pulmonary disorders
Drug Treatment of Asthma
Methylxanthines
Methylxanthines relax bronchial smooth muscle (probably by inhibiting phosphodiesterase) and may improve myocardial and diaphragmatic contractility through unknown mechanisms. Methylxanthines appear to inhibit intracellular release of calcium, decrease microvascular leakage into the airway mucosa, and inhibit the late response to allergens. They decrease the infiltration of eosinophils into bronchial mucosa and of T cells into epithelium. has fallen into disuse because of its many adverse effects and interactions compared with other drugs. Adverse effects include headache, vomiting, cardiac arrhythmias, seizures, and aggravation of Gastroesophageal Reflux Disease (GERD) (by reducing lower esophageal sphincter pressure). Methylxanthines have a narrow therapeutic index; multiple drugs (any metabolized by the cytochrome P-450 pathway, eg, macrolide antibiotics) and conditions (eg, fever, liver disease, heart failure) alter methylxanthine metabolism and elimination. Serumtheophyllinelevels should be monitored periodically and maintained between 5 and 15 mcg/mL (28 and 83 micromole/L). 