What is pentoxifylline?
Pentoxifylline (brand names: Trental®, PTX) is an immunomodulatory agent used to treat certain immune-mediated skin conditions and inflammation of the blood vessels that lead to poor blood flow, including ear margin dermatitis and cutaneous lupus in dogs, and navicular disease in horses.
Its use in cats, dogs, and horses to treat skin and vessel disease is off label (extra label). Many drugs are commonly prescribed for off-label use in veterinary medicine. “Off label” means the drug is being used in a way that has not been reviewed or approved by the U.S. Food and Drug Administration (FDA) or Health Canada.
In these instances, follow your veterinarian’s directions and cautions carefully, as they may be significantly different from those on the label.
How is pentoxifylline given?
- Pentoxifylline is given by mouth in the form of a tablet. It may also be specially compounded into a liquid form.
- Measure liquid forms carefully.
- Give with food.
This medication should take effect within 1 to 2 days, and improvements in clinical signs should follow.
What if I miss giving my pet the medication?
If you miss a dose, give it as soon as you remember, and then continue with the regular dosing schedule. However, if it is almost time for the next dose, skip the missed dose and resume the regular dosing schedule. Do not give the pet two doses at once.
Are there any potential side effects?
The most common side effects include:
- Vomiting
- Diarrhea
- Lack of appetite
- Excitement
- Restlessness
Serious adverse reactions may occur. If any of the following signs develop, stop giving pentoxifylline and contact your veterinarian immediately:
- Seizures
- Collapse
- Fever
- Severe skin rashes
Drug sensitivities can develop over time, with repeated exposure. Your pet may have no reaction after the first few doses but may develop a sensitivity later. It is important to watch for signs of an allergic reaction over the entire course of treatment (e.g., irregular breathing, rash, fever, puffiness and swelling around the face) and notify your veterinarian if you have any concerns.
Other side effects may occur. If you notice anything unusual, contact your veterinarian immediately. This short-acting medication should stop working within 24 hours, although effects can be longer in pets with liver or kidney disease.
Are there any risk factors for this medication?
DO NOT USE pentoxifylline in:
- Pets that are allergic to it or allergic to xanthines
- Pets with bleeding in the brain or the eye
USE WITH CAUTION in:
- Pets with severe liver or kidney disease
- Pets at risk of bleeding
USE WITH EXTREME CAUTION in:
- Pets that are pregnant or nursing
Are there any drug interactions I should be aware of?
Several medications should be used with caution when given with pentoxifylline, including:
- Antihypertensive drugs
- Insulin
- Nonsteroidal anti-inflammatory drugs (NSAIDs)
- Platelet-aggregation inhibitors
- Theophylline
Pentoxifylline may also interact with skin allergy testing; discontinue this medication at least one week prior to allergy testing.
Be sure to tell your veterinarian about any medications (including vitamins, supplements, or herbal therapies) that your pet is taking before starting any treatment.
Is any monitoring needed with this medication?
- Your veterinarian will let you know when and how they want to reassess your pet to ensure the medication is working and not causing side effects.
- At home, monitor for any side effects such as those noted above. If any occur, stop using the medication and contact your veterinarian.
- If bleeding is suspected, your veterinarian may monitor blood cell counts.
How do I store pentoxifylline?
- Store the tablets at room temperature between 68°F and 77°F (20°C and 25°C), protected from light.
- Keep the container out of reach of children and pets. 
What should I do in case of emergency?
If you suspect an overdose or an adverse reaction to the medication, call your veterinary office immediately. If they are not available, follow their directions in contacting an emergency facility. Be prepared to provide information about the product and your pet’s weight and symptoms.
