Metoclopramide protection of diazinon-induced toxicosis in chickens

First meta-analysis study of cholinesterase inhibition in experimental animals by organophosphate or carbamate insecticides under the influence of diphenhydramine

Background and Aim

Diphenhydramine is an H1-antihistamine that counteracts the toxic effects of organophosphate and carbamate insecticides that inhibit cholinesterase (ChE) activity. This meta-analysis aimed to investigate the effects of diphenhydramine on ChE inhibition induced by these insecticides in the plasma, erythrocytes, or whole brain of experimental animals.

Materials and Methods

A data search was performed on erythrocyte, plasma, and brain ChE inhibition caused by organophosphate and carbamate insecticides in experimental animals (mice, rats, and chicks) treated with the antihistamine diphenhydramine in accordance with preferred reporting items for systematic reviews and meta-analysis, which was done by the two-group random-effects model meta-analysis. The meta-analysis included 18 records extracted from six studies that, appeared from 1996 to 2022.

Results

Using the random-effects model, a two-group meta-analysis revealed that the combined effect size (ChE inhibition) was significantly more favorable in the control group than in the diphenhydramine intervention, as shown by a forest plot. The combined effect size (standardized mean difference) was 0.67, with a standard error of 0.3, a lower limit of 0.04, and an upper limit of 1.29 (p = 0.025). The heterogeneity was moderate, as I² of the combined effect size was 74%, with a significant Cochrane Q-test result (Q = 65, p < 0.0001). Subgroup analysis indicated that, with brain ChE inhibition, the heterogeneity (I²) became 5%, which was lower than ChE inhibition in plasma (84%) and erythrocytes (78%). No publication bias was identified using the funnel plot and Egger's test.

Conclusion

This meta-analysis suggests that, in addition to its documented antidotal action against ChE-inhibiting insecticides, diphenhydramine can also reduce the extent of ChE inhibition, especially in the brain, which is the main site of toxicity of these insecticides. There is a need for additional studies to assess such enzyme inhibition in different parts of the brain.

Recognition and Assessment of Antidotal Effects of Diphenhydramine against Acute Carbaryl Insecticide Poisoning in a Chick Model

Diphenhydramine antagonizes poisoning produced by cholinesterase (ChE) inhibiting insecticides. This study examines the effects of diphenhydramine against acute poisoning induced by the carbamate insecticide carbaryl in a chick model. The effects of diphenhydramine on the 24 h median Lethal Dose (LD50), and acute toxicity of carbaryl were assessed in chicks (7-15 days old). The plasma and whole brain ChE activities were measured electrometrically in vitro and in vivo. Diphenhydramine at 10mg/Kg Body wt. administered intramuscularly 15 min before carbaryl dosing increased the oral LD50 value of carbaryl (207 mg/Kg Body wt.) by 62%. Carbaryl at 250 mg/Kg Body wt. has orally produced toxidrome of cholinergic poisoning with 100% lethality in 24 h. Diphenhydramine (10mg/ Kg Body wt.) used 15 min before carbaryl (250mg/Kg Body wt., orally) was the most effective dose (vs 5 and 20mg/Kg Body wt.) in delaying carbaryl-toxicity and increasing survivals in chicks. The intramuscular median effective dose (ED50) of diphenhydramine which prevented 24 h carbaryl-death in chicks was 8.6mg/ Kg Body wt. The antidotal response to diphenhydramine was similar to that of the standard antidote atropine sulfate. Diphenhydramine at 10mg/Kg Body wt., given immediately after carbaryl (200mg/Kg Body wt.), reduced the percentages of plasma and whole brain ChE inhibitions in vivo by 12- and 13%, respectively. Carbaryl (10μmol/L) in vitro inhibited ChE activities in the plasma and brain by 53 and 77%, respectively; these inhibitions were reduced by 13- and 14%, respectively, when diphenhydramine (10μmol/L) was added to in vitro reactions. Diphenhydramine exerted antidotal action against a model of acute and lethal carbaryl intoxication in chicks.

Protective effect of metoclopramide against organophosphate-induced apoptosis in the murine skin fibroblast L929

This study was performed to evaluate the protective efficacy of metoclopramide (MCP) against the organophosphates paraoxon (POX)- and malathion (MLT)-induced apoptosis in the murine L929 skin fibroblasts. L929 cells were exposed to either POX (10 nm) or 1.0 μm MLT in the absence and presence of increased concentrations of MCP. The protective effect of MCP on these organophosphate-stimulated apoptotic events was evaluated by flow cytometry analysis after staining with annexin-V/propidium iodide, processing and activation of the executioner caspase-3, cleavage of the poly-ADP ribose polymerase, fragmentation of the nucleosomal DNA and disruption of the mitochondrial membrane potential (Δψ). Our results showed that increased doses of MCP alone (≥10 μm) did not induce apoptosis or activation of caspase-3. Pretreatment of the cells with MCP attenuated all the apoptotic events triggered by the organophosphate compounds in a dose-dependent manner reaching ~70-80% protection when they were preincubated at 1 and 5 μm of the drug before the addition of POX and MLT, respectively. Interestingly, MCP did not offer a significant protective effect against the cytotoxicity of tumor necrosis factor-α, cisplatinum, etoposide or paclitaxel, which stimulate apoptosis by various mechanisms, suggesting that the anti-apoptotic effect of the drug is specific to organophosphates. The strong and specific anti-apoptotic activity of subclinical doses of MCP against the cytotoxicity of organophosphate compounds suggests its potential clinical application in treating their poisoning.

Acute toxicity of veterinary and agricultural formulations of organophosphates dichlorvos and diazinon in chicks

Formulation components of organophosphate insecticidal preparations might affect their toxic action in animals. The objective of this study was to examine and compare the acute toxicity and cholinesterase inhibition in seven to 14-day-old chicks dosed orally with dichlorvos and diazinon in standard veterinary and agricultural formulations. The acute (24 h) oral median lethal doses (LD50) of the formulations were determined using the up-and-down method. Respective LD50 of dichlorvos of the veterinary and agricultural formulations in chicks were 11.1 mg kg(-1) and 6.51 mg kg(-1) and those of diazinon 6.4 mg kg(-1) and 6.7 mg kg(-1). Plasma and brain cholinesterase activities were measured by electrometry after in vivo and in vitro exposure to organophosphates. The chicks showed signs of cholinergic toxicosis within one hour of dosing. Dichlorvos (8 mg kg(-1)) and diazinon (4 mg kg(-1)) in the veterinary and agricultural formulation significantly reduced both plasma and brain cholinesterase activities in the chicks. The veterinary formulation of dichlorvos reduced plasma ChE by 60% and agricultural by 40% and brain ChE by 93% and 87%, respectively. In contrast, ChE inhibition by diazinon in the agricultural formulation of diazinon was stronger than by the veterinary formulation; 72% vs. 64% in plasma and 97% vs. 80% in the brain, respectively. The highest in vitro inhibitions were observed with dichlorvos in the agricultural formulation (50%) in the brain samples and with diazinon in the agricultural formulation (52%) in the plasma samples. While they exist, differences between formulations cannot be taken as a rule and further investigations should inventory the toxicity of standard veterinary and agricultural organophosphate formulations in addition to the known data for pure forms.

Acute Toxicity and Cholinesterase Inhibition in Chicks Dosed Orally with Organophosphate Insecticides

Acute toxic effects of three commonly used insecticidal preparations of the organophosphates chlorpyrifos, diazinon, and dichlorvos were examined in mixed breed broiler chicks, and cholinesterase activity in plasma and brain were measured. The acute (24 h) oral median lethal doses (LD50) of chlorpyrifos, diazinon, and dichlorvos were 10.79 mg kg-1, 6.32 mg kg-1, and 6.30 mg kg-1, respectively, as determined by the up-and-down method in chicks. Signs of cholinergic toxicosis in the chicks appeared within two hours after dosing, and they included salivation, lacrimation, gasping, frequent defecation, drooping of wings, tremors, convulsions, and recumbency before death. Halving the oral LD50 of chlorpyrifos (5 mg kg-1), diazinon (3 mg kg-1), and dichlorvos (3 mg kg-1) caused immobility and wing drooping, but not the clinical signs of cholinergic toxicity. However, at full LD50 doses of these insecticides, chicks showed clinical signs of cholinergic toxicity similar to those seen in the LD50 experiments. Two out of six chicks died within two hours after treatment with LD50 doses of chlorpyrifos and dichlorvos, whereas LD50 dosing with diazinon caused death in three out of six chicks. Compared to control values, the insecticides reduced plasma and whole brain cholinesterase activities by 29 % to 84 % and 18 % to 77 %, respectively, depending on the dose. The decrease in plasma cholinesterase correlated well (r = 0.82) with that of the brain. These data suggest that organophosphate insecticides administered orally at LD50 doses induce clinical signs of cholinergic poisoning and concurrently reduce brain and plasma cholinesterase activities in chicks.