If you go skydiving, you know there is a chance, however remote, that your parachute will not open. This is an extreme example of assuming the risk, a legal principle that is a viable defense in many products liability cases.
Most medical patients will want to know what is in a pill before they take it, or what a surgery will entail before they agree to go under the knife. It is natural to want to be informed about a medical procedure before submitting to it, because of the fear of the unknown.
Manufacturers and sellers of defective products may be liable for any injuries caused by that defect, but only when the injured people used the product in a foreseeable way. In fact, saying the plaintiff misused the product is a viable defense to many products liability lawsuits in Ohio.