Theophylline

PetMD’s medications content was written and reviewed by veterinary professionals to answer your most common questions about how medications function, their side effects, and what species they are prescribed for. This content shouldn’t take the place of advice by your vet.

What Is Theophylline?

Theophylline is a prescription medication that helps widen the airways to improve the flow of air into the lungs. This medication is used in dogs with tracheal, asthma or airway disease, and may be prescribed for cats with asthma. Although rare, theophylline may also be prescribed for horses with asthma.  

How Theophylline Works

Theophylline belongs to a class of medications called phosphodiesterase enzyme (PDE) inhibitors. Theophylline targets specific enzymes located on the airway muscles to help them widen and improve the flow of air into the lungs. It may also help the fine hairs (cilia) that line airways clear mucus more effectively and dry out excess mucus.

Theophylline is FDA-approved for human use under the brand names Elixophyllin® and Theo-24®, as well as the generic theophylline. Theophylline is currently not FDA approved as a veterinary medication. However, it is readily utilized in the veterinary field, and veterinarians can legally prescribe certain human drugs in animals in certain circumstances. This is called extra-label or off-label use because this use isn’t described on the drug label.

In certain circumstances, your vet may recommend a compounded formulation of Theophylline. Compounded medications are prescribed if there’s a specific reason your pet’s health can’t be managed by an FDA-approved drug, such as if your pet has trouble taking pills in capsule form, the dosage strength is not commercially available, or the pet is allergic to an ingredient in the FDA-approved medication. Compounded medications are not FDA-approved. They are created by either a veterinarian or a licensed pharmacist on an individual basis to best suit a patient’s particular needs. You can learn more about compounded medications here.

Theophylline Directions

Follow the directions on the drug label or as provided by your veterinarian. Theophylline can be given with or without food but giving with food can help prevent digestive upset.

Do not give theophylline with high fat foods like cheese or butter because this can increase the rate of absorption of certain theophylline formulations. This may lead to more severe side effects.

Missed a Dose?

If you forget to give a dose of theophylline, give it when you remember. However, if it is almost time for your next dose, skip the missed dose and resume your normal dosing schedule. Do not give extra or double doses.

Theophylline Possible Side Effects

Theophylline is generally well tolerated but side effects may include:

Vomiting

• Difficulty sleeping

• Diarrhea

• Increased appetite

• Increased thirst and urination

• Difficulty breathing

• Tremors

• Nervousness

• Elevated heart rate

Side effects in horses may include:

• Increased excitability

• Incoordination

• Excessive sweating

Human Side Effects

Theophylline is also a prescription medication for humans, frequently with dosages different from those prescribed for your pet by a veterinarian. Due to possible side effects, pets should not be given any medicine prescribed for humans. If you accidentally ingest a pet medication, call your physician or the national Poison Control Center hotline at 800-222-1222.  

Monitoring

No specific monitoring is required for this medication, but your veterinarian may recommend routine testing depending on your pets' individual needs, other medications they may be on and/or the issue that initially caused your pet to be placed on this medication.

Call Your Vet If:

• Severe side effects are seen (see above)

• You see or suspect an overdose

• You have additional questions or concerns about the use of theophylline

Theophylline Overdose Information

Overdoses of theophylline can be life threatening. Symptoms of an overdose may include elevated heart rates, abnormal heart rhythms, fever, electrolyte imbalances and seizures.

If you suspect an overdose, immediately contact your veterinarian or an animal poison control center. Consultation fees often apply.

Pet Poison Helpline (855) 764-7661

ASPCA Animal Poison Control (888) 426-4435

Theophylline Storage

Theophylline should be stored at controlled temperatures between 59–86 F.

Keep the container tightly closed in order to protect from moisture and light.

Compounded medications should be stored according to the compounding pharmacy’s label.

Keep out of reach of children and pets.

Theophylline FAQs

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