Chronic Obstructive Pulmonary Disease (COPD) (cont.)

Acetylcholine is a chemical released by nerves that attaches to receptors on the muscles surrounding the airway causing the muscles to contract and the airways to narrow. Anti-cholinergic drugs such as ipratropium bromide (Atrovent) dilate airways by blocking the receptors for acetylcholine on the muscles of the airways and preventing them from narrowing. Ipratropium bromide (Atrovent) usually is administered via a MDI. In patients with COPD, ipratropium has been shown to alleviate dyspnea, improve exercise tolerance and improve FEV1. Ipratropium has a slower onset of action but longer duration of action than the shorter-acting beta-2 agonists. Ipratropium usually is well tolerated with minimal side effects even when used in higher doses. Tiotropium (Spiriva) is a long-acting and more powerful version of Ipratropium and has been shown to be more effective.

In comparing ipratropium with beta-2 agonists in the treatment of patients with COPD, studies suggest that ipratropium may be more effective in dilating airways and improving symptoms with fewer side effects. Ipratropium is especially suitable for use by elderly patients who may have difficulty with fast heart rate and tremor from the beta-2 agonists. In patients who respond poorly to either beta-2 agonists or ipratropium alone, a combination of the two drugs sometimes results in a better response than to either drug alone without additional side effects.

Theophylline (Theo-Dur, Theolair, Slo-Bid, Uniphyl, Theo-24) and aminophylline are examples of methylxanthines. Methylxanthines are administered orally or intravenously. Long acting theophylline preparations can be given orally once or twice a day. Theophylline, like a beta agonist, relaxes the muscles surrounding the airways but also prevents mast cells around the airways from releasing bronchoconstricting chemicals such as histamine. Theophylline also can act as a mild diuretic and increase urination. Theophylline also may increase the force of contraction of the heart and lower pressure in the pulmonary arteries. Thus, theophylline can help patients with COPD who have heart failure and pulmonary hypertension. Patients who have difficulty using inhaled bronchodilators but no difficulty taking oral medications find theophylline particularly useful.

The disadvantage of methylxanthines is their side effects. Dosage and blood levels of theophylline or aminophylline have to be closely monitored. Excessively high levels in the blood can lead to nausea, vomiting, heart rhythm problems, and even seizures. In patients with heart failure or cirrhosis, dosages of methylxanthines are lowered to avoid high blood levels. Interactions with other medications, such as cimetidine (Tagamet), calcium channel blockers (Procardia), quinolones (for example, ciprofloxacin [Cipro, Cipro XR, Proquin XR), and allopurinol (Zyloprim) also can alter blood levels of methylxanthines.

Source: MedicineNet.com
http://www.medicinenet.com/chronic_obstructive_pulmonary_disease_copd/article.htm