Abstract
A seven-year-old spayed female Golden Retriever that presented with dilated cardiomyopathy with fainting episodes was treated with Mexiletine (3 mg/kg, q12 h). The canine achieved remission of the clinical symptoms for more than one year under this treatment regimen. However, when the canine started to have fainting spells again caused by ventricular tachycardia and premature ventricular contraction, the blood concentration of Mexiletine was checked. It was found to be below the effective level. Therefore, the dosing interval was shortened (3 mg/kg, q8 h) to maintain an effective blood concentration of the drug, and the fainting episodes abated. These results suggest that in patients on Mexiletine, the blood concentration of Mexiletine should be measured when indicated by the clinical signs, and the dosage adjusted according to the measurement results.
