Estimation of Monocrotophos renal elimination half-life in humans.

INTRODUCTION: Monocrotophos, implicated in about 1/4th of organophosphate poisonings in our centre, is associated with the highest mortality (24%). Yet data on its pharmacokinetics in humans is limited. We estimated the renal elimination half-life of monocrotophos. PATIENTS AND METHODS: Consecutive patients presenting with monocrotophos overdose over a 2-month period who had normal renal function were recruited. Monocrotophos in plasma and urine were quantitated by high-performance liquid chromatography. Urine was obtained from catheterised samples at 0-2, 2-4, 4-6, 6-8, 8-12 and 12-24 h. Plasma specimens were collected at the time of admission, and at the midpoint of the urine sample collections at 1, 3, 5, 7, 10, 15 and 21 h. Renal elimination half-life was calculated from the cumulative amount excreted in the urine. RESULTS: The cohort of 5 male patients, aged 35.8 ± 2.94 years, presented with typical organophosphate (cholinergic) toxidrome following intentional monocrotophos overdose. All patients required mechanical ventilation; one patient died. Plasma data was available from 5 patients and urine data from 3 patients. The median renal elimination half-life was 3.3 (range: 1.9-5.0 h). Plasma monocrotophos values, as natural log, fell in a linear fashion up to around 10 h after admission. After the 10-hour period, there was a secondary rise in values in all the 3 patients in whom sampling was continued after 10 h. CONCLUSION: A renal elimination half-life of 3.3 h for monocrotophos is consistent with a water-soluble compound which is rapidly cleared from the plasma. The secondary rise in plasma monocrotophos values suggests possible re-distribution. Determining the elimination profile of this compound will help develop better strategies for treatment.

Detection of DNA damage in mouse peripheral blood leukocytes by the comet assay after oral administration of monocrotophos.

The objective of this study was to determine if single/double strand DNA breaks could be induced by monocrotophos (organophosphorus pesticide) in mice in vivo using the comet assay. Mice were dosed orally with 0.046, 0.093, 0.186, 0.373 and 0.746 mg/kg body weight of monocrotophos, and the assay was performed on whole blood after 24, 48 and 72 h. A significant increase in mean comet tail length indicating DNA damage was observed at 24 and 48 h post-treatment with monocrotophos when compared to controls. A decrease in the mean tail length was observed at 72 h post-treatment indicating repair of the damaged DNA. The mean tail length showed a dose-related increase and time dependent decrease. The study reveals that comet assay is a sensitive and rapid method to detect genotoxicity of monocrotophos.

[The profiles of free organophosphorus poisons in the bile of rabbits poisoned with different organophosphates].

OBJECTIVE: To study the process and significance of the distribution of free organophosphorus poisons (FOPs) in the blood and bile of rabbits poisoned with organophosphates. METHODS: Seventy two livid blue rabbits, male, 2 - 2.5 kg in weight, were divided into 3 groups: trichlorfon (556.0 mg/kg), monocrotophos (11.12 mg/kg) and methyl parathion (37.05 mg/kg). Each group consisted of 24 rabbits. All organophosphates were administered by subcutaneous route. Blood and bile were collected at time intervals of 1, 6, 24, 96 hours after administration. Blood cells and plasma were separated. Acetylcholinesterase (AChE) activity was measured with dithiobisnitrobenzoic acid (DTNB) enzyme kinetic method. The levels of FOPs in plasma and bile were determined with enzyme inhibited method. RESULTS: From 1 h to 96 h after administration negative correlation was found between time and FOP concentration in plasma (trichlorfon, r = -0.74, P < 0.01; monocrotophos, r = -0.55, P < 0.01; methyl parathion, r = -0.69, P < 0.01), and it was also found in bile between time and FOP concentration of trichlorfon (r = -0.97, P < 0.01) and monocrotophos (r = -0.71, P < 0.01). There is no linear correlation between time and concentration of methyl parathion in bile (r = -0.14, P > 0.05). When FOPs in plasma were not detectable at 96 h after administration, high levels of FOPs could still be detected in bile [trichlorfon (300.3 +/- 174.44) IU/L; monocrotophos (362.8 +/- 136.62) IU/L; methyl parathion (101.0 +/- 75.85) IU/L]. CONCLUSION: The bile is the most important store for FOPs in animal. FOPs can exist in bile over 96 h. The process of poisoning is a changing process of absorption, distribution and redistribution and it is different owing to various physical and chemical properties of organophosphates.