1. Clinical Overview
Doxofylline is a novel, selective xanthine derivative bronchodilator used primarily in the management of chronic obstructive pulmonary disease (COPD) and bronchial asthma. It is a methylxanthine derivative with a dioxolane group at position 7, which confers a distinct pharmacological profile compared to theophylline. It is known for its bronchodilatory and anti-inflammatory effects with a potentially improved safety and tolerability profile, particularly a lower incidence of central nervous system and cardiovascular side effects.
| Onset | Duration | Bioavailability |
|---|---|---|
| Within 30-60 minutes after oral administration. | Approximately 12 hours, supporting twice-daily dosing. | Approximately 62-75% following oral administration. |
2. Mechanism of Action
Doxofylline acts as a bronchodilator and possesses anti-inflammatory properties. Its primary mechanism is non-selective inhibition of phosphodiesterase (PDE) enzymes, particularly PDE III and PDE IV, leading to an increase in intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP) in bronchial smooth muscle cells and inflammatory cells. Elevated cAMP causes relaxation of bronchial smooth muscle. Unlike theophylline, it has very low antagonistic activity on adenosine receptors (A1 and A2).
3. Indications & Uses
- Chronic Obstructive Pulmonary Disease (COPD) maintenance therapy
- Bronchial Asthma (as a bronchodilator, especially for maintenance and prevention of symptoms)
4. Dosage & Administration
Adult Dosage: 400 mg orally twice daily (every 12 hours). The maintenance dose can range from 400 mg to 800 mg per day in divided doses.
Administration: Tablet should be swallowed whole with a full glass of water, with or without food. To minimize gastric upset, it can be taken after meals. Do not crush or chew sustained-release formulations if available. Maintain consistent timing of doses.
5. Side Effects
Common side effects may include:
- Nausea
- Headache
- Epigastric pain/discomfort
- Heartburn
- Insomnia
- Nervousness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Ciprofloxacin, Enoxacin | May increase doxofylline levels by inhibiting its metabolism. Risk of toxicity. | Major |
| Erythromycin, Clarithromycin | May increase doxofylline levels. Monitor for side effects. | Moderate |
| Allopurinol | May increase doxofylline levels. | Moderate |
| Beta-2 Agonists (Salbutamol, Formoterol) | Additive bronchodilatory effect; may potentiate hypokalemia and tachycardia. | Moderate |
| Diuretics (Furosemide) | Increased risk of hypokalemia. | Moderate |
| Phenytoin, Carbamazepine, Rifampicin | May decrease doxofylline levels by inducing metabolism, reducing efficacy. | Moderate |
| Warfarin | Potential increased anticoagulant effect; monitor INR. | Moderate |
7. Patient Counselling
- DO take the medicine at the same time(s) each day to maintain steady levels.
- DO inform your doctor about all other medicines, including OTC and herbal products.
- DO report any persistent nausea, palpitations, or severe headache.
- DO keep your follow-up appointments for asthma/COPD management.
- DONT stop taking this medicine suddenly without consulting your doctor.
- DONT take extra doses if you miss one. Take the next dose at the regular time.
- DONT crush or chew sustained-release tablets (if prescribed).
- DONT consume excessive caffeine (coffee, tea, cola) while on this medication.
8. Toxicology & Storage
Overdose: Symptoms are primarily extensions of pharmacologic effects and side effects: Severe nausea/vomiting, agitation, restlessness, tremors, tachycardia, cardiac arrhythmias (supraventricular and ventricular), hypotension, seizures, hyperglycemia, hypokalemia. In extreme cases, it can lead to cardiorespiratory arrest.
Storage: Store below 30°C in a cool, dry place, protected from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.