Comprehensive medication guide to Theo-24 XR including estimated pricing, availability information, side effects, and how to find it in stock at your local pharmacy.
Estimated Insurance Pricing
$0–$15 copay per month; covered as a Tier 1 preferred generic on most commercial insurance plans and Medicare Part D. No prior authorization typically required for standard doses.
Estimated Cash Pricing
$10–$40 per month for generic theophylline ER tablets (30-day supply) at retail; as low as $4–$15 with GoodRx, SingleCare, or RxSaver coupons. Walmart's $4 generic list may include theophylline at select locations.
Medfinder Findability Score
40/100
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Theo-24 XR is the brand name for theophylline anhydrous extended-release capsules designed for once-daily dosing. It belongs to the methylxanthine class of bronchodilators and is used for the long-term management of chronic asthma and COPD (emphysema and chronic bronchitis). The drug has been in use since the 1950s and remains an important option for patients who need an affordable oral bronchodilator.
The original Theo-24 brand was manufactured by Endo Pharmaceuticals in 100 mg, 200 mg, 300 mg, and 400 mg capsules. While the brand name has been largely discontinued, generic theophylline extended-release capsules and tablets remain available from manufacturers including Glenmark, Rhodes Pharmaceuticals, and Alembic.
Theophylline is not a first-line treatment per current clinical guidelines — inhaled therapies are preferred for most patients. However, it retains clinical value for patients who cannot use inhalers effectively, face significant cost barriers to inhaled therapies, or have not achieved adequate control with inhaled agents alone.
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Theo-24 XR (theophylline) is a methylxanthine bronchodilator that works through multiple mechanisms. Its primary action is inhibiting phosphodiesterase enzymes — specifically PDE III and PDE IV. This prevents the breakdown of cyclic AMP (cAMP) in airway smooth muscle cells. When cAMP levels remain elevated, the muscle cells relax and airway passages widen, making breathing easier.
Theophylline also acts as an adenosine receptor antagonist — the same mechanism as caffeine (its chemical relative). Blocking adenosine receptors in the lungs reduces bronchoconstriction signaling. Additionally, theophylline increases the force of diaphragm muscle contractions through an adenosine-mediated calcium channel mechanism, improving breathing efficiency in COPD patients with respiratory muscle fatigue.
The extended-release formulation releases theophylline gradually over 24 hours, maintaining steady blood levels and providing continuous bronchodilation. Because theophylline has a narrow therapeutic window (target serum levels of 5–15 mcg/mL), regular blood level monitoring is required throughout therapy to ensure efficacy and prevent toxicity.
100 mg — extended-release capsule
Starting dose for some patients; once daily. Most commonly available strength.
200 mg — extended-release capsule
Commonly used maintenance dose; once daily. Generally available.
300 mg — extended-release capsule or tablet
Maintenance dose for moderate requirements; once daily. Intermittent availability.
400 mg — extended-release capsule or tablet
Higher maintenance dose; once daily. Most affected by 2025-2026 shortage. On back order at multiple manufacturers.
Theo-24 XR (and generic theophylline ER) has been experiencing intermittent supply disruptions since 2022, with an active ASHP shortage listing since August 2023. As of early 2026, availability depends heavily on the strength needed. The 400 mg strength is the most difficult to find — both Glenmark and Rhodes have it on back order with no estimated release date, and Glenmark recalled multiple batches in August 2025 due to dissolution test failures.
Lower strengths (100 mg and 200 mg) are generally more available, though spot shortages occur. Availability varies significantly by region and pharmacy type — independent pharmacies and mail-order pharmacies often have stock when chain pharmacies don't.
If you're having trouble finding Theo-24 XR, medfinder calls pharmacies near you to check which ones can fill your prescription — saving you hours of calling around. Start your refill search 7–10 days before you run out to give yourself time to locate stock.
Because Theo-24 XR (theophylline) is not a controlled substance, it can be prescribed by any licensed healthcare provider in the United States. There are no special DEA registration requirements or prescribing restrictions. Any provider with prescribing authority can write for theophylline extended release.
Pulmonologists — Lung specialists with the most expertise in theophylline management and monitoring.
Primary care physicians (PCPs) — Family medicine doctors and internists who commonly manage stable asthma and COPD patients on theophylline.
Allergists and immunologists — Specialists in allergic asthma who may prescribe theophylline as adjunct therapy.
Nurse practitioners (NPs) and physician assistants (PAs) — Have full prescribing authority in most states and frequently manage respiratory conditions.
Geriatricians — May manage older patients already stabilized on long-term theophylline therapy.
Telehealth providers can also prescribe Theo-24 XR since it is not a controlled substance. However, because theophylline requires periodic serum blood level monitoring (blood draws), patients will still need to visit a local lab for monitoring even if their prescription is managed via telehealth. Platforms like Teladoc, MDLive, and Amazon Clinic are appropriate for established theophylline patients needing refills.
No. Theo-24 XR (theophylline) is not a controlled substance and has no DEA schedule. It can be prescribed by any licensed prescriber — including primary care physicians, nurse practitioners, physician assistants, and telehealth providers — without special DEA registration or restrictions.
Refills are straightforward — theophylline prescriptions can be written with multiple refills and can be transferred between pharmacies easily. There are no federal fill frequency restrictions or quantity limits imposed by controlled substance rules. That said, prescriptions for theophylline should include specific instructions about dose and serum monitoring requirements, as the drug requires careful therapeutic management despite its non-scheduled status.
At therapeutic serum levels (5–15 mcg/mL), most patients tolerate theophylline reasonably well. Common side effects include:
Nausea and vomiting
Headache
Insomnia and trouble sleeping
Irritability and anxiety/nervousness
Fine hand tremors
Increased stomach acid / heartburn (GERD)
Dizziness and lightheadedness
Serious side effects (call your doctor or 911 immediately):
Seizures (life-threatening at toxic levels above 30 mcg/mL)
Rapid or irregular heartbeat (cardiac arrhythmias)
Severe persistent vomiting (sign of toxicity)
Confusion or altered mental status
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Tiotropium (Spiriva)
Long-acting anticholinergic (LAMA) inhaler; preferred for COPD maintenance. Once daily, no serum monitoring required. More expensive than generic theophylline.
Montelukast (Singulair)
Oral leukotriene receptor antagonist; most effective for allergic asthma. Once daily, affordable as generic (~$10–$20/month), no monitoring required.
Fluticasone/Salmeterol (Advair)
ICS/LABA combination inhaler for moderate-to-severe asthma and COPD. Requires inhaler technique; generic available.
Dyphylline
Same methylxanthine class as theophylline; wider safety margin, no therapeutic drug monitoring required. Less potent than theophylline.
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Ciprofloxacin (Cipro)
majorCYP1A2 inhibitor — can double or triple theophylline blood levels, significantly increasing toxicity risk. Avoid if possible; if unavoidable, reduce theophylline dose and monitor serum levels closely.
Erythromycin / Clarithromycin
majorMacrolide antibiotics that inhibit CYP3A4, raising theophylline levels. Use azithromycin as an alternative when possible.
Fluvoxamine (Luvox)
majorPotent CYP1A2 inhibitor used for OCD/depression. Can raise theophylline levels 3-fold or more. Avoid concurrent use.
Riociguat (Adempas)
majorContraindicated — additive vasodilation and dangerous hypotension when combined with theophylline.
Rifampin
majorPowerful CYP inducer used for tuberculosis. Can reduce theophylline levels by 50% or more, potentially making it ineffective.
Phenytoin (Dilantin)
moderateInduces CYP metabolism, lowering theophylline levels. Mutual interaction — theophylline may also affect phenytoin levels.
Cimetidine (Tagamet)
moderateOTC heartburn medication that inhibits theophylline metabolism. Switch to famotidine (Pepcid) or omeprazole (Prilosec) to avoid this interaction.
St. John's Wort
moderateHerbal supplement that induces CYP enzymes, lowering theophylline levels and potentially reducing effectiveness. Avoid while on theophylline.
Theo-24 XR (theophylline extended release) occupies a unique niche in respiratory medicine. It is affordable ($4–$40/month), oral, and has multiple mechanisms of action — bronchodilation, anti-inflammatory effects, and diaphragm strengthening — that benefit certain patients with asthma and COPD who cannot or prefer not to use inhaled therapies.
The ongoing supply shortage — with the 400 mg strength most significantly affected — requires patients and providers to be proactive. Start refills early, explore independent pharmacies and mail-order options, and discuss contingency plans with your prescriber before running out.
If you're having trouble finding Theo-24 XR at your pharmacy, medfinder can help. Enter your medication, dose, and location — medfinder calls pharmacies near you and sends you a list of which ones can fill your prescription, saving you hours of searching.
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