Medical management of paraquat ingestion

Abstract

Poisoning by paraquat herbicide is a major medical problem in parts of Asia while sporadic cases occur elsewhere. The very high case fatality of paraquat is due to inherent toxicity and lack of effective treatments. We conducted a systematic search for human studies that report toxicokinetics, mechanisms, clinical features, prognosis and treatment. Paraquat is rapidly but incompletely absorbed and then largely eliminated unchanged in urine within 12-24 h. Clinical features are largely due to intracellular effects. Paraquat generates reactive oxygen species which cause cellular damage via lipid peroxidation, activation of NF-kB, mitochondrial damage and apoptosis in many organs. Kinetics of distribution into these target tissues can be described by a two-compartment model. Paraquat is actively taken up against a concentration gradient into lung tissue leading to pneumonitis and lung fibrosis. Paraquat also causes renal and liver injury. Plasma paraquat concentrations, urine and plasma dithionite tests and clinical features provide a good guide to prognosis. Activated charcoal and Fuller's earth are routinely given to minimize further absorption. Gastric lavage should not be performed. Elimination methods such as haemodialysis and haemoperfusion are unlikely to change the clinical course. Immunosuppression with dexamethasone, cyclophosphamide and methylprednisolone is widely practised, but evidence for efficacy is very weak. Antioxidants such as acetylcysteine and salicylate might be beneficial through free radical scavenging, anti-inflammatory and NF-kB inhibitory actions. However, there are no published human trials. The case fatality is very high in all centres despite large variations in treatment.

Successful treatment of patients with paraquat intoxication: three case reports and review of the literature

“…et al (2011) reported that repeated pulses of methylprednisolone and cyclophosphamide (CTX) may result in a lower mortality rate in patients with severe PQ poisoning. However, Gawarammana and Buckley (2011) reported that the case fatality is very high in all centers despite large variations in treatments containing HP, immunosuppression therapy, and antioxidants.…”

Detection of the desiccant and plant growth regulator chlormequat in honeybees and comb pollen

“…Another quat that we detected in some of the samples of the dying bees was paraquat, which is important because this pesticide has been banned in the EU since 2007 (Court of Justice 2007, http://eur-lex.europa.eu/legal-content/EN/ALL/?uri=CELEX:62004TJ0229). However, while paraquat is considered extremely hazardous to humans (Gawarammana and Buckley 2011), in bees it is considered practically non-toxic or only slightly toxic (Tables S4-S7 in ESM).…”

Paraquat tongue

“…Hemoperfusion and hemodialysis is considered in patients with renal failure and pulmonary edema [1,2]. The presence of paraquat tongue should warrant a clinician to carefully look for GI perforation, mediastinitis, pneumothorax, and pneumomediastinum (Fig.…”