c. Bronchodilator Agents (Xanthine derivatives). The methylxanthines
(theophylline and derivatives) directly relax the smooth muscle of the bronchi and
pulmonary blood vessels. They may also reduce the fatigability and thereby improve
contractility in patients with chronic obstructive airway disease. Xanthine derivatives are
often used in the treatment of apnea and bradycardia of prematurity in infants.
(1) Aminophylline. Aminophylline is a xanthine derivative containing ~80%
theophylline. It is prescribed as a bronchodilator to treat asthma. It will also relieve
bronchospasms associated with emphysema and bronchitis. Aminophylline may be
administered orally or rectally to prevent severe attacks of bronchial asthma but is
generally administered intravenously (I.V.) to relieve acute bronchospasms or status
asthmaticus resistant to adrenergic drugs.
(2) Theophylline (Theolair, Slo-Phyllin, Theodur). Theophylline is often
prescribed as the xanthine of choice for oral administration (tablets, capsules, elixir,
syrup, or solution). One must take care when dispensing theophylline products. Each
different brand varies in the actual amount of theophylline contained in the product and
in the duration of action. Theophylline is a drug with a very narrow therapeutic index
(the treatment dose is very close to the toxic dose). For this reason, patients should
have their theophylline blood levels monitored on a routine basis.
d. Miscellaneous Respiratory Agents.
(1) Cromolyn (Intal). Cromolyn is a unique product that works by inhibiting
the release of histamine and other spasm-causing compounds from mast cells located
in the lungs and prevents bronchoconstriction. It is used mainly for the treatment or
prevention of mild bronchospasms associated with asthma. It is available as an
inhalation aerosol and nebulization solution.
(2) Leukotriene modifiers. The production of leukotrienes (immunologic
proteins) and the binding of leukotriene receptors appears to be responsible for airway
edema, smooth muscle constriction and altered inflammatory processes contributing to
the signs and symptoms of asthma. For this reason, several new agents have been
(a) Zafirlukast (Accolate), montelukast (Singulair). Both of these
agents are leukotriene receptor antagonists which cause inhibition of
bronchoconstriction. Zafirlukast is available as a tablet prescribed twice daily.
Montelukast is prescribed as a once daily tablet.
(b) Ziluton (Zyflo), Ziluton works a little differently in that it inhibits the
formation of leukotrienes to prevent bronchoconstriction. Ziluton is administered four