Beta-blockers are well absorbed and toxic effects usually begin within 30 min of ingestion, peaking within 1 to 2 h. With the exception of sotalol, toxicity is almost always apparent within 6 h (Love 1994b). Toxic effects are listed in Table 1. Patients can deteriorate very rapidly and should be carefully monitored. The most consistent findings are bradycardia and hypotension. The degree of hypotension reflects the severity of toxicity; bradycardia is not useful in assessing toxicity as it occurs at therapeutic levels. Tachycardia has been reported with partial agonists such as pindolol. Progressive pulmonary edema and bronchospasm are uncommon unless there is pre-existing cardiac or respiratory disease. Effects on the central nervous system are unusual with hydrophilic agents such as atenolol. When present, coma and respiratory depression are poor prognostic features and are always accompanied by severe cardiovascular depression. Coma without cardiovascular depression suggests that other substances have been ingested. Although convulsions are seen as part of the central effect, they may also be caused by hypoglycemia.
Table 1 Clinical effects of b-blocker poisoning
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