Not quite. Vasoconstriction is the body constricting the flow of blood by narrowing the blood vessels.
http://en.wikipedia.org/wiki/Vasoconstriction
...and as regards keeping warm, I only say this because I know that it works for me. I am not saying wrap yourself up in 20 layers of clothing, just keep yourself at a nice temperature. As I said, in my experience keeping warm and hydrated minimises vasoconstriction. There may be some physiological reason for this, but I'm not sure what it is...
Vasoconstriction can be a physiological response to cold - to preserve core body temperature your body diverts blood away from the extremities and the skin, where a lot of heat is lost. So if you have drug induced vasoconstriction and you are also cold I imagine it would make the problem worse.. then again I can see that it would not be good to be too hot either, in case you become hyperthermic. Comfortable temperature sounds about right!