Final answer:
Dopamine exhibits a Dopamine/beta/alpha agonist effect at an infusion rate of 10-20 mcg/kg/min. At this rate, it acts on both beta-1 adrenergic and alpha adrenergic receptors, affecting cardiac output and systemic vascular resistance.
Step-by-step explanation:
The question pertains to the pharmacological effects of dopamine at different infusion rates. Dopamine acts on various receptors at different dose ranges. At low rates of infusion (less than 5 mcg/kg/min), dopamine primarily exerts its effects on dopaminergic receptors (dopaminergic effects), leading to vasodilation primarily in the renal, mesenteric, coronary, and intracerebral vascular beds. At intermediate rates (5-10 mcg/kg/min), it begins to have additional effects on beta-1 adrenergic receptors (beta-1 agonist effects) in the heart leading to increased cardiac output.
However, it is at the higher infusion range of 10-20 mcg/kg/min that dopamine exhibits both beta-agonist and beginning alpha-agonist effects, causing more significant increases in cardiac output and systemic vascular resistance, respectively. At rates higher than 20 mcg/kg/min, the alpha effects become predominant. Therefore, the answer to the question 'At what rate of infusion does dopamine exhibit a Dopamine/beta/alpha agonist effect?' is option c) 10-20 mcg/kg/min