Generic Theophylline

Buy Generic Theophylline () without prescription in Canada

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Theophylline is a bronchodilator belonging to the xanthine class, used to prevent and treat wheezing, shortness of breath, and chest tightness caused by asthma, chronic bronchitis, emphysema, and other chronic obstructive pulmonary diseases. It works by relaxing the smooth muscles of the airways and decreasing the responsiveness of the lungs to irritants. Theophylline is not a first-line therapy for acute asthma attacks but is an effective maintenance treatment for chronic respiratory conditions, especially when symptoms are not fully controlled by inhaled medications. The 400 mg dose refers to extended-release formulations that allow for once-daily dosing, providing steady therapeutic levels over 24 hours.

Usual adult dose: The recommended starting dose for extended-release theophylline is 400 mg taken orally once daily, preferably in the evening with food to minimize stomach upset. After 3-5 days, serum theophylline levels should be measured to ensure they are within the therapeutic range of 55-110 µmol/L (10-20 µg/mL). The dose may be adjusted upward or downward in small increments based on clinical response and blood levels, not exceeding 600 mg daily without careful monitoring. For patients with liver disease, heart failure, or those taking certain interacting medications, lower initial doses (e.g., 200 mg daily) are recommended. The tablet should be swallowed whole with a glass of water and must not be crushed or chewed.

Dosage form: Extended-release (controlled-release) oral tablet, 400 mg. Theophylline is also available in other strengths (100 mg, 200 mg, 300 mg, and 600 mg) and as an oral solution.

Onset of action: Bronchodilation begins within hours of the first dose, but the full therapeutic effect develops over 3-5 days of continuous once-daily administration. The peak effect of the extended-release formulation occurs 6-10 hours after dosing, providing overnight and early-morning protection against respiratory symptoms.

Duration of action: Approximately 24 hours, allowing once-daily maintenance dosing. The elimination half-life of theophylline varies widely (3-12 hours in adults), so the extended-release design is essential for maintaining consistent blood levels.

Alcohol recommendation: Alcohol consumption should be strictly avoided during treatment with Theophylline. Alcohol can disrupt the extended-release mechanism, causing "dose dumping" and a rapid, potentially dangerous rise in blood levels, increasing the risk of toxicity.

Most common side effects: Nausea, vomiting, headache, insomnia, nervousness, irritability, diarrhoea, and palpitations. These are often dose-related and may improve with continued therapy or dose reduction. More serious signs of toxicity include severe nausea, persistent vomiting, rapid or irregular heartbeat, confusion, or seizures, which require immediate medical attention.

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General Information about Theophylline

• INN (International Nonproprietary Name): Theophylline (anhydrous)
• Brand names available in Canada: Uniphyl Cr® (Bausch Health, Canada Inc.) is the primary brand for extended-release theophylline 400 mg. Generic versions include Apo-Theo LA (Apotex Inc.), Novo-Theophyl SR (Teva Canada Limited), PMS-Theophylline (Pharmascience Inc.), and others. Theophylline is also available in combination products (e.g., with ephedrine) and as an oral solution (Theolair®).
• ATC code: R03DA04 (theophylline; xanthines)
• Dosage forms and strengths: Extended-release (controlled-release) tablets: 100 mg, 200 mg, 300 mg, 400 mg, and 600 mg. Oral solution: 80 mg/15 mL (5.33 mg/mL).
• Manufacturers in Canada: Bausch Health, Canada Inc. (Uniphyl Cr), Apotex Inc., Teva Canada Limited, Pharmascience Inc., and other generic manufacturers.
• Registration status in Canada: Approved by Health Canada. Marketed (DINs: 00872605 for Uniphyl Cr 400 mg, plus generic equivalents).
• OTC / Rx classification: Prescription only (Rx). Schedule I drug under the Controlled Drugs and Substances Act. A valid prescription from a licensed Canadian healthcare professional is required.

Mechanism of Action and Pharmacology

Theophylline is a methylxanthine derivative that produces bronchodilation, increases diaphragmatic contractility, and has mild anti-inflammatory and immunomodulatory effects. Its primary mechanism of action is non-selective inhibition of phosphodiesterase (PDE) isoenzymes, particularly PDE III and IV, which leads to an increase in intracellular cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). This relaxes bronchial smooth muscle and reduces the release of inflammatory mediators. Theophylline also antagonizes adenosine A1 and A2 receptors in the lung, preventing bronchoconstriction and the release of histamine from mast cells. Additionally, it enhances mucociliary clearance and stimulates the respiratory centre, which can improve breathing drive. Theophylline is not a first-line agent for acute asthma exacerbations but is effective for long-term control of persistent symptoms.

After oral administration, theophylline is rapidly and completely absorbed from the gastrointestinal tract. The extended-release formulation is designed to release the drug slowly, with peak plasma concentrations occurring approximately 6-10 hours after a dose taken with food. The absolute bioavailability is near 100%. Theophylline is extensively metabolized in the liver, primarily by cytochrome P450 1A2 (CYP1A2), with a minor contribution from CYP2E1 and CYP3A4. The elimination half-life is highly variable: 3-12 hours in adults, prolonged in neonates, elderly, and patients with liver disease, heart failure, or acute pulmonary oedema. Smoking and marijuana use significantly induce CYP1A2 and can decrease the half-life by 50-70%, requiring higher doses. Conversely, ciprofloxacin, cimetidine, and other CYP1A2 inhibitors can dramatically increase theophylline levels. Because of the narrow therapeutic window, serum concentration monitoring is essential, with a target range of 55-110 µmol/L (10-20 µg/mL). The protein binding is about 40-60%, and the volume of distribution is approximately 0.5 L/kg. Theophylline is excreted mainly in the urine as metabolites (1,3-dimethyluric acid, 1-methyluric acid, and 3-methylxanthine), with only about 10% eliminated unchanged.

Indications

• Maintenance therapy for chronic stable asthma and for the prevention of nocturnal asthma symptoms.
• Maintenance therapy for chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema, when symptoms are not adequately controlled by inhaled bronchodilators and corticosteroids.
• Not indicated for the treatment of acute asthma attacks or status asthmaticus; rapid-acting inhaled beta-agonists should be used for rescue therapy. Theophylline may be used as an adjunct to inhaled therapies for patients with persistent symptoms.

Important Warnings and Precautions

At-risk groups

• Elderly: Clearance is reduced; lower initial doses and careful serum level monitoring are essential because toxicity can occur at concentrations only slightly above the therapeutic range.
• Pregnancy: Theophylline crosses the placenta. It should be used during pregnancy only if the potential benefit justifies the risk to the foetus. Neonates may experience jitteriness, vomiting, and tachycardia if maternal levels are high. Category C.
• Breastfeeding: Theophylline passes into breast milk; breastfed infants may become irritable. Nursing mothers should either discontinue the drug or breastfeeding, depending on the importance of therapy.
• Paediatric: Children under 45 kg require weight-based dosing and strict serum level monitoring. The safety and efficacy of once-daily Uniphyl Cr in children less than 12 years of age have not been fully established; alternative paediatric formulations are available.
• Hepatic impairment: Metabolism is significantly reduced; start with 200 mg daily and titrate cautiously under serum level guidance.
• Heart failure: Theophylline clearance is decreased; reduced doses are required.
• Smokers: Tobacco smoking induces CYP1A2 and markedly increases clearance; higher doses may be needed. Conversely, sudden smoking cessation can cause a rapid rise in serum theophylline and toxicity.
• Viral infections and febrile illness: Clearance may be transiently decreased; dose reduction may be necessary during acute illness.
• Seizure disorders: Theophylline may lower the seizure threshold; use with extreme caution and only if on adequate anticonvulsant therapy.
• Peptic ulcer disease: Theophylline increases gastric acid secretion and may aggravate ulcers; contraindicated in active disease.
• Cardiac arrhythmias: Theophylline can cause or worsen tachyarrhythmias; caution in patients with unstable cardiac conditions.

Driving and alcohol

Theophylline may cause dizziness, nervousness, insomnia, and tremor, which can impair the ability to drive or operate machinery. Patients should assess their individual response before engaging in such activities. Alcohol must be avoided entirely because it can disrupt the controlled-release mechanism of Uniphyl Cr, leading to dose-dumping and acute toxicity, which can be fatal. Patients should not consume any alcoholic beverages during treatment.

Dosage Instructions

• Initial dose: For adults and adolescents weighing > 45 kg not currently receiving theophylline, start with 400 mg once daily in the evening with food. For patients weighing ≤ 45 kg, elderly, or those with risk factors for reduced clearance (liver disease, heart failure, concomitant CYP1A2 inhibitors), begin with 200 mg once daily.
• Titration: After 3-5 days, measure serum theophylline concentration just before the next dose (trough level). Target range: 55-110 µmol/L (10-20 µg/mL). If the level is subtherapeutic and tolerated, increase the dose by 100-200 mg/day every 3-5 days. If the level exceeds the therapeutic range or side effects occur, reduce the dose proportionally.
• Maximum dose: Without serum level monitoring, do not exceed 400 mg daily. With monitoring, doses up to 600 mg daily may be prescribed, though some patients require up to 900 mg daily. Higher doses must be justified by serum concentrations.
• Administration: Swallow the tablet whole with a glass of water; do not crush, chew, or break the tablet. Administer consistently with the evening meal; food enhances the reliability of absorption and reduces gastric irritation.
• Special populations: Children under 12 years of age and infants - use only under specialist guidance with weight-adjusted immediate-release or paediatric sustained-release products; once-daily Uniphyl Cr is not recommended in this age group.

Side Effects and Contraindications

• Common, usually dose-related side effects: Nausea, vomiting, epigastric pain, diarrhoea, headache, insomnia, nervousness, irritability, tremor, palpitations, and tachycardia. These often respond to dose reduction.
• Serious side effects (usually associated with serum levels > 110 µmol/L or rapid rise): Severe tachycardia, ventricular arrhythmias, cardiac arrest, convulsions (which may occur without warning and can be resistant to treatment), gastrointestinal haemorrhage, hyperglycaemia, hypokalaemia, and rhabdomyolysis. Toxicity can be fatal.
• Contraindications: Hypersensitivity to theophylline, other xanthines, or any excipient. Active peptic ulcer disease. Uncontrolled seizure disorder (unless on effective anticonvulsant therapy). Concomitant use with fluvoxamine. Breastfeeding (relative).

Drug Interactions

• Major inhibitors of theophylline metabolism (increase levels, toxicity risk): Fluvoxamine (absolute contraindication), ciprofloxacin and other fluoroquinolones, cimetidine, erythromycin, clarithromycin, verapamil, disulfiram, allopurinol, ticlopidine, and severe hepatic impairment. Doses must be reduced and levels monitored closely.
• Inducers of theophylline metabolism (decrease levels, loss of efficacy): Tobacco smoking, marijuana smoking, phenytoin, phenobarbital, carbamazepine, rifampin, ritonavir, and St. John's wort. Higher doses may be needed; abrupt cessation of the inducer can cause toxicity.
• Pharmacodynamic interactions: Additive CNS stimulation with sympathomimetics (e.g., salbutamol, pseudoephedrine) can increase nervousness and tremor. Additive hypokalaemia with corticosteroids, loop diuretics. Theophylline may antagonize the effects of adenosine and benzodiazepines. Lithium clearance may be increased, reducing serum lithium levels. Beta-blockers (including eye drops) can antagonize theophylline bronchodilation.
• Food and beverage: A high-fat meal can increase the rate of absorption of Uniphyl Cr and potentially cause toxicity; consistent administration with food (preferably low-fat) is recommended. Caffeine shares similar pharmacologic actions and may increase side effects; intake should be moderated.

Practical Advice

• Take Theophylline once daily in the evening, with food, to achieve the best nocturnal coverage and reduce stomach upset.
• Do not crush, chew, or halve the tablet; the controlled-release matrix ensures gradual drug delivery.
• Store at room temperature (15-30 °C) in a dry place, tightly closed, and out of reach of children.
• Adhere to the prescribed dosage schedule; never double a missed dose. If a dose is missed, take it as soon as remembered unless it is close to the time for the next dose.
• Regularly attend blood tests for serum theophylline levels, especially after starting therapy, dose changes, new medications, or changes in health status (e.g., viral infection, heart failure, smoking cessation).
• Inform every healthcare provider that you are taking theophylline, including dentists and pharmacists, to avoid potentially dangerous drug interactions.
• Seek immediate medical attention if signs of toxicity appear: persistent nausea, vomiting, fast or irregular heartbeat, severe headache, confusion, or convulsions.
• Keep a consistent diet and avoid binge drinking or heavy alcohol use; abstain from alcohol completely.

Alternative Medications

• Inhaled bronchodilators: Long-acting beta-agonists (LABAs) such as salmeterol and formoterol, and long-acting anticholinergics (LAMAs) such as tiotropium, are first-line maintenance therapies for asthma and COPD, with a superior safety profile.
• Inhaled corticosteroids: Beclomethasone, fluticasone, budesonide form the cornerstone of anti-inflammatory management in persistent asthma.
• Leukotriene receptor antagonists: Montelukast and zafirlukast are oral agents used for mild persistent asthma or as add-on therapy, without the narrow therapeutic window of theophylline.
• Combination products: Fixed-dose inhalers (ICS/LABA) provide convenient dual-action therapy (e.g., fluticasone/salmeterol, budesonide/formoterol).
• Other oral options: Roflumilast (a PDE-4 inhibitor) is available for severe COPD with chronic bronchitis. Oral steroids are reserved for exacerbations.
• Immediate-release theophylline: In patients requiring a flexible, shorter-acting theophylline preparation for acute titration, immediate-release tablets or elixir are available, though Uniphyl Cr is preferred for maintenance.

Clinical Efficacy

Theophylline has been used as a bronchodilator for decades, and its efficacy in improving lung function and reducing symptoms in chronic asthma and COPD is well established. When administered as controlled-release theophylline (Uniphyl Cr) once daily in the evening, it provides effective 24-hour control of airway obstruction, particularly blunting the early-morning dip in peak expiratory flow (PEF) that often accompanies nocturnal asthma. In multiple studies, theophylline improved FEV1 by 10-15% from baseline and reduced the need for rescue inhalers. Addition of theophylline to a regimen of inhaled corticosteroids and LABAs has been shown to provide further symptomatic improvement in difficult-to-control asthma. However, theophylline has a narrow therapeutic index, and its use has declined in favour of safer inhaled therapies. In COPD, theophylline has modest benefits in improving dynamic hyperinflation and exercise tolerance, and it serves as an alternative or add-on when inhaled bronchodilators are insufficient. The clinical benefit is closely linked to achieving and maintaining serum levels within the 55-110 µmol/L range; subtherapeutic levels yield little effect, while toxicity emerges quickly above 110 µmol/L.

Important:

Theophylline is a prescription medication with a narrow margin between therapeutic effect and serious toxicity. It must be used only under ongoing medical supervision with regular monitoring of serum theophylline concentrations. Never adjust the dose without consulting a healthcare professional. Many common drugs, illnesses, and lifestyle factors can drastically alter theophylline blood levels, so inform your doctor of all medications, including over-the-counter products and herbal remedies. If symptoms such as persistent nausea, vomiting, rapid heartbeat, restlessness, or convulsions occur, stop taking the medication and seek emergency medical attention immediately. This information is not a substitute for professional medical advice, diagnosis, or treatment.

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