Therapeutic and Toxic Theophylline Levels in Asthma Attacks
Aliza Zeidman, Joseph Gardyn, Zinaida Fradin, Gershon Fink, Moshe Mittelman
Dept. of Medicine B, Rabin Medical Center, Golda (Hasharon) Campus and Pulmonary Institute, Rabin Medical Center, Beilinson Campus, Petah Tikva; and Sackler Faculty of Medicine, Tel Aviv University
Although first-line therapy for bronchial asthma has changed over the past decade to anti-inflammatory medication such as inhaled corticosteroids and cromolyn with possible addition of beta-agonists, theophylline is still useful and therefor widely used. However, several studies have raised serious questions regarding its efficacy in acute asthmatic exacerbations. These studies, the narrow therapeutic range of the drug, the frequency of side effects and interactions with common drugs, and individual variation in clearance and metabolism, have prompted its reevaluation in the management of asthma. Therapeutic serum levels of theophylline are between 10 to 20 mcg/ml. Most adults achieve these concentrations with daily slow-release oral theophylline preparations, 200-400 mg (approximately 10 mg/Kg) twice a day. However, when such a patient presents to the emergency room (ER) in an asthmatic attack, immediate intravenous theophylline is often given, regardless of maintenance treatment. Since the rationale for this common therapeutic approach has been challenged, the current study was undertaken. Serum theophylline levels were measured in 23 consecutive asthmatics presenting to the ER in an acute attack. 15 (68%) had therapeutic levels (above 10 mcg/ml) and 2 had toxic levels (above 20 mcg/ml), prior to receiving the standard intravenous theophylline dose given for an attack. These data indicate that most patients with bronchial asthma on oral maintenance theophylline do not require additional intravenous theophylline when in an attack. It probably will not benefit them and may even induce serious theophylline toxicity.