Monday October 11th: What More Do You Want?
October 11, 2021
Over the counter drugs and products to avoid for your pets: Pt 2
October 11, 2021

Over the counter drugs and products to avoid for your pets: Pt 1

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By Dr Asia O’Neill

The animals of God’s creation inhabit the skies, the earth and the sea. and have a part in human life. We, therefore, invoke God’s blessing on these animals. over all the creatures of the earth—St Francis of Asissi

There are many over-the-counter (OTC) drugs that are easily accessible and seem simple enough to be used for human consumption. However, even though these drugs are used with little to no harm in regular use by us, it may not be so harmless for use in certain pets. Usage of drugs that are considered to be ‘off label’ or ‘extra-label’ should only be after consulting with a veterinarian to ensure safe administration. Carefully considering what can be safely given to your pets will prevent toxic effects from occurring.


Acetaminophen is the active ingredient in Tylenol, Paracetamol and Panadol and is used for pain relief and fever reduction in humans. Acetaminophen may be the sole ingredient or part of a combination product containing other medications. These medications may include aspirin, opioids, antihistamines, decongestants, and caffeine.

Low doses of acetaminophen can be given only under the direction of a veterinarian. The metabolism of acetaminophen differs in dogs and cats than in humans. This means that relatively small doses, may be toxic to them. Cats are especially sensitive to acetaminophen as they have less functional cellular pathways for the metabolism for certain drugs, including acetaminophen. Since cats cannot efficiently metabolise acetaminophen, they are more susceptible to poisoning. Cats can develop intoxication at much lower doses than dogs.

No signs may be seen initially, however, Acetaminophen can cause liver damage or decrease the red blood cell’s ability to carry oxygen, due to methemoglobinemia. Cats are more likely to develop early damage to the red blood cells while dogs are more likely to develop liver damage. However, either of these conditions, or both, can manifest due to toxicity in either species.

Damage to the red blood cells occurs within 4-12 hours with toxicity. Lethargy, weakness, inappetence, rapid breathing, a high heart rate, panting, abdominal pain, vomiting, or drooling can develop as signs. Mucous membranes, including the gums or conjunctiva, may become cyanotic, giving a blue appearance. Methemoglobin accumulating in these areas can also result in a chocolate brown colour. Facial swelling or swelling of the paws and forelimbs several hours after ingesting acetaminophen can also occur with toxicity.

Liver damage may be delayed for several days. In addition to the signs above, dark urine, jaundice of the eyes or skin, an enlarged abdomen, increased drinking, and urination or discolored feces may be seen. If these signs are not recognised and treated, death may occur.

Dry eye (keratoconjunctivitis) can also be a result of toxicity resulting in squinting, discharge, and ocular pain. If the ingested acetaminophen was combined with other medications, additional signs may occur. These may include incoordination, weakness, depression, hyperactivity, agitation, disorientation, vocalizing, changes in heart rate, pale gums, tremors, seizures, or fever.



Aspirin or acetylsalicylic acid is a non-steroidal, anti-inflammatory drug for pain control and fever reduction. It is most commonly used for its anti-clotting effects in many pets. Its use in different animal species is ‘off label’ or ‘extra label’. This should strictly be done under the direction of a veterinarian.

The side effects most commonly seen are gastrointestinal, such as nausea, decreased appetite, vomiting, or intestinal irritation. Bleeding of the gastrointestinal (GI) tract, due to ulceration may also occur, even at the therapeutic dose. It will result in black/tarry stools, blood or ’coffee grounds in the vomit, or stooling of frank blood. Anemia and low blood protein can develop as a result of severe gastric bleeding. In cats, aspirin may lead to acidosis. The effects of aspirin usually last for few days, although effects can be longer in pets with liver or kidney disease. As such, doses in said patients should be avoided.

Cats are also very sensitive to aspirin because clearance occurs at a much slower rate from their system. If dosed incorrectly, it can accumulate and cause toxic effects, resulting in kidney and liver damage.

Aspirin should not be used in pets that are allergic to it, or pets that have bleeding ulcers, bleeding disorders, asthma, or kidney failure. Use caution in pets that have severe liver failure, decreased kidney function, or have low blood protein. If possible, aspirin should not be used one week prior to surgical procedures.

It must be used cautiously and dosed very carefully in cats and newborn pets. Aspirin should not be used in pregnant animals unless it is a last resort.