Urine Drug Screens for Pets: What You Need to Know

A patient with acute onset neurologic signs walk into your clinic and the owner admits the dog could have been exposed to illicit drugs.

Should you run an over-the-counter urine drug screen? What if the results aren’t what you expect?

The ASPCA Animal Poison Control Center explains the ins and outs of urine drug screens and how to get the best answers from them.

An OTC urine drug screen can be a useful diagnostic tool when treating toxicity or suspected toxicity cases in veterinary medicine. The tests are readily available, affordable and offer rapid results.

When to Use Urine Screens

It's important to know when best to use them. They can be helpful when:

• Signs are consistent with an illicit drug but owners are reluctant to admit potential exposure
• A patient potentially had access to an illicit drug and is exhibiting suspicious signs
• A patient may have been exposed to multiple drugs
• Signs the patient is exhibiting are not consistent with what is expected

Most of the information available regarding these tests are based on literature from humans. One study with dogs did show that at least one type of urine drug screen correctly identified barbiturates, opiates, benzodiazepines and amphetamines/methamphetamines. This study also found that neither the OTC test nor gas chromatography mass spectrometry at standard settings identified methadone or marijuana in dogs known to have been exposed.

While the exact reason for these false negatives is not known, a possible reason may be dogs produce different metabolites than typically tested for in humans. 

False Positives

False positives can make testing a challenge. In humans, false positives are often due to drugs that are structurally similar to the drug being tested for. Here are a few areas where false positives may occur based on human data:

• THC can be mimicked by ibuprofen, naproxen, proton pump inhibitors and hemp-containing foods
• Amphetamines/methamphetamines may be mimicked by trazodone, phenylpropanolamine, ranitidine, chlorpromazine, doxepin, fluoxetine, selegiline, amantadine, aripiprazole, bupropion, pseudoephedrine, phenylephrine and atomoxetine
• TCA may be mimicked by carbamazepine, cyclobenzaprine and quetiapine
• Benzodiazepines may be mimicked by sertraline
• Opiates may be mimicked by naloxone, diphenhydramine, quinolone antibiotics (levofloxacin, ciprofloxacin), quetiapine, rifampicin, tramadol, verapamil, dextromethorphan and poppy seeds
• PCP may be mimicked by tramadol, diphenhydramine, ketamine, lamotrigine, venlafaxine, dextromethorphan, doxylamine and ibuprofen
• LSD may be mimicked by amitriptyline, chlorpromazine, diltiazem, doxepin, fentanyl, fluoxetine, metoclopramide, trazodone, bupropion, buspirone, risperidone, sertraline, verapamil and methylphenidate
• Barbiturates may be mimicked by ibuprofen and naproxen
• Tests for cocaine tend to be very accurate but cocaine is typically adulterated and at least one of it known adulterants, diltiazem, may show up positive for LSD

False positives are not the only potential complicating factor. The patient must have been exposed to a sufficient amount of drug and adequate time needs to elapse from the exposure for the drug to be in the urine. Specimen handling should also be considered, as some drugs like THC may adhere to glass or rubber. 

For more information, read the Top 5 Tips for Treating Illicit Drug Exposures and listen to a free, recorded webinar by the APCC on the Toxicology of Illicit Drug Exposures.