What Is the Mechanism of Action of Aminophylline?

Aminophylline is a bronchodilator used in the treatment of asthma, chronic bronchitis and emphysema. Aminophylline relaxes smooth muscle (bronchodilation) and controls the body's response to airway stimulation, such as allergens.

Related Compounds

Aminophylline is classified as a xanthine derivative and is structurally related to caffeine and theobromine.

Formulation

Aminophylline is a 2:1 combination of theophylline and ethylenediamine. The ethylenediamine is inactive, but increases the solubility of theophylline in water. Aminophylline is less potent and shorter-acting than theophylline.

Mechanism of Action

Aminophylline inhibits phosphodiesterase (PDE), which increases intracellular cyclic adenine monophosphate (cAMP). This leads to a release of epinephrine from the adrenal medulla cells. Aminophylline also blocks adenosine receptors that mediate the constriction of airways. These actions cause bronchodilation, diuresis and stimulation of the central nervous and cardiac systems, and also increase gastric acid secretion.

Pharmacokinetics

Food slows the absorption of aminophylline. Aminophylline crosses the placenta and enters breast milk; it is classified as Pregnancy Category C (benefits may outweigh risks). Aminophylline is metabolized by the liver and excreted from the body by the urine.

Uses

Aminophylline is used to treat reversible airway obstruction and bronchospasm. It can also be used to treat apnea and bradycardia in neonates.

References

• DiPiro JP, Talbert RL, Yee GC, Matzke GR, Wells BG, Posey LM, eds. Pharmacotherapy: A pathophysiologic approach. 5th ed. New York, New York: McGraw-Hill; 2002.
• Lacy CF, Armstrong LL, Goldman MP, Lance LL. Drug information handbook. 11th ed. Hudson, OH: Lexi-Comp; 2003.

Resources

• Aminophylline information from the NIH
• Aminophylline nformation from the University of Maryland Medical Center