Theophylline / Aminophylline

What is this medication for?

• Bronchodilation (chronic bronchitis, tracheal collapse adjunct); adjunct in acute pulmonary edema with bronchoconstriction; mild diuretic effect
• Feline asthma/bronchitis bronchodilation; adjunct in fulminant CHF bronchoconstriction

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• stomach/intestinal: vomiting, diarrhea, ↑ gastric acid (Level-related; often transient at therapy start)
• CNS stimulation, insomnia, restlessness (Level-related)
• Polyphagia/drinking more than usual/urinating more than usual (Common)

Worth a phone call to your veterinarian

• Any new symptom that worries you.

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Seizures, cardiac arrhythmias, overheating (Severe intoxication (>20 micrograms/mL human threshold; dogs tolerate higher))

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Xanthine hypersensitivity (theobromine, caffeine); ethylenediamine sensitivity (aminophylline)
• has or has had: Severe cardiac disease/arrhythmias, seizure disorders, gastric ulcers, hyperthyroidism, renal/hepatic disease, severe hypoxia, severe high blood pressure; neonatal/geriatric patients (↓ clearance); CHF (prolonged half-life)

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Erythromycin, fluoroquinolones (enrofloxacin), cimetidine, ketoconazole
  • Phenobarbital, rifampin (CYP inducers)
  • Beta-agonists (albuterol)
  • Furosemide, phenylbutazone, probenecid, caffeine, acetaminophen

Storage and handling

Room temperature. Aminophylline dose ↔ theophylline dose interconvert via the 79% theophylline fraction.

Good to know

• Dogs tolerate levels toxic to humans — but seizures and arrhythmias still occur in severe intoxication: treat with gut emptying + charcoal, diazepam (seizures), propranolol (life-threatening unusually fast heart rate).
• Inhaled bronchodilators (albuterol) have largely replaced oral theophyllines for feline asthma maintenance — theophylline persists mainly as an oral adjunct or where inhalation is impossible.
• Sustained-release product choice matters (30–76% bioavailability spread) — don't switch products without re-titration.
• Aminophylline into a muscle causes intense local pain — use by mouth or into a vein (slow).