Cromolyn is useful in preventing asthma but has limited effectiveness once acute asthma starts. Cromolyn can help prevent asthma triggered by exercise, cold air, and allergic substances, such as cat dander. Cromolyn may be used in children as well as adults. Methylxanthines are administered orally or intravenously. Before the inhalers became popular, methylxanthines were the mainstay of treatment of asthma.
Theophylline can also act as a mild diuretic, causing an increase in urination.
For asthma that is difficult to control, methylxanthines can still play an important role. Dosage levels of theophyline or aminophylline are closely monitored. Excessive levels can lead to nausea, vomiting, heart rhythm problems, and even seizures. In certain medical conditions, such as heart failure or cirrhosis, dosages of methylxanthines are lowered to avoid excessive blood levels. Corticosteroids are given orally for severe asthma unresponsive to other medications.