The active ingredient in Theo-dur is theophylline. It is in the bronchodilator drug class and works by relaxing the smooth muscle in the lungs and the blood vessels surrounding the lungs. When used regularly, it prevents wheezing and shortness of breath.

Follow all directions given to you by your doctor and read all documents provided, including the full Prescribing Information, FDA-Approved Product Labeling, Instructions for Use, and Medication Guide before using Theo-dur. However, the following is a synopsis of the general guidelines for the use of Theo-dur:

• The tablets should be swallowed whole, and not broken, chewed, or crushed.
• You may see tablet shells in your stool, and this is normal.
• You may need to reduce how much caffeine you consume while on this medication, as this can cause additive side effects such as jitteriness or trouble sleeping.
• Do not use this medication for an acute breathing problem, as it will not work fast enough, unlike an inhaler.
• You may require frequent blood tests to measure drug levels and make sure this drug is safe for you.
• If you miss a dose, skip the missed dose and only take the next dose at the regular time. Do not take double or extra doses.

Some mild or common side effects of Theo-dur seen in clinical trials as compared to placebo include:

• Nausea, vomiting, and abdominal pain.
• Headache.

Some individuals may experience serious side effects while using Theo-dur. These side effects may require immediate medical attention. If you experience any of the following, contact your healthcare provider or seek emergency medical help:

• Signs of overdose: severe nausea/ vomiting, lightheadedness, insomnia, restlessness, rapid heart rate, hearing or vision changes.
• Serious life-threatening allergic reactions, which may present as skin rash, hives, swelling of the face, mouth, or tongue, and/ or trouble breathing (anaphylaxis).

These are not all of the possible side effects of theophylline. You should always seek medical advice from your healthcare provider for any questions or concerns about your medical condition or treatment. Read all patient information, medication guides, or drug information sheets that come with this medication. You can also report adverse effects to the Food and Drug Administration at www.fda.gov/medwatch or 1-800-FDA-1088.

Before starting Theo-dur, it is crucial to discuss any existing health conditions with your healthcare provider. You should be sure that your healthcare provider is aware of all your medical conditions, including:

• Smoking tobacco/ nicotine, or stopping smoking.
• Reduced liver/ kidney function.
• Severe liver disease.
• Heart failure or other heart problems like hypertension.
• A history of or an active peptic ulcer.
• Seizure disorders.
• Thyroid disease.

Hypersensitivity to theophylline or xanthine derivatives.

It should begin working within 8-10 hours after your first dose.

When Theo-dur is taken with other prescription drugs, over-the-counter medications, vitamins, and supplements, it may change how they work or increase the frequency or severity of side effects. Make sure that you tell your healthcare professional about anything that you are taking to avoid any negative drug interactions, including:

• Strong inhibitors of liver enzymes, including propranolol, erythromycin, cimetidine, disulfiram, ciprofloxacin, mexiletine, allopurinol, and oral contraceptives, may increase theophylline levels. You may experience more side effects and be at a higher risk of toxic levels when taking any of these medications with theophylline.
• Strong inducers of liver enzymes, including rifampin, carbamazepine, barbiturates, isoproterenol, or phenytoin, may increase the clearance of theophylline. You may experience lower levels of theophylline when it is used with any of these drugs, meaning it may not be as effective. Smoking while taking theophylline has a similar effect.
• Esketamine may increase the toxic effects of theophylline when used together.

Theo-dur is available in doses of 100, 200, or 300mg extended-release tablets.

It should be stored at room temperature, out of reach of children or pets.

It is manufactured by AstraZeneca.

Yes, and it is also available under the brand names Quibron, Elixophyllin, Uniphyl, Slo-bid, and Theochron.

Barring any serious side effects as listed above, or under the direction of a physician, you should not discontinue this medication abruptly. This could lead to an acute breathing attack.

While it is considered compatible for use during pregnancy, it can interfere with contractions during labour.

Talk to your doctor if you are already pregnant or if you have any plans to become pregnant. They will know or recommend what is best for you.

Theophylline is considered compatible with breastfeeding, though there is a risk of irritability, high heart rate, or vomiting in the infant, which should be monitored.

Talk to your doctor if you are already breastfeeding or if you have any plans to breastfeed. They will know or recommend what is best for you.