Abstract
In vitro inhibition of human plasma and erythrocyte cholinesterase activities by the
strong cholinesterase inhibitor chlorpyriphos (organophosphate) and the weak
cholinesterase inhibitors (donepezil, metoclopramide, and diphenhydramine) in
different concentrations was evaluated. The protective ability of each one of the weak
cholinesterase inhibitors alone and with a combination of two of them against the
inhibitory action of chlorpyriphos was also detected. The results showed different
patterns of inhibition depending on the inhibitor and its concentration when used
alone or within a combination. When testing the protective ability, the results differed
for each one of the inhibitors and for the combinations, depending on its own ability
to bind the cholinesterase. Donepezil showed no ability to protect the enzyme against
chlorpyriphos, but caused further increase in the inhibition when used alone or in
combination. Diphenhydramine could have affinity to bind the enzyme more than
metoclopramide and donepezil when used in combination against chlorpyriphos
toxicity, and metoclopramide had higher affinity to inhibit erythrocyte cholinesterase
in combination more than diphenhydramine and donepezil . The use of weak
cholinesterase inhibitors alone or in combination may reduce the toxicity of
organophosphates depending on the inhibitor used , but still not to a significant extent.
