Major Uses

Theophylline belongs to the methylxanthine group of drugs and is chemically related to caffeine. The medication treats various conditions and diseases by increasing contraction strength of the diaphragm, dilating and relaxing constricted airways, stimulating the central nervous system, and increasing the beat frequency of cilia in the respiratory tract. It also functions as a diuretic. These actions make theophylline an effective treatment for asthma, sleep apnea, heart failure, bronchitis, and other chronic lung diseases.

Theophylline is an important drug in the treatment of respiratory problems in cats and dogs. It is not approved by the Food and Drug Administration for use in animals, but it is prescribed legally as an extra-label drug by veterinarians.

Common Precautions

Side effects associated with use of theophylline are many and varied. Caffeine-type jitters and restlessness are most commonly reported, and the drug may also cause upset stomach, increased urination, racing heart rate, abnormal heart rhythm, and others. These side effects typically do not occur in dogs, however, until the dose of medication is very high. Theophylline is known to increase heart rate, which can exacerbate some types of heart arrhythmias and interfere with the heart's ability to fill properly. Cats suffering from hyperthyroidism or hypertrophic cardiomyopathy are at greatest risk for these adverse effects.

Theophylline should be avoided in animals with a tendency of cardiac arrhythmias. It should also be used with caution in dogs and cats with high blood pressure, liver disease, or pre-existing ulcers. Animals prone to seizures may experience a worsening of their condition while undergoing treatment with theophylline.

The medication is able to cross the placenta and should therefore only be used during pregnancy if instructed by a veterinarian. It also passes into the milk of nursing mothers.

Theophylline may interact with other drugs and supplements, including enrofloxacin, clindamycin, allopurinol, lincomycin, phenobarbital, ketoconazole, acetaminophen, furosemide, beta blockers, and erythromycin.

Theophylline should not be used in animals with a known allergy or hypersensitivity to the drug. The medication may cause seizures when taken at high doses. Any known or suspected overdose should be reported to a veterinarian right away.


Theophylline should be stored in the original packaging, at room temperature, and away from children and animals.


Theophylline is available as 100 mg, 200 mg, and 300 mg tablets. It may also be available in other formulations or strengths. In dogs, theophylline is typically dosed at 3 to 5 mg/lb (6 to 10 mg/kg) three times daily. In cats, the drug is typically dosed at 2 mg/lb (4 mg/kg) one to three times daily. Once daily dosing in cats is usually done at night.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

If a dose of theophylline is missed, it should be given as soon as possible. If it is almost time for the next dose, the missed dose should be skipped. Two doses of this medication should not be given at once.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.