Theophylline

(theophylline)

Brands

Slo-Phyllin, Elixophyllin (immediate-release liquids, tablets and capsules)

Availability

Theophylline tablets/capsules: 100 mg, 125 mg, 200 mg
Theophylline oral liquid, solution, syrup: 27 mg/5mL

Theophylline / Aminophylline equivalency

Aminophylline tablets: 100 mg (theophylline equivalent = 78.9 mg)
Aminophylline tablets: 200 mg (theophylline equivalent=158 mg)
Aminophylline injectable: 25 mg/mL (theophylline equivalent = 19.7 mg/mL)
Aminophylline oral liquid: 105 mg/5ml (theophylline equivalent = 90 mg/5ml)

Pharmacology

Theophylline is a methylxanthine derived from the group called Xanthines. The drugs theophylline and aminophylline are often spoken of together, though aminophylline is a derivative of theophylline, and differs somewhat in its structure from theophylline. Theophylline tends to be more potent and longer acting than aminophylline.

Drugs in the Xanthine group relax smooth muscle particularly bronchial muscle, stimulate cardiac muscle and the central nervous system, and produce diuresis. They also cross the placental barrier.

These drugs can be given orally, although absorption may be slow and not as effective as when given parenterally.

The methylxanthines are partly metabolized in the liver and excreted in the urine.

Indications

Used as a bronchodilator in reversible airway obstruction.

May be used in cases of Pulmonary edema and pulmonary congestion secondary to heart failure. Helpful in rats with CRD (chronic respiratory disease) and pneumonia.

Drug Interactions or Contraindications

Has synergistic toxicity with sympathomimetics such as ephedrine.
Erythromycin, ciprofloxacin/enrofloxacin, clindamycin, and other macrolides may increase aminophylline concentrations.

Adverse Reactions

CNS: nervousness,restlessness,seizures

CV: tachycardia,arrhythmias (increased and or irregular heart rate)

GI: gastric irritation

GU: polyuria (increased urine output)

Skin: pruritus (itching)

Dosage Recommendations

10 mg/kg, PO, q12hr ³⁷.

or

10 mg/kg to 20 mg/kg, PO, SQ, BID ³⁰

or

10 mg/kg to 20 mg/kg, PO, q8hr to q12hr ⁴¹^, ⁴²^, ⁴⁴

*Note, to veterinarians: see above under Availability for conversion of Theophylline/Aminophylline equivalency, or for dosing of aminophylline see link: aminophylline.

Considerations

In most cases serum levels do not need to be monitored in the pet rat. Fortunately, serum levels of theophylline have been found to correlate fairly equal, in dose dependent manner, with what is therapeutic and with what is toxic.
Make fluids, or juicy types of fruit available since theophylline will increase urine output.
Do not give chocolate, colas, or caffeine as this may increase the effect of the drug.
Can cause panic attack in rats because of its stimulant effect.
Use recommended nebulizers with a particle size of 0.5-5 micrometer when nebulizing bronchodilators, mucolytics or antimicrobials in rats. Nebulizers with a larger particle size that are used for humans, or small animals, will not be as effective in delivering the medication to the rat.
Theophylline injectable should be stored at 20°C to 25°C (68°F to 77°F), and protected from freezing and light. Injectables should not be used if it shows precipitate (crystals) in solution.
Store tablets at dry room temperature in closed container.
Store oral liquid or syrup at room temperature between 15°C to 30°C (59°F to 86°F). Do not freeze.

Consultant

Anthony Pilny, DVM, DABVP-Avian Certified | Avian & Exotic Pet Medicine and Surgery | The Center for Avian and Exotic Medicine
NYC, NY