Could Zyrtec Have Caused an Arrhythmia in a Rhodesian Ridgeback?
by Carrie
(Shohola, PA)
It is now 4 months later. During his routine annual exam, the vet detected a heart arrythmia. An ECG confirmed a significant problem and we've been referred to a canine cardiologist. X-rays showed no enlargement of the heart.
One of the serious side-effects of Zyrtec is cardiac arrythmia -- found in 1% or less of those studied.
Ridgebacks are predisposed to DCM, but I see no mention of arrythmia in the breed as a recognized problem.
HOW POSSIBLE / PROBABLE IS IT THAT HIS SHORT DURATION ON ZYRTEC CAUSED THE ARRYTHMIA?
It's unlikely. Cetirizine (Zyrtec) is commonly used in dogs and heart rhythm problems aren't a commonly reported side effect in dogs at usual doses, and an arrhythmia found 4 months after stopping a short course is much more likely to have another cause.
Arrhythmias in large breeds can be an early sign of heart muscle disease such as dilated cardiomyopathy, sometimes before the heart enlarges, so the cardiology referral is the right step. A 24-hour Holter monitor and an echocardiogram will show the type of rhythm problem and whether the heart muscle is affected. Take the drug history with you to the cardiologist. Rhodesian Ridgebacks also have a recognized inherited ventricular arrhythmia, separate from DCM, so ask the cardiologist about it and about genetic testing.
See heart disease in dogs for more on DCM and arrhythmias.
This is general information, not a diagnosis. Please follow your own vet's advice.
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