Vasopressors are drugs which cause constriction of the veins as a result of the contraction of the walls of the vessels. Vasopression is the opposite of vasodilation.
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Hemodynamic Pharmacology of Intravenous Vasopressors
Pharmacological article displays details about vasopressors, how they cause constriction of the blood vessels, and their use as positive inotropes. - Hemodynamic Pharmacology of Intravenous Vasopressors
http://ccn.aacnjournals.org/cgi/content/full/23/4/79
Delves into various vasopressors, including dobutamine, dopamine, pitressin and dispenses details about dosing, IV bolus therapy, and predominant effects. - Vasopressors and Inotropes
http://www.globalrph.com/icu-agents.htm
Offers data regarding vasopressor agents in regards to their treatment of circulatory shock in critically ill patients. - Vasopressors for Shock
http://www.cochrane.org/reviews/en/ab003709.html