Is a manufacturer of a prescription drug liable for failing to warn of a manufacturing defect?

Under Restatement Second of Torts section 402A, comment k, ⁴ the producer of an unavoidably unsafe product is liable only if the manufacturer of the product "failed to warn of a defect of which it either knew or should have known." (Brown v. Superior Court, supra, 44 Cal.3d 1049, 1059, 245 Cal.Rptr. 412, 751 P.2d 470.) The manufacturer of a prescription drug also would remain liable for a manufacturing defect as well as under general principles of negligence. (Id., at p. 1069, fn. 12, 245 Cal.Rptr. 412, 751 P.2d 470.)