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Theophylline

Medication xanthine bronchodilator respiratory
Aka: Nuelin, aminophylline
Brands seen in Singapore: Nuelin-SR, Nuelin Syrup, Apo-Theo LA, Theolin SR
Not medical advice. Check with your doctor or pharmacist before you start, stop or change the timing of anything you take.
How to use
What it’s for
HealthHub: opens the airways in asthma and lung disease
When to take
SG label: sustained-release tablets every twelve hours
Take with
HealthHub: with or without food · less caffeine alongside
Pros & cons
Pros
  • HealthHub: relaxes the muscles around the airways
  • SG label: relief and prevention of bronchospasm
  • Tablets and syrup — no inhaler technique involved
Cons
  • Toxic effects can occur even at normal blood levels
  • HealthHub: nausea, palpitations, headache, poor sleep
  • US label: many drugs change how fast it is cleared
Sources
  1. HSA — Listing of Registered Therapeutic Products (data.gov.sg open dataset, 5,511 rows, cached in full and filtered locally) · read 2026-08-27
    what it says
    “All 9 rows read 'Prescription Only' — NUELIN-SR 125 and 250 TABLET · NUELIN SYRUP 80 mg/15 ml · APO-THEO LA TABLET 100/200/300 mg · THEOLIN SR TABLET 250 mg · AMINOPHYLLINE INJECTION”
  2. National Drug Formulary (SG, MOH) — NUELIN-SR 250 TABLET [SIN10679P], indications and dosage, last updated 28 Jul 2026 · read 2026-08-27
    what it says
    “For the relief and prophylaxis of reversible bronchospasm associated with bronchial asthma, bronchitis, emphysema and related conditions … ADULTS: 200 to 300 mg (one tablet) every twelve hours … Nuelin SR tablets should be taken every twelve hours”
  3. National Drug Formulary (SG, MOH) — NUELIN-SR 250 TABLET [SIN10679P], serum level and monitoring text · read 2026-08-27
    what it says
    “Desirable therapeutic levels are considered to be between 10–20 mcg/mL … Higher levels may produce toxic effects. Toxic effects may also occur at therapeutic levels … Monitoring is particularly recommended when dose levels exceed 1 g daily in adults”
  4. HealthHub (MOH Singapore / Pharmaceutical Society of Singapore) — Theophylline medication leaflet · read 2026-08-27
    what it says
    “Theophylline opens the airways in your lungs, making it easier to breathe. It works by relaxing the smooth muscles around your airways that can tighten in asthma, COPD, and other lung conditions”
  5. HealthHub — Theophylline leaflet: common side effects · read 2026-08-27
    what it says
    “Nausea and stomach upset (this can be reduced by taking theophylline after food). Fast heartbeat and palpitations. Headache. Flushing. Difficulty in sleeping. Shakiness or feeling anxious”
  6. HealthHub — Theophylline leaflet: precautions before starting · read 2026-08-27
    what it says
    “You have the following medical conditions: Seizures or fits. Stomach ulcers. Heart problems with fast or irregular heartbeat. Thyroid problems. Liver problems … You are a smoker and want to stop smoking”
  7. HealthHub — Theophylline leaflet: food and medicines to avoid · read 2026-08-27
    what it says
    “You should cut down on your intake of caffeine as it has similar effects to theophylline. Caffeine is commonly found in tea, coffee, chocolates, and cola … Inform your doctor if you smoke or plan to quit smoking”
  8. US FDA label — Theophylline (Chartwell RX, LLC), DOSAGE AND ADMINISTRATION, via openFDA (SPL effective 6 Feb 2026) · read 2026-08-27
    what it says
    “In adolescents 16 years and adults, including the elderly, the final theophylline dose should not exceed 400 mg/day in the presence of risk factors for reduced theophylline clearance … or if it is not feasible to monitor serum theophylline concentrations”
  9. US FDA label — Theophylline (Chartwell RX, LLC), WARNINGS: concurrent illness and conditions that reduce clearance, via openFDA · read 2026-08-27
    what it says
    “should be used with extreme caution in patients with … Active peptic ulcer disease. Seizure disorders. Cardiac arrhythmias … If the total daily dose is not appropriately reduced … severe and potentially fatal theophylline toxicity can occur”
  10. US FDA label — Theophylline (Chartwell RX, LLC), PRECAUTIONS: Drug Interactions and Table II, via openFDA · read 2026-08-27
    what it says
    “Theophylline interacts with a wide variety of drugs … Cimetidine Decreases theophylline clearance by inhibiting cytochrome P450 1A2 70% increase. Ciprofloxacin Similar to cimetidine … Carbamazepine … 30% decrease”
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Updated 2026-08-29. Every line above traces to a numbered source. Kozen-X is not a medical device and does not give medical advice. It lists what published sources have written down — nothing more. A pair not listed is unrecorded, not cleared. Before you start, stop or re-time anything, talk to your doctor or pharmacist.