I don't know how much time you have, but I would recommend the lippincott pharmacology review book and pre-test pharmacology. It will require some time on your part, but I think it helped drastically for Step I as well as for clerkships (I got numerous specific comments from professors complimenting my pharm knowledge). Also, know the adrenergic agonists and antagonists cold. Know which receptors they affect and know them well enough to figure out what would happen to blood pressure if X antagonist were given before Y agonist (i.e., giving phentolamine before epinephrine).