Beta-blockers are a class of common heart or blood pressure medications used in both people and pets. When given as directed, these drugs are life-saving and do a wonderful job of regulating heart problems. If an accidental overdose occurs, however, the outcome can be fatal. There is a very, very narrow margin of safety with any drugs within this class, so even the slightest additional amount can result in heart failure, a decreased heart rate, low blood pressure, and kidney failure. In accidental ingestion cases, or in cases where an overdose of medication may have been given, immediate treatment is necessary.