Doxofyl100 mg/5 ml

Established use

Doxofyl is indicated for the symptomatic maintenance treatment of reversible airway obstruction associated with:

• Bronchial asthma (chronic/persistent asthma)
• Chronic obstructive pulmonary disease (COPD)
• Chronic bronchitis and other pulmonary disease with a spastic bronchial component

Adjunct / lower-evidence use

Doxofyl has also been used in some markets as an adjunct in bronchiectasis with reversible airway obstruction; this use has a lower strength of evidence than its role in asthma and COPD.

Doxofyl is a maintenance bronchodilator for chronic, reversible airway disease; it is not intended for relief of acute bronchospasm or status asthmaticus, for which fast-acting rescue bronchodilators are preferred.

Doxophylline is marketed in Bangladesh and other countries in several oral dosage forms and strengths:

• Tablets: 200 mg and 400 mg Doxophylline
• Sustained-release (SR) tablets: 400 mg Doxophylline
• Syrup: commonly 50 mg/5 mL Doxophylline (pediatric-friendly liquid formulation)

Each formulation also contains standard pharmaceutical excipients; exact excipients vary by manufacturer and brand.

Doxofyl is a xanthine-derivative bronchodilator structurally related to theophylline, distinguished by a dioxolane group at position 7 of the xanthine ring. It is used for the long-term, maintenance management of reversible airway obstruction in asthma and chronic obstructive pulmonary disease (COPD).

Compared with theophylline, Doxofyl has substantially lower affinity for adenosine A1/A2 receptors, which is proposed to explain the more favorable cardiac and central nervous system side-effect profile reported for Doxofyl in some clinical studies, while retaining a bronchodilator effect thought to be mediated mainly through phosphodiesterase inhibition. Doxofyl is widely marketed in Bangladesh, India, Italy, and other countries as tablets, sustained-release tablets, and syrup; it is not an antibiotic.

Doxofyl belongs to the therapeutic class of Xanthine derivative bronchodilators, a group of medicines used to relax airway smooth muscle and relieve reversible airflow obstruction in chronic respiratory disease.

Doxophylline is a methylxanthine bronchodilator that differs from theophylline by the addition of a dioxolane group at the 7-position of the xanthine nucleus. Its bronchodilator action is attributed mainly to non-selective inhibition of phosphodiesterase (PDE) enzymes in airway smooth muscle, which raises intracellular cyclic AMP and produces bronchial smooth muscle relaxation; Doxophylline may also reduce platelet-activating factor and leukotriene generation, contributing to a mild anti-inflammatory effect.

Unlike theophylline, Doxophylline has markedly reduced affinity for adenosine A1 and A2 receptors. Because many of the cardiac (tachycardia, arrhythmia) and central nervous system (tremor, insomnia, seizure) effects of xanthines are linked to adenosine receptor antagonism, this reduced affinity is proposed to underlie the comparatively better tolerability reported for Doxophylline versus theophylline in some studies, although Doxophylline can still cause these effects, particularly at higher doses or in susceptible patients.

Doxophylline is absorbed orally and metabolized mainly in the liver; clearance can be reduced by hepatic impairment, cardiac disease, advanced age, or concomitant use of certain drugs (see Interaction), and increased by smoking and some enzyme-inducing drugs.

Doxofyl tablets, including sustained-release tablets, should be swallowed whole with a glass of water; sustained-release tablets must not be crushed, chewed, or split. Doxofyl syrup should be measured accurately using the measuring cup or spoon supplied with the product. Doxofyl is best taken with or shortly after meals to minimize gastrointestinal irritation, and doses should be spaced evenly through the day as directed by the prescribing physician to maintain steady blood levels.

Doxofyl undergoes hepatic metabolism and can interact with several other drugs and substances:

• Other xanthine derivatives (e.g. theophylline, aminophylline): concurrent use with Doxofyl should be avoided, as it increases the risk of additive xanthine toxicity (tachycardia, arrhythmia, seizures).
• Macrolide antibiotics (e.g. erythromycin), lincosamides, cimetidine (H2-blockers), allopurinol, and propranolol: these can reduce the hepatic clearance of Doxofyl and raise its blood levels, increasing the risk of side effects; dose adjustment or closer monitoring may be needed.
• Sympathomimetic agents (e.g. ephedrine) and other bronchodilators: combined use with Doxofyl may increase the risk of cardiovascular stimulation (tachycardia, palpitations) and should be undertaken with caution.
• Phenytoin, rifampicin, and cigarette smoking: these can increase hepatic clearance of Doxofyl, potentially reducing its effectiveness and requiring dose adjustment.
• Caffeine and other xanthine-containing foods/beverages: high intake should be limited during treatment with Doxofyl, as they may add to xanthine-related stimulant effects.

Patients should inform their physician of all medicines, supplements, and herbal products they are taking before starting Doxofyl.

Common

• Nausea, vomiting, epigastric pain
• Headache
• Insomnia, irritability, restlessness

Less common

• Tachycardia, palpitations, extrasystoles
• Tachypnea

Rare

• Hyperglycemia
• Albuminuria
• Hypersensitivity reactions (e.g. skin rash)

Patients should seek medical attention if severe palpitations, chest pain, seizures, or signs of a severe allergic reaction occur while taking Doxofyl.

Doxofyl should be used during pregnancy only if clearly needed and if the potential benefit justifies the potential risk to the fetus. Animal reproduction studies have not shown adverse effects on pre- and postnatal development, but clinical data in pregnant women are insufficient to establish safety; a physician should always be consulted before using Doxofyl during pregnancy.

Doxofyl is generally considered contraindicated during breastfeeding, as xanthine derivatives are known to pass into breast milk and data specific to Doxofyl are insufficient to establish safety in nursing infants; breastfeeding mothers should not use Doxofyl without explicit medical advice, and an alternative may be preferred.

Use Doxofyl with caution in the following situations:

• Cardiac arrhythmia, ischemic heart disease, hypertension, or congestive heart failure.
• Hyperthyroidism.
• Uncontrolled seizure disorders or a history of seizures.
• Peptic ulcer disease.
• Severe hypoxemia, chronic pulmonary disease, or hepatic impairment, all of which can alter clearance of Doxofyl and require dose reduction (see Use in Special Populations).
• Renal impairment, where monitoring is advised.

Elderly patients generally require a lower dose of Doxofyl owing to reduced hepatic clearance. Concurrent use with other xanthine-class drugs should be avoided (see Interaction). Doxofyl is not associated with a known risk of dependence or addiction. Patients should stop Doxofyl and seek medical care if palpitations, chest pain, seizures, or signs of a severe allergic reaction develop.

Overdose of Doxofyl can cause severe cardiac arrhythmias and tonic-clonic seizures, in addition to exaggerated common side effects such as persistent vomiting, marked tachycardia, and agitation. In case of a known or suspected overdose of Doxofyl, seek immediate medical attention or contact a poison control center or emergency services; do not attempt to manage a suspected overdose at home. There is no specific antidote for Doxofyl overdose; treatment in hospital is supportive, with cardiovascular monitoring and symptomatic management of arrhythmia or seizures. Treatment with Doxofyl should be discontinued and only resumed at a lower dose, if at all, once toxicity has resolved and under medical supervision.

Store Doxofyl at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Renal impairment

Use Doxofyl with caution in patients with renal impairment; monitoring is advised as elimination of the drug and its metabolites may be affected.

Hepatic impairment

Doxofyl is extensively metabolized by the liver, and hepatic impairment can significantly reduce its clearance. A reduced dose (e.g. 200 mg instead of 400 mg per dose) and closer monitoring are recommended in these patients.

Elderly

Elderly patients often have reduced hepatic clearance of Doxofyl and are generally started on the lower 200 mg dose two to three times daily.

Children

See Pediatric Uses and Dosage and Administration for age-appropriate dosing of Doxofyl in children.

Effect on driving/operating machinery

Doxofyl is not reported to impair alertness or the ability to drive or operate machinery at recommended doses, but individual response can vary.

Doxofyl is generally used as a long-term, ongoing maintenance therapy for chronic asthma and COPD, alongside other prescribed respiratory medicines, rather than as a short course. The duration of treatment with Doxofyl should be determined by the prescribing physician based on disease control, and treatment should not be stopped or altered without medical advice even if symptoms improve.

Doxophylline is classified as a Xanthine derivative / Bronchodilator, structurally related to theophylline but with reduced affinity for adenosine receptors.

Doxophylline relaxes bronchial smooth muscle mainly through non-selective inhibition of phosphodiesterase enzymes, which increases intracellular cyclic AMP in airway smooth muscle cells and produces bronchodilation. Because Doxophylline has low affinity for adenosine receptors compared with theophylline, it is thought to produce less adenosine-receptor-mediated cardiac stimulation and CNS excitation at therapeutic doses.

Use of Doxofyl in children should follow age- and weight-based dosing under medical guidance:

• Children under 6 years: safety and efficacy of Doxofyl have not been well established; use is generally not recommended unless specifically directed by a pediatrician.
• Children 6-12 years: weight-based syrup dosing, typically 6-9 mg/kg body weight twice daily (see Dosage and Administration).
• Children over 12 years: dosing similar to adults, adjusted for body weight, using tablet or syrup formulations.

Sustained-release tablets of Doxofyl are intended for adult use and are generally not used in children. Parents and caregivers should not exceed the recommended dose of Doxofyl and should consult a pediatrician regularly to monitor growth and treatment response.