Beta-blocker toxicity: a clinical diagnosis.

An overdose of the beta-blocking agent metoprolol is presented in which the patient remained asymptomatic despite blood levels that were more than 25 times that reported to be the upper limit of therapeutic. This case emphasizes the need to diagnose beta-blocker toxicity on clinical grounds, not on blood levels that correlate poorly with the severity of symptoms. Furthermore, the question is raised as to whether patients are at any subsequent risk for morbidity, if they have not demonstrated signs or symptoms within 4 hours of ingestion.