Drug H is most like
The effects of Drug H are changed by treatment with either an alpha or beta blocker, so Drug H must have activity at both receptors (choices B, D, and E are ruled out). "Reversal" of a pressor effect can only occur if the drug has beta2 activity (choice C is ruled out). Drug H is epinephrine.
Epinephrine
Isoproterenol
Norepinephrine
Phenylephrine
A.N.S.