Aminophylline

Aminophylline is a pharmaceutical compound that consists of theophylline bound to ethylenediamine, forming a water-soluble salt used as a bronchodilator. It is administered in pharmaceutical contexts to treat or prevent symptoms of obstructive airway diseases such as asthma and chronic obstructive pulmonary disease (COPD), though its use has declined in favor of inhaled agents.

The drug belongs to the methylxanthine class and exerts its effects primarily by inhibiting phosphodiesterase enzymes, which leads to increased intracellular cyclic adenosine monophosphate (cAMP) and consequent relaxation of airway smooth muscle. It also acts as an antagonist of adenosine receptors, which may contribute to bronchodilation and anti-inflammatory effects. Aminophylline can have mild diuretic and central nervous system stimulant properties.

Pharmacokinetics and dosing: Theophylline is rapidly absorbed after administration, and aminophylline is rapidly hydrolyzed to theophylline in the body. It is metabolized in the liver, mainly by cytochrome P450 enzymes (notably CYP1A2), and has a narrow therapeutic index. Therapeutic plasma concentrations are commonly cited as approximately 10–20 mg/L, with toxicity suspected above about 20 mg/L. Dosing is adjusted for age, weight, and comorbidities, and long-term therapy requires monitoring of drug levels.

Adverse effects and interactions: Common adverse effects include nausea, vomiting, insomnia, tachycardia, tremor, and headaches. At higher levels, arrhythmias and seizures may occur. Drug interactions are frequent, as many antibiotics (e.g., ciprofloxacin, erythromycin) and other agents inhibit or induce theophylline metabolism, altering blood levels. Smoking increases clearance, potentially reducing effectiveness.

Current role: Due to the availability of safer and more effective therapies, aminophylline is used infrequently and mainly in resource-limited settings or for selected refractory cases. Contraindications include certain cardiac conditions, peptic ulcer disease, and seizure disorders, with careful monitoring required when used.