Long-Term Drug Study Uncovers 35% Abnormal Test Results
By Ernest E. Ward Jr., DVM

A recent IDEXX study of 2,943 pets that received at least one long-term medication, found 34.6% had at least one abnormal laboratory test result. This finding underscores the importance of performing routine monitoring blood tests on patients receiving long-term medications. The most commonly prescribed medications included in this study were carprofen, etodolac, methimazole, phenobarbital, enalapril, furosemide and levothyroxine sodium. The study found no single drug elicited an unusually high number of abnormal test results. Rather, the even distribution of abnormal findings among all drugs tested suggested pets undergoing long-term medical treatments often had secondary or emerging diseases that were only identified when blood tests were performed.

The majority of pets that had abnormal laboratory findings were 7 years of age and older. This corroborates other scientific data indicating that older patients receiving long-term drug treatments must be closely monitored to ensure normal organ function. Older pets have a higher likelihood of decreased liver or kidney function, which increases their risk of drug-related adverse events. Additionally, this study suggests that organ function may potentially decline over time and any changes must be recognized as early as possible to prevent any drug-related issues. Routine follow-up blood and urine tests every 3 to 6 months is generally accepted as adequate to recognize any developing organ system compromise.

One of the interesting highlights of the study indicated that older mixed-breed dogs were as likely to have an abnormal laboratory test finding as older pure-breed dogs. This reinforces the long-standing belief that most drug-related issues are as much age-related as breed-predisposed. The benefits of testing all pets that receive long-term drugs, regardless of breed, were well-substantiated in this study. If a doctor chooses only to test breeds reported to be at risk for certain medications, they may place their mixed-breed patients at risk.

As more and more medical treatments for chronic diseases become available for pets, veterinarians must ensure they are performing due diligence to protect the health and welfare of their patients. This study proved that more than one-third of pets receiving at least one long-term medication had an abnormal laboratory test result. Through early recognition of a change in organ system function, the veterinarian can alter the treatment course to avoid potential adverse drug events. Failure to recognize a drug-related problem can result in irreversible organ damage and even death. Veterinarians can often improve the quality of life of their patients by diagnosing secondary emerging diseases early in their course and improve the chances of successful treatment.

Accompanying each new medical advance is the revelation that new monitoring protocols must be created. We are now well into the age of long-term medical treatments in veterinary medicine. This new era in treatment has brought about the need to perform routine follow-up blood and urine testing to help prevent any inadvertent harm. Today’s pets are living longer, healthier and more comfortable lives than ever before, thanks to medical breakthroughs. We owe it to them to follow the Hippocratic Oath and “do no harm.” Long-term drug monitoring can help us fulfill that promise.

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