• NOTE: This page is intended to be a quick reference for properties of methylxanthines. It is NOT a comprehensive review of this medication. Other drug interactions, side effects, precautions, and contraindications may exist for each drug.


Drug Dosage form Dosage Lab monitoring Generic/Price Other Class/Mechanism of Action Indications
Side Effects
Drug Interactions Precautions/

Extended-release tablet
  • 100mg
  • 200mg
  • 300mg
  • 400mg
  • 450mg
  • 600mg

Extended-release capsule (Theo-24®)
  • 100mg
  • 200mg
  • 300mg
  • 400mg

Standard-release tablet (Theolair®)
  • 125mg
  • 250mg
General points
  • Theophylline extended-release capsules and tablets are typically dosed once a day, but twice a day dosing may be required in some patients
  • Standard-release theophylline (Theolair®) is dosed every 12 hours
  • Theophylline distributes poorly into fat. Dosing should be based on ideal body weight.
  • Theophylline dosing is adjusted based on theophylline blood levels

Dosing charts
Dosing charts for the different theophylline products are available in the PIs
  • Theophylline pharmacokinetics vary widely between individuals
  • Half-life (1 - 4 years): average 3.4hr (range 1 - 6hr)
  • Half-life (6 - 17 years): average 3.7hr (range 1.5 - 6hr)
  • Half-life (16 - 60 years): average 8.7hr (range 6 - 13hr)
  • Half-life (≥ 60 years): average 9.8hr (range 1.6 - 18hr)
  • Time to steady state (adults): average 40hr (range 30 - 65hr)
  • Time to steady state (1 - 17 years): range 5 - 40hr
  • Reference: Theo-24® PI and Qwest diagnostics®

Normal levels (Peak concentrations)
  • ≤ 5 months: 5 - 10mg/L
  • > 5 months and adults: 10 - 20mg/L
  • Reference: Qwest diagnostics®

Lab monitoring (children and adults)
  • Dose adjustments are based on peak levels
  • For most patients, steady state will be reached after 3 days of dosing
  • Peak levels (Theo-24®): 12 hours after a dose at steady state
  • Peak levels (Extended-release tab): 12 hours after an evening dose or 9 hours after a morning dose at steady state
  • Peak levels (Immediate-release tab): 1-2 hours after a dose at steady state

Dose adjustments
  • Dose adjustments are based on peak levels
  • A table in the PI gives recommendations
  • Theophylline PI
  • In patients with stable levels, levels should be checked at 6 month intervals in rapidly growing children, and yearly in adults
Extended-release capsule (Theo-24®)

Extended-release tablet

Immediate-release tablet (Theolair®)
  • High fat meals increase absorption. Patients taking high doses (ex. ≥ 900mg), should not take dose less than 1 hour before high-fat meal.
  • Once daily regimens - take dose in morning

Extended-release tablets®
  • Do not crush or chew tablets
  • Scored tablets may be split
  • Tablet shell may be seen in stool. This is normal.
  • Food increases absorption. Tablets should be taken consistently with or without food.
  • Transfer from immediate-release to extended-release tablet can be done on a mg-to-mg basis

Immediate-release tablets®
  • Food does not affect absorption
  • Methylxanthine - theophylline is a methylxanthine. Theophylline promotes bronchial smooth muscle relaxation and suppresses airway hyperresponsiveness to stimuli.
  • Theophylline is indicated for the treatment of the symptoms and reversible airflow obstruction associated with chronic asthma and other chronic lung diseases, e.g., emphysema and chronic bronchitis
  • Incidence of side effects not well-defined
  • Nausea and vomiting
  • Headache
  • Insomnia
  • Behavior changes
  • Irritability
  • Tremor
  • Transient increase in urination
  • Lab effects: May increase blood glucose levels, uric acid levels, triglycerides, total cholesterol, HDL, and cortisol levels. May decrease thyroid levels.

Signs of Theophylline toxicity
  • Nausea and vomiting
  • Rapid heart rate
  • Heart arrhythmias
  • Anxiety/tremor
  • Seizures
  • Low potassium
  • Elevated blood sugar
  • Theophylline has a large number of documented drug interactions
  • A table in the PI (Table II) lists known drug interactions
  • Another table (Table III) lists drugs that are known to not interact with theophylline
  • Theophylline PI (under PRECAUTIONS)

  • CYP1A2 inducers and inhibitors - theophylline is a CYP1A2 sensitive substrate
  • Active peptic ulcer disease - use caution, may worsen
  • Seizures - use caution, may worsen
  • Heart arrhythmias - use caution, may worsen
  • Children < 3 months of age - theophylline clearance is altered. Requires frequent monitoring.
  • Elderly - use caution. Theophylline levels may increase.
  • Heart failure - use caution. Theophylline levels may increase.
  • Fever and infection - use caution. Theophylline levels may increase.
  • Low thyroid - use caution. Theophylline levels may increase.
  • Cessation of smoking - use caution. Theophylline levels may increase. Smoking induces CYP1A2 and lowers theophylline levels.
  • Liver disease - theophylline clearance is reduced. Careful monitoring of levels required.
  • Kidney disease - Children ≥ 3 months of age and adults: no dose adjustment necessary


    • $ = 0 - $50
    • $$ = $51 - $100
    • $$$ = $101 - $150
    • $$$$ = > $151

    • Pricing based on one month of therapy at standard dosing in an adult
    • Pricing based on survey of GoodRX.com® [accessed 3/2015]
    • Pricing may vary by region and availability

  • References:
  • 1 - Manufacturer's Package Insert