Cyclophosphamide treatment of paraquat poisoning

Rapamycin reduces mortality in acute-stage paraquat-induced toxicity in zebrafish

INTRODUCTION

Paraquat (PQ) intoxication is frequently associated with a high mortality rate. No specific treatment has been shown to reduce mortality in victims within the first 72 hours. We investigated the protective effects of rapamycin (Rapa) against PQ-induced toxicity in a zebrafish model.

METHODS

To determine the maximum nonlethal concentration (MNLC) and lethal concentration 50 (LC50) of Rapa, zebrafish were treated at 2-5 days post fertilisation (dpf) and their mortality was recorded every 24 hours. At 5 dpf, the zebrafish were treated with PQ 100 µg/mL or PQ+Rapa (MNLC, 1/3 MNLC or 1/9 MNLC) for 72 hours, and the rate of survival was recorded every 24 hours. Reverse transcription-polymerase chain reaction was used to test the signalling pathway of mTOR (mammalian target of rapamycin).

RESULTS

MNLC and LC50 of Rapa were determined to be 6.7 µg/mL and 28.9 µg/mL, respectively. At 48 hours, the PQ+Rapa groups had much lower mortality than the PQ group. The rates of survival of the PQ+Rapa groups were 43.33% (MNLC), 53.89% (1/3 MNLC) and 44.45% (1/9 MLNC), as compared to 19.45% in the PQ group, with the 1/3 MNLC group showing the highest rate of survival (p < 0.001). atg1 was slightly activated in the PQ group. In the PQ+Rapa groups, the expression of atg1 was markedly increased, suggesting strengthening of the autophagy process.

CONCLUSION

Rapa can increase the rate of survival of PQ-intoxicated zebrafish by inhibiting mTOR complex 1 and activating autophagy. Rapa could be an alternative first-line drug in the treatment of PQ poisoning.

Delayed death following paraquat poisoning: three case reports and a literature review

Paraquat (PQ) poisoning is principally reported in developing countries. However, most fatalities occur elsewhere due to the induction of multi-organ failure. PQ poisoning can hardly be managed by clinical practice, and no specific antidote has come into existence yet. Here three cases, including 17-, 20-, and 23-year-old men, who were poisoned with PQ, have been reported. Furthermore, the literature regarding biological mechanisms, clinical manifestation, and treatment of PQ-induced toxicity was reviewed. Patients who, either intentionally or accidentally, ingested PQ earlier were initially found to be stable at the emergency department (ED). Therefore, they were discharged from the hospital under a follow-up. However, after several days, the patients were referred to the hospital for the second time and despite cardiovascular resuscitation (CPR) efforts, they suddenly expired. The delayed death following exposure to PQ was reported for inducing gradual progressive pulmonary fibrosis, metabolic acidosis, neurotoxicity, renal failure, and liver injury in poisoned patients. Therefore, PQ-intoxicated patients should be supervised for up to several weeks, and kept in the hospital for a longer period of time. Clinical manifestations and laboratory findings are beneficial markers that act as useful predictors of PQ poisoning.

Experimental study of sucralfate intervention for paraquat poisoning in rats

OBJECTIVE

This study explored the effects of sucralfate intervention as a novel treatment for paraquat (PQ) poisoning in Sprague-Dawley (SD) rats.

METHODS

After PQ poisoning, the SD rats were randomly divided into the PQ control group (treated with normal saline), the sodium bicarbonate (SB) treatment group, and the sucralfate (LTL) treatment group. Then, the rats were administered normal saline, sodium bicarbonate solution, or sucralfate suspension as an intervention by gastric lavage. At 1, 3, 6, and 10days after poisoning, the left lungs of some rats were removed to determine the lung wet/dry (W/D) weight ratio. Additionally, the serum cytokine levels were measured, and the lung and kidney tissues were pathologically examined.

RESULTS

After treatment, the signs and symptoms of the rats were improved, the mortality rate was reduced, the W/D weight ratio of the lung was lower, the cytokine levels [transforming growth factor (TGF)-β1, interleukin (IL)-10, and tumor necrosis factor (TNF)-α] were decreased, and the pathological injuries of the lungs and kidneys were improved. Moreover, sucralfate was significantly more effective than the control (normal saline) group and the SB treatment group.

CONCLUSION

The results showed that early gastrointestinal lavage with sucralfate effectively reduced the inflammatory response and lung and kidney injuries and improved the survival of the SD rats.

To Explore the Characteristics of Fatality in Children Poisoned by Paraquat – with Analysis of 146 Cases

Purpose

The incidence of paraquat (PQ) poisoning in China is increasing, so it is important to identify the characteristics of fatalities in children with acute PQ poisoning in order to prevent and treat future cases.

Methods

A prospective study that enrolled 146 children with PQ poisoning was performed. A novel evaluation system called the score of lethal factors for PQ poisoning (SLFPP) was established, including 1 contributing factor and 4 weakening factors. Comparisons with the Pediatric Logistic Organ Dysfunction (PELOD) score, the Poisoning Severity Score (PSS) in admission and the SLFPP were made to determine their values for prognosis.

Results

Younger patients (71/146, <10 years) had accidental exposure to PQ (64/71, 90.14%), whereas older patients (75/146, ≥10 years) had ingested PQ intentionally (46/75, 61.33%) (p<0.01); 21/146 (14.38%) died of PQ poisoning. Of these 21 children, 20 committed suicide with ages ≥10 years. Significant differences (p<0.01) were found between nonsurvivors and survivors with regard to the Pediatric Logistic Organ Dysfunction (PELOD) scores (19.76 ± 18.44 vs. 4.17 ± 5.98), PSS in admission (2.48 ± 0.60 vs. 1.43 ± 0.59), the SLFPP (10.40 ± 1.07 vs. 3.60 ± 1.89). In PELOD score and PSS in admission, there were relative large overlaps in scores between nonsurvivors and survivors. But for SLFPP, there were smaller overlaps.

Conclusions

Deliberate ingestion of PQ to commit suicide occurred mainly in older children (≥10 years), while accidental exposure to PQ occurred mainly in younger children (<10 years). Owing to small overlaps, the SLFPP may exceed PELOD and PSS in predicting the prognosis of PQ poisoning, but the SLFPP scores still require further clinical validation.

The effect of amifostine, a cytoprotective agent, on paraquat toxicity in mice

BACKGROUND

Paraquat (PQ) is a highly poisonous herbicide with a variety of toxic effects, most notably pulmonary fibrosis. In alveolar epithelial cells, it is converted to a PQ radical and subsequently generates other reactive species resulting in lipid peroxidation and cell destruction. Amifostine is a thiophosphate prodrug approved by the FDA for the prevention of toxicities associated with cisplatin and therapeutic radiation. When amifostine is converted to an active metabolite (WR-1065), it functions as an oxygen and DNA radical scavenger that has been shown to protect against lipoperoxidation. The aim of this study was to determine whether amifostine improves survival or lung injury resulting from PQ toxicity.

METHODS

Swiss mice (n = 23 per group) were given an approximate LD75 dose of PQ intraperitoneal (60 mg/kg). Thirty minutes prior to PQ injection, group 1 was pretreated with 200 mg/kg of amifostine subcutaneously (s.c.). Subsequent doses of amifostine at 75 mg/kg were administered 4 hours after PQ injection, and injections continued every 8 hours for a total of 6 doses (cumulative dose: 575 mg/kg). Four hours after PQ injection, group 2 received 200 mg/kg of amifostine subcutaneously. Subsequent doses of amifostine at 75 mg/kg were administered every 8 hours (cumulative dose: 575 mg/kg). Four hours after PQ injection, group 3 received 100 mg/kg of amifostine subcutaneously. Subsequent doses of amifostine at 30 mg/kg were administered every 8 hours (cumulative dose: 250 mg/kg). Group 4 received equivolume injections of sterile 0.9% saline s.c. at the same time intervals. We removed lungs from all mice for histologic analysis and injury scoring.

RESULTS

The number of surviving mice in groups 1, 2, 3, and 4 were 17, 18, 17, and 17 respectively. The Kaplan-Meier with log rank analysis showed no differences in survival. Lung injury scores did not differ between treatment groups and the control group for either dead or surviving mice.

CONCLUSION

Amifostine does not appear to improve survival or lung injury due to PQ toxicity at the doses administered.

Prospects for treatment of paraquat-induced lung fibrosis with immunosuppressive drugs and the need for better prediction of outcome: a systematic review

BACKGROUND

Acute paraquat self-poisoning is a significant problem in parts of Asia, the Pacific and the Caribbean. Ingestion of large amounts of paraquat results in rapid death, but smaller doses often cause a delayed lung fibrosis that is usually fatal. Anti-neutrophil ('immunosuppressive') treatment has been recommended to prevent lung fibrosis, but there is no consensus on efficacy.

AIM

To review the evidence for the use of immunosuppression in paraquat poisoning, and to identify validated prognostic systems that would allow the use of data from historical control studies and the future identification of patients who might benefit from immunosuppression.

DESIGN

Systematic review.

METHODS

We searched PubMed, Embase and Cochrane databases for 'paraquat' together with 'poisoning' or 'overdose'. We cross-checked references and contacted experts, and searched on [www.google.com] and [www.yahoo.com] using 'paraquat', 'cyclophosphamide', 'methylprednisolone' and 'prognosis'.

RESULTS

We found ten clinical studies of immunosuppression in paraquat poisoning. One was a randomized controlled trial (RCT). Seven used historical controls only; the other two were small (n = 1 and n = 4). Mortality in controls and patients varied markedly between studies. Three of the seven non-RCT controlled studies measured plasma paraquat; analysis using Proudfoot's or Hart's nomograms did not suggest that immunosuppression increased survival in these studies. Of 16 prognostic systems for paraquat poisoning, none has been independently validated in a large cohort.

DISCUSSION

The authors of the RCT have performed valuable and difficult research, but their results are hypothesis-forming rather than conclusive; elsewhere, the use of historical controls is problematic. In the absence of a validated prognostic marker, a large RCT of immunosuppression using death as the primary outcome is required. This RCT should also prospectively test and validate the available prognostic methods, so that future patients can be selected for this and other therapies on admission.

[Paraquat poisoning. A study of 29 cases and evaluation of the effectiveness of the "Caribbean scheme"]

BACKGROUND

To study clinical aspects of the oral paraquat intoxication and to assess the effectiveness of both the charcoal haemoperfusion and the so-called "Caribbean scheme" (cyclophosphamide, dexamethasone, furosemide and vitamins B and C) to reduce its mortality.

PATIENTS AND METHOD

Retrospective study of 29 consecutive cases admitted to our intensive care unit in 17 years.

RESULTS

a) Twenty five men and four women ingested 20% paraquat solution, either accidentally (4 subjects) or deliberately (25 subjects). The suicidal purpose was particularly strong among men aged 50-66 years. Most of patients had vomits and diarrhoea. All patients developed oral and pharyngeal caustic lesions. Hypokalaemia was detected on admission in 9 patients. Increased levels of serum aminotransferases, bilirubin, amylase or creatinkinase were detected in some patients. Twenty two patients developed acute renal failure and 18 patients respiratory failure. Twenty patients died (ten in the first 48 hours and ten between days 3 and 30); b) charcoal haemoperfusion was performed on 16 patients; 4 of the 16 treated patients survived, versus 5 of the 13 non treated (p = NS), and c) the "Caribbean scheme" was applied on 18 patients. All but one of the 11 subjects who ingested >= 45 ml (treated with the "Caribbean scheme" or not) died. Among those who ingested 45 ml, 8 of the 12 treated patients survived, versus none of the 6 non treated ones (p < 0.05).

CONCLUSIONS

Charcoal haemoperfusion did not reduce mortality of paraquat. The "Caribbean scheme" was associated with a lesser mortality in the subjects who ingested 45 ml of 20% paraquat solution.

[Massive paraquat poisoning. Favorable course after treatment with n-acetylcysteine and early hemodialysis]

Case report of a 30-year-old patient, admitted one hour after an intentional ingestion of paraquat (60 g). The initial treatment included gastric washing, parenteral n-acetylcysteine and forced diuresis. Considering the severity of the intoxication, conventional haemodialysis was started four hours after the ingestion. Plasma concentrations of paraquat, in the lethal range at admission, decreased rapidly and significantly after haemodialysis. This case raises the question of the part played by n-acetylcysteine and haemodialysis respectively in a favourable outcome. As the determination of paraquat blood concentrations requires some delay, these data are of no help for therapeutic decisions. Therefore, in cases of massive poisoning or uncertainty of the ingested dose, a technique of blood purification in indicated. Charcoal haemoperfusion is the most efficient, however conventional haemodialysis, which is more widespread, should be considered if the former is not available.