Thylin

Indications

Theophylline is used to prevent and relieve wheezing and breathlessness in asthma and chronic obstructive pulmonary disease (COPD), including chronic bronchitis and emphysema. It is usually added when inhaled medicines alone do not control symptoms. It is not a rescue medicine for a sudden asthma attack.

How It Works

Theophylline belongs to the methylxanthine group. It relaxes the muscles around the airways so they open wider (bronchodilation), has a mild anti-inflammatory effect, and helps the breathing muscles work.

Dosage and Administration

Theophylline has a narrow gap between a helpful dose and a harmful one, so the dose is set by the doctor for each person, often guided by blood level tests.

• Sustained-release or controlled-release tablets, adults: commonly 200 mg every 12 hours at first, then adjusted by the doctor (often to 300 to 400 mg every 12 hours) according to response and blood levels.
• Plain tablets, capsules and syrup, and all doses for children, older people and people with liver or heart disease: as prescribed.

Swallow sustained-release tablets whole; do not crush or chew them. Take doses at the same times each day. Do not switch between brands or types of sustained-release theophylline without your doctor, because they release the medicine differently.

Interactions

Many medicines change theophylline levels:

• Raise levels (risk of toxicity): Ciprofloxacin, Erythromycin, Clarithromycin, Fluvoxamine, Cimetidine, Allopurinol, Fluconazole, Verapamil, Diltiazem, Propranolol and oral contraceptives. Fever and viral infections such as flu can also raise levels.
• Lower levels (less effect): Rifampicin, Carbamazepine, Phenytoin, Phenobarbital, St John wort, and smoking tobacco.
• Beta blockers such as Propranolol can worsen asthma. With Salbutamol and steroids, potassium may fall too low.
• Large amounts of caffeine (tea, coffee, energy drinks) add to side effects.

Contraindications

• Allergy to theophylline, aminophylline or other xanthines
• Acute porphyria

Side Effects

Common: nausea, stomach upset, headache, trouble sleeping, restlessness, a fast heartbeat, shaking and passing more urine.

Get urgent medical help for persistent vomiting, a very fast, pounding or irregular heartbeat, fits, confusion or severe agitation (these often mean the blood level is too high), or for breathing that gets worse despite treatment.

Pregnancy and Lactation

Use in pregnancy only if the doctor decides it is needed; the dose and blood levels may need closer monitoring. Theophylline passes into breast milk and may make the baby irritable; ask your doctor before breastfeeding, and take the dose just after a feed if advised.

Precautions and Warnings

• Tell your doctor if you have heart disease or an irregular heartbeat, high blood pressure, an overactive thyroid, epilepsy, a stomach ulcer, liver disease, or a fever.
• Tell your doctor if you start or stop smoking; stopping smoking can make levels rise sharply.
• Older people need extra care and often a lower dose.
• Keep your reliever inhaler for sudden attacks.
• Blood tests may be needed to check the level.

Overdose

Overdose is dangerous and can cause severe vomiting, a fast or irregular heartbeat, low potassium, fits and collapse. With sustained-release tablets, symptoms may be delayed for many hours. Go to hospital immediately, even if you feel well.

Therapeutic Class

Methylxanthine bronchodilator.

Storage

Store below 30°C in a dry place, away from light and out of the reach of children.