These drugs are used in the failing heart to maximise the contractile reserves that exist. They are therefore used in severe heart failure (when intensive monitoring is available). However, they increase the work load and oxygen consumption of the heart. These drugs fall into two broad categories: sympathomimetic drugs and phosphodiesterase inhibitors, but the latter are not readily available and have not been adequately evaluated in animals. The value of methylxanthine agents (see Chapter 22) as positive inotropes is questionable.
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