Pathophysiology and diagnosis

The acute human oral toxic dose of Basta® that causes delayed central nervous system disorders has been estimated at 1.6 to 1.8 ml/kg, i.e. 320 to 360 mg/kg of glufosinate ammonium (Koyamaefal 199.5 a). In reported cases, 85 per cent of patients who ingested 100 ml or more of Basta®, and 30 per cent of patients who ingested less than 100 ml, developed respiratory failure requiring mandatory ventilation.

Glufosinate is a potent inhibitor of glutamine synthetase which catalyzes the formation of glutamine from glutamate and ammonia. However, the pathophysiology of human poisoning has not been clarified. The surfactant component is suspected to cause gastrointestinal irritation and circulatory failure.

Immediately after ingestion, patients complain of nausea and vomiting, but these symptoms subside within a few hours. However, 8 to 38 h after ingestion, patients develop disturbance of consciousness and respiratory arrest. Other delayed signs are agitation, tremor, seizures, nystagmus, ataxic gait, pyrexia, etc. Retrograde partial amnesia is also recognized on recovery. In severe cases, patients have died of refractory circulatory failure which is believed to be due to the surfactant component.

The diagnosis can be obtained by analyzing the patient's urine using paper chromatography.

The serum glufosinate level related to time from ingestion in several reported cases is shown in Fig.: 1... Central nervous system signs develop after the serum glufosinate level decreases, and persist for several days. It may be possible to predict the development of delayed signs from the serum glufosinate level.

Fig. 1 Changes in serum glufosinate level in 20 reported cases of acute oral Basta® poisoning: o level in patients with severe poisoning ( n = 14) who developed coma, respiratory arrest, or generalized convulsion; • level in patients with non-severe poisoning ( n = 6) who did not develop these signs. Serial data from the same patient are connected by solid lines. The dotted line connecting 70 ppm at 2 h and 5 ppm at 8 h appears to discriminate between severe and non-severe patients. (Reproduced with permission from Kgyama.. § (1997).)

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