The pharmacokinetics of chlorinated phenoxy acid herbicides: a literature review.

The chlorinated phenoxy acid herbicides (CPAHs) appear to have similar pharmacokinetics. They are rapidly and almost completely absorbed from an oral dose. They distribute to other tissues and are highly protein-bound in the plasma. The CPAHs are rapidly eliminated unchanged in the urine by an active process in the kidneys. Increasing doses apparently influence absorption, metabolism, distribution and elimination of the CPAHs so that biological effects are increased. Combinations of CPAHs are likely to result in additive or potentiated biological effects. Data suggest that CPAH toxicosis may be alleviated by treatment with fluids and bicarbonate to increase urinary pH and volume, thereby increasing excretion.

2,4-D toxicosis. I: A pilot study of 2,4-dichlorophenoxyacetic acid- and dicamba-induced myotonia in experimental dogs.

English Pointer dogs dosed po with encapsulated 2,4-dichlorophenoxyacetic acid (2,4-D) or 2-methoxy-3,6-dichlorobenzoic acid (dicamba) developed varying degrees of myotonia. Dogs given 175 or 220 mg of 2,4-D/kg body weight rapidly developed clinical and electromyographic (EMG) manifestations consistent with a diagnosis of myotonia or pseudomyotonia. Dogs given 2,4-D at 86.7, 43.7 or 8.8 mg/kg body weight developed subclinical manifestations of myotonia detectable only with an electromyograph. The administration of 2,4-D at 1.3 or 1.0 mg/kg body weight failed to produce detectable EMG changes. One dog given dicamba at 86.7 mg/kg body weight developed clinical and EMG manifestations of myotonia similar to those induced by the highest doses of 2,4-D.

2,4-D toxicosis.II: A pilot study of clinical pathologic and electroencephalographic effects and residues of 2,4-D in orally dosed dogs.

English pointer dogs dosed po with encapsulated 2,4-dichlorophenoxyacetic acid (2,4-D) at 1.3, 8.8, 43.7, 175 or 220 mg/kg body weight failed to exhibit abnormalities in hematologic, serum biochemical, urinalysis, or electrocardiographic parameters. At the 3 lowest doses, no changes were noted in electro-encephalograms (EEGs). In the dog given 175 mg/kg, at 24 h postdosing mild sedation was accompanied by excessive slowing in the EEG with loss of low voltage fast activity. In the dog given 220 mg/kg, nonspecific alterations in the EEG suggestive of irritation and mild seizure activity was detected 7 h, but the EEG returned to normal by 24 h. A maximum 2,4-D concentration in serum of 1075 ppm was detected 5 h after a po dose of 220 mg/kg. A maximum 2,4-D, concentration in urine of 1792 ppm was detected 2 h after a po dose of 175 mg/kg, while 25 h after that dose kidney issue contained 271 ppm.

2,4-D toxicosis.III: An attempt to produce 2,4-D toxicosis in dogs on treated grass plots.

Eighteen English pointer dogs were randomly assigned to 3 outdoor grass-plot enclosures (6/enclosure) uniformly sprayed once with either the 2,4-dichlorophenoxyacetic acid (2,4-D) dimethylamine formulation (DMA-4) at the maximum recommended application rate, DMA-4 at 4 times the maximum recommended application rate, or the DMA-4 vehicle alone at 4 times the maximum recommended application rate. A heavy rain shower occurred 24 h after application. The dogs were observed for clinical signs and evaluated using an electroencephalograph, electrocardiograph (lead I), and electromyograph prior to exposure, and either 1 or 7 d after continuous exposure. Clinical examination, hematologic and serum biochemical data were obtained, and serum, urine and kidney 2,4-D were quantified. Half of the dogs from each group were killed after 1 d of continuous exposure, while the other half were killed after 7 d. Gross postmortem and histologic examinations were conducted on each dog. No obvious 2,4-D effects were detected in any of the dogs.