# Theophylline: veterinary dose and monograph

> Theophylline is a veterinary drug. Methylxanthine bronchodilator — relaxes airway smooth muscle, mildly improves diaphragmatic function and mucociliary clearance, and has a weak respiratory-stimulant effect. Indications include chronic bronchitis (canine); feline asthma / lower-airway disease (adjunct); bronchospasm with reversible airway disease. This monograph lists 6 reference doses for dogs, cats, horses and ferrets, each with route, frequency and source.

Source: https://vetmasterji.com/drugs/theophylline · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Veterinary drug
- **Also known as:** Theo-Dur, Deriphyllin
- **Species with doses:** Dogs, Cats, Horses and Ferrets
- **General dose range:** 4–19 mg/kg PO q12–24h (sustained-release) — check the species tables for the indication
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Chronic bronchitis (canine)
- Feline asthma / lower-airway disease (adjunct)
- Bronchospasm with reversible airway disease

## Theophylline dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Theophylline doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Bronchodilation (sustained-release) | 10 mg/kg | PO | q12h | — |
| Immediate-release theophylline | 9 mg/kg | PO | q8h | — |

- Bronchodilation (sustained-release): Papich 5e and Plumb’s p.72 (Bach 2004): extended-release 10 mg/kg PO q12h, increasing to 15 mg/kg q12h if no adverse effects and inadequate response. Narrow therapeutic index — dose on lean weight; fluoroquinolones and other CYP inhibitors raise levels.
- Immediate-release theophylline: Papich 5e: immediate-release theophylline 9 mg/kg q8h PO.

### Cats

*Theophylline doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Asthma / bronchitis (sustained-release) | 20–25 mg/kg | PO | q24h in the evening | — |
| Immediate-release theophylline | 4 mg/kg | PO | q8–12h | — |

- Asthma / bronchitis (sustained-release): Papich 5e: sustained-release tablets 20 mg/kg (100 mg per cat) q24h, or ER capsules 25 mg/kg (125 mg per cat) q24h PO; interval may be extended to q48h long-term. Plumb’s p.72 (Johnson 2000): 20–25 mg/kg PO once daily in the evening. Evening dosing gives best absorption in cats.
- Immediate-release theophylline: Papich 5e: immediate-release theophylline 4 mg/kg q8–12h PO. (For aminophylline doses see the Aminophylline entry — aminophylline is about 80% theophylline.)

### Horses

*Theophylline doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Equine asthma (RAO) | 5 mg/kg | PO | q12h | — |

- Equine asthma (RAO): Papich 5e: theophylline 5 mg/kg q12h PO; aminophylline 12 mg/kg initially then 5 mg/kg q12h. Plumb’s p.72: aminophylline 5–10 mg/kg PO or IV twice daily (Lavoie 2003). IV use causes transient excitement — dilute and give slowly (≤25 mg/min). ARCI Class 3.

### Ferrets

*Theophylline doses for ferrets*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Bronchodilation | 4.25 mg/kg | PO | q8–12h | — |

- Bronchodilation: Plumb’s p.72 (Williams 2000): 4.25 mg/kg PO two to three times daily.

## Contraindications

Tachyarrhythmia, seizure disorders, significant cardiac disease. Many interactions (fluoroquinolones, cimetidine, fluvoxamine raise levels). Reduce dose in hepatic / cardiac failure and in the elderly.

## Adverse effects

- GI upset, vomiting
- CNS stimulation — restlessness, hyperexcitability, tremor
- Tachycardia, arrhythmia; seizures with toxicity

## Drug interactions

- Fluoroquinolones (enrofloxacin, ciprofloxacin), cimetidine, fluvoxamine, macrolides: inhibit metabolism → raised levels / toxicity — reduce dose
- Phenobarbital / rifampin: induce metabolism → lower levels
- Beta-agonists (terbutaline): additive cardiac and hypokalaemic effects
- Halothane: increased arrhythmia risk

## Pregnancy and lactation

Crosses the placenta and enters milk; use in pregnancy only if benefit outweighs risk.

## Monitoring

- Heart rate / rhythm and CNS / GI signs of toxicity
- Serum theophylline level where available (target ~5–20 µg/mL)
- Review co-medications that alter its metabolism

## Toxicity and overdose

Narrow therapeutic index — toxicity causes vomiting, tachyarrhythmia, hyperexcitability, tremor, hypokalaemia and seizures, sometimes before milder warning signs.

Management: Stop the drug; control seizures (diazepam), manage tachyarrhythmia (beta-blocker / lidocaine), correct hypokalaemia and give IV fluids; multi-dose activated charcoal enhances elimination. Monitor ECG and potassium.

## Clinical pearls

- A bronchodilator adjunct, not a substitute for the corticosteroid that treats the underlying airway inflammation
- Do not interchange immediate- and sustained-release products milligram-for-milligram — the kinetics differ
- Watch for additive toxicity when starting a fluoroquinolone or cimetidine — they raise theophylline levels

## Mechanism of action

Methylxanthine. Non-selectively inhibits phosphodiesterase (raising intracellular cyclic AMP) and antagonises adenosine receptors, producing bronchial smooth-muscle relaxation, improved diaphragmatic contractility, mild diuresis, and CNS / cardiac stimulation.

## Formulations and products

- Theophylline sustained-release 100 mg tablet
- Theophylline sustained-release 200 mg tablet
- Deriphyllin — Etofylline 84.7 mg + theophylline 25.3 mg, Tablet / injection (combination) (human-label)
- Theophylline SR (generic) — 100 / 200 / 300 mg, Sustained-release tablet (human-label)

## Storage

Store at 15–30 °C, dry; keep sustained-release tablets intact.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

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## Frequently asked questions

### What is the dose of Theophylline for dogs?

Reference doses for Theophylline in dogs: 10 mg/kg PO q12h (Bronchodilation (sustained-release)); 9 mg/kg PO q8h (Immediate-release theophylline). Confirm against the label and the patient before use.

### What is the dose of Theophylline for cats?

Reference doses for Theophylline in cats: 20–25 mg/kg PO q24h in the evening (Asthma / bronchitis (sustained-release)); 4 mg/kg PO q8–12h (Immediate-release theophylline). Confirm against the label and the patient before use.

### What is the dose of Theophylline for horses?

Reference doses for Theophylline in horses: 5 mg/kg PO q12h (Equine asthma (RAO)). Confirm against the label and the patient before use.

### When should Theophylline not be used?

Tachyarrhythmia, seizure disorders, significant cardiac disease. Many interactions (fluoroquinolones, cimetidine, fluvoxamine raise levels). Reduce dose in hepatic / cardiac failure and in the elderly.

### What are the side effects of Theophylline in animals?

GI upset, vomiting; CNS stimulation — restlessness, hyperexcitability, tremor; Tachycardia, arrhythmia; seizures with toxicity.

## Sources

- Plumb's Veterinary Drug Handbook
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.