:Methylene Blue