I'm trying to figure out a typical range of physiological concentrations for pharmaceutical drugs. I'm looking through papers that report candidate drugs administered to cell cultures; these papers report LD50 concentrations anywhere from 1 to 100 μM. I don't have any pharmacology experience so I don't know how these numbers compare to commercially available drugs (I realize that different drugs have different toxicities but there must be some ballpark figure). I calculated one such figure by using this clinical study for Herceptin, which reported a serum concentration of 123 μg/mL at a dosage of 2 mg/kg, which I converted to ~0.8 μM (MW 145531.5 g/mol). This seems to be in accord with the dosage recommendation. Is the ~1 μM figure a good concentration to look for in these papers? If no, why not? Thanks for any help.