Clinical effects and plasma concentration determination after 2,4-dichlorophenoxyacetic acid 200 mg/kg administration in the dog.
OBJECTIVE
To investigate the clinical effects and to determine the 2,4-dichlorophenoxyacetic acid plasma concentrations after a dose of twice the reported LD50 (100 mg/kg) was administered orally to dogs. Investigation included electromyographic evaluations and biochemical parameter determinations, as well as observable clinical signs.


METHODS
Six beagle dogs were administered 2,4-dichlorophenoxyacetic acid 200 mg/kg orally. Dogs were monitored for the development of clinical signs and were anesthetized at 24 hours for needle electromyography. Blood was collected pre- and 24-hours postadministration. Plasma was analyzed for total and unbound 2,4-dichlorophenoxyacetic acid by high-performance liquid chromatography with fluorescence detection. Serum was submitted for clinical chemistry parameter analysis. Statistical analyses of the chemistry parameters were performed using paired t-tests.


RESULTS
All 6 dogs survived after oral administration of twice the reported LD50. Clinical signs observed were vomiting in 33% and diarrhea in 100% of the dogs. No gait abnormalities were seen in awake dogs. Electromyographic findings revealed predominantly insertional myotonia with 1 dog having spontaneous fibrillations. Decreases from baseline measurements were seen in serum calcium, potassium, and total bilirubin. The mean total and unbound plasma 2,4-dichlorophenoxyacetic acid concentrations were 511 mg/L and 129 mg/L, respectively.


CONCLUSIONS
This study demonstrates that the beagle dog is less sensitive to the acute effects of 2,4-dichlorophenoxyacetic acid than previously reported. The main clinical effects seen after oral administration of twice the reported LD50 were vomiting and diarrhea. Total and unbound plasma 2,4-dichlorophenoxyacetic acid concentrations may be a useful indicator of toxicity.
Dickow
L M
LM
The Ohio State University, College of Veterinary Medicine, Columbus, USA.
Podell
M
M
Gerken
D F
DF
D015084:2,4-Dichlorophenoxyacetic Acid / Q000008:administration & dosage / Q000097:blood* / Q000633:toxicity*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003967:Diarrhea / Q000139:chemically induced; D004285:Dogs; D004576:Electromyography; D005260:Female; D006540:Herbicides / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity*; D007928:Lethal Dose 50; D009222:Myotonia / Q000139:chemically induced; D014839:Vomiting / Q000139:chemically induced
D006540:Herbicides; D015084:2,4-Dichlorophenoxyacetic Acid