Theophylline is a bronchodilator, which relaxes the airways and makes breathing easier. Theophylline is for dogs and cats. DIRECTIONS: Theophylline is given orally. Give the medication at the same time(s) every day to maintain a constant blood level. Always follow the dosage instructions provided by your veterinarian. If you have difficulty giving the medication, contact your veterinarian. SIDE EFFECTS: May cause loss of appetite, nausea, vomiting, diarrhea, or nervousness at the beginning of treatment. These side effects usually disappear after a short time. If they do not, or your pet has a rapid heartbeat, or an increase in appetite, drinking or urination, contact your veterinarian. May cause seizures at high doses. If so, contact your veterinarian immediately. May cause or worsen abnormal heart rhythms. If your pet experiences an allergic reaction to the medication, signs may include facial swelling, hives, scratching, sudden onset of diarrhea, vomiting, shock, seizures, pale gums, cold limbs, or coma. If you observe any of these signs, contact your veterinarian immediately. CAUTIONS: Theophylline is not for use in animals hypersensitive (allergic) to it or xanthines including theobromine and caffeine. Theophylline should not be used in animals hypersensitive to ethylenediamine. Use caution when using Theophylline in very young or obese animals; animals who are older or debilitated; or those that have severe heart disease, irregular heartbeats, stomach ulcers, hyperthyroidism, liver or kidney disease, hypoxia (lack of oxygen to the cells), high blood pressure, or a history of seizures.