Well, not literally, of course. While pharmacists have always been doctors' last line of defense against medication errors, a new breed of "specialist pharmacists" may reduce what the Institute of Medicine estimates are at least 1.5 million preventable adverse drug events that occur each year. The specialist pharmacists employed by Medco Health Solutions, whose prescription drug benefit programs cover 60 million people, will review scripts for major chronic conditions including heart disease, high blood pressure, high cholesterol, diabetes, cancer, and asthma. The company says its specialists may consult with doctors from time to time to make sure its members receive the safest and most affordable medications. But whether this proves a help or a hindrance to physicians remains to be seen.