Adrenergic vasoactive agents exert their actions by activation of a-adrenergic, b-adrenergic, and dopamine receptors ( Rudisefa/ 1996). They all have a half-life of 2
to 3 min, enabling a steady state to be reached within 10 to 15 min, and are rapidly metabolized to inactive metabolites. The benefits and side-effects of any particular drug will depend on which receptors they act on (T§ble..„2.). The degree of response to adrenergic agents varies widely as it depends on many factors, and so the patient's response should be carefully monitored. Chronic sympathetic stimulation can lead to a decrease in the number and function of adrenergic receptors, which may limit a patient's response to catecholamines. Inflammatory mediators can also result in a decreased response of adrenergic receptors to stimulation. The dose ranges of some vasoconstrictor agents are given in Table.3.
Table 2 Effects of stimulation of adrenergic or dopamine receptors on various organ systems
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