If a doctor fails to warn a patient about a medication risk, the patient may have a claim against the doctor and not the drug manufacturer. This is called the Learned-Intermediary doctrine, which also applies to medical devices. 

The manufacturer can rely on the treating doctor to warn a patient of adverse effects, which are disclosed to the professional through sales representatives, package inserts, and the Physicians’ Desk Reference. 

The treating doctor is expected to use his professional judgment to warn the patient. It is not feasible for the manufacturer to directly warn every patient. (Cardiovasc Ther. 2012 Jun;30(3):e140-5.)