Theophylline toxicity--a consequence of congestive heart failure.

A case is reported of an elderly patient with congestive heart failure (CHF), who was treated with juvenile oral doses of theophylline (Theo-Dur). The patient experienced toxic symptoms, and plasma concentrations were determined. A value of 60.6 micrograms/ml was reported and the theophylline administration was subsequently discontinued. Plasma concentrations and toxicity of theophylline are unpredictable in patients with CHF because of the great variability in clearance. This case demonstrates the necessity for careful monitoring of theophylline plasma levels in CHF patients.