http://www.postgradmed.com/issues/2002/03_02/fitch2.htm
Here is an article that shows the alpha/beta table.
It also cites a study that showed better results with Levophed:
"Many patients have persistently low blood pressure when receiving dopamine therapy. Evidence suggests that norepinephrine is superior to dopamine in the treatment of hypotension associated with septic shock. Martin and colleagues (14) studied 32 patients with septic shock unresponsive to fluids. They randomly assigned patients to receive a 6-hour infusion of either dopamine or norepinephrine. Fifteen of 16 patients in the norepinephrine group had improved hemodynamics compared with 5 of 16 in the dopamine group. Patients who received norepinephrine had higher urine output and more improvement in lactic acid levels than patients who received dopamine. Several other studies have shown improved splanchnic tissue perfusion with norepinephrine compared with dopamine."