Theophylline

Indications
Oral
Acute bronchospasm
Adult: As conventional tablet: 5 mg/kg every 6-8 hr.
Child: As conventional tablet: 5 mg/kg every 4-6 hr.
Hepatic impairment: Dose adjustment needed.
Oral
Chronic bronchospasm
Adult: As conventional dosage form: 300-1000 mg in divided doses, every 6-8 hr daily. As modified-release preparations: 175-500 mg every 12 hr. Rate of absorption of modified released preparations varies for different brands.
Child: <2 yr: Not recommended; 2-6 yr: ¼ the adult dose; 20-35 kg (about 6-12 yr old): ½ the adult dose. Rate of absorption of modified released preparations varies for different brands.
Hepatic impairment: Dose adjustment needed.
Oral
Apnoea in infants
Child: Initial dose in neonates: ≤24 days: 1 mg/kg every 12 hr; >24 days: 1.5 mg/kg every 12 hr. Full-term infants: initial daily dosage calculated based on formula, given in 3-4 divided doses: daily dose (mg/kg) = (0.2 X age in wk) + 5.0. If loading dose is needed, 5 mg/kg (or in those already on theophylline, 1 mg/kg for each 2 mcg/ml increase in serum-theophylline concentration).
Intravenous
Severe bronchospasm
Adult: Patients who are not taking theophylline or other xanthine medication: 4-5 mg/kg as loading dose by IV infusion over 20-30 minutes followed by maintenance: 0.4 mg/kg/hr.
Child: Patients who are not taking theophylline or other xanthine medication: 4-5 mg/kg as loading dose by IV infusion over 20-30 minutes, followed by maintenance dose: 1-9 yr: 0.8 mg/kg/hr; >9 yr: 0.6-0.7 mg/kg/hr.
Hepatic impairment: Dose adjustment needed.

Special Populations: Reduce dose in patients with cor pulmonale, heart failure, liver disease and in the elderly. Increase maintenance dose for smokers.
Contraindications
Hypersensitivity to xanthine derivatives, porphyria.
Warnings / Precautions
Admin IV inj very slowly to avoid direct stimulation of the CNS and CVS. Cardiac failure, hypertension, epilepsy, hyperthyroidism, history of peptic ulcer disease, renal or hepatic dysfunction, glaucoma, DM, severe hypoxaemia, chronic alcoholism, acute febrile illness. On influenza immunization or active influenza infection, COPD and cor pulmonale. Smokers may need higher dose. Pregnancy, lactation, children and elderly.
Adverse Reactions
Nausea, vomiting, abdominal pain, diarrhoea, headache, insomnia, dizziness, anxiety, restlessness, tremor, palpitations.
Potentially Fatal: Convulsions, cardiac arrhythmias, hypotension and sudden death after too rapid IV inj.
Overdose Reactions
Nausea, vomiting, diarrhoea, agitation, tremor, hypertonicity, hyperventilation, diuresis and repeated vomiting (sometimes haematemesis), cardiac arrhythmias including tachycardia, hypotension, electrolyte disturbances including hypokalaemia, hyperglycaemia, hypophosphataemia, hypercalcaemia, metabolic acidosis, respiratory alkalosis and convulsions. Other reported effects include dementia, toxic psychosis, symptoms of acute pancreatitis, rhabdomyolysis with renal failure and acute compartment syndrome. Empty stomach by lavage if within 2 hr of overdose, with repeated oral doses of activated charcoal and osmotic laxative, especially if modified-release tablets taken. Symptomatic and supportive treatment with monitoring of serum theophylline concentrations. Non-selective βblockers to be used in non-asthmatic patient for tachycardia, IV diazepam or a barbiturate to control convulsions, disopyramide may be used in patients with both ventricular arrhythmias and convulsions. In severe cases, general anaesthesia and neuromuscular blockade with ventilation may be needed. Charcoal haemoperfusion or haemodialysis may be helpful especially in CHF or liver disease.
Drug Interactions
Other xanthines. Theophylline clearance reduced by high dose allopurinol, some antiarrhythmics, cimetidine, disulfiram, propranolol, methotrexate, aciclovir, mexiletine, pentoxifylline, tacrine, ticlopidine, fluvoxamine, interferon-α, macrolide antibiotics, quinolones, oral contraceptives, thiabendazole and viloxazine. Theophylline clearance increased by phenytoin, anticonvulsants, ritonavir, rifampicin, sulfinpyrazone, aminoglutethimide, barbiturates, ipriflavone, cigarette smoking. Concurrent use decreased lithium, alprazolam levels. Increased risk of arrhythmias with ephedrine, sympathomimetic, general anaesthetics. Increased heart rate with tadalafil.
See Below for More theophylline Drug Interactions
Lab Interactions
May cause false positive elevations of serum uric acid (by Bittner or colorimetric method) and increase in urinary catecholamines. Serum theophylline concentrations may be falsely elevated by furosemide, sulfathiazole, phenylbutazone, probenecid, theobromine, caffeine-containing beverages, chocolate and paracetamol if measured by spectrophotometric methods. Theophylline can inhibit the effects of adenosine infusions used in conjunction with radionuclide myocardial imaging, if not withheld 12-24 hr before procedure; reduces the diagnostic accuracy of myocardial imaging using dipyridamole.
Food Interactions
St John's wort may increase theophylline levels. Avoiding giving enteral feed for 1 hour before or after theophylline to prevent reduction in theophylline levels.
Mechanism of Actions
Theophylline competitively blocks phosphodiesterase which increases cAMP tissue concentrations causing bronchodilatation, diuresis, CNS and cardiac stimulation, and gastric acid secretion.
Absorption: Rapid and completely absorbed following oral and rectal (enemas) administration, slow after rectal (suppositories) and IM administration. Food delays rate but not extent of absorption. Peak serum concentrations: 1-2 hr (liquid, capsules or uncoated tablets); 4 hr (modified-release preparations).
Distribution: Rapidly distributed throughout extracellular fluids and body tissues. Crosses the placenta and enters breast milk. Protein binding: 40%.
Metabolism: Hepatic metabolism via cytochrome P450 isoenzyme CYP1A2, CYP2E1 and CYP3A3. Serum half-life: 6-12 hr (healthy, non-smoking asthmatic adult); 1-5 hr (children); 4-5 hr (cigarette smokers); 10-45 hr (neonates and premature infants).
Excretion: Via urine as metabolites and unchanged drug; small amount via faeces as unchanged drug
Administration
May be taken with or without food. (May be taken w/ meals to reduce GI discomfort. Some individual prep must be taken w/ meals or on an empty stomach. Refer to monographs for individual formulations.)
ATC Classification
R03DA04 - theophylline ; Belongs to the class of xanthines. Used in the systemic treatment of obstructive airway diseases.
Available As
  • Theophylline 100 mg
  • Theophylline 104 mg
  • Theophylline 125 mg
  • Theophylline 130 mg
  • Theophylline 138 mg
  • Theophylline 14 mg
  • Theophylline 150 mg
  • Theophylline 198 mg
  • Theophylline 200 mg
  • Theophylline 23 mg
  • Theophylline 25 mg
  • Theophylline 25.3 mg
  • Theophylline 25.30 mg
  • Theophylline 250 mg
  • Theophylline 27 mg
  • Theophylline 30 mg
  • Theophylline 300 mg
  • Theophylline 32.5 mg
  • Theophylline 35 mg
  • Theophylline 400 mg
  • Theophylline 50 mg
  • Theophylline 50.6 mg
  • Theophylline 600 mg
  • Theophylline 65 mg
  • Theophylline 69 mg
  • Theophylline 77 mg
  • Theophylline 80 mg
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