This is the third of a six-part series on liability defenses that every inside counsel should know (Part 1 and Part 2). Based on more than 30 years of litigation practice, this series discusses the liability defenses I have found to most often result in successful summary judgments or dismissals, providing the best potential to end expensive and time-consuming litigation. This installment focuses on the learned intermediary rule.

In general, manufacturers have a duty to warn end users about the known hazards associated with use of their products. The learned intermediary rule provides an exception to this general duty. Under the learned intermediary rule, a product manufacturer's duty to warn about a known hazard runs to an intermediary instead of to the end user of the product. The rule usually applies in circumstances where the intermediary is in the best position to provide warnings to the product's end users, or when there is a significant burden to the product manufacturer to provide a direct warning. The intermediary rule can be used by a product manufacturer to obtain summary judgment or dismissal of a failure to warn lawsuit filed by the end user of a product if appropriate warnings were provided to an intermediary, such as the employer of the end user, or if it can be shown that the intermediary knew the product's hazards.

The learned intermediary rule is most commonly applied in the context of sales of pharmaceutical products. In such cases, the physician serves as a learned intermediary between the pharmaceutical manufacturer and the patient-end user. The pharmaceutical manufacturer fulfills its duty to warn end users of the known risks of its products by providing adequate warnings to the physician intermediaries who prescribe the drug. Once adequate warnings are provided to the learned intermediary-physician, the manufacturer has no further duty to provide warnings directly to end users. The highest courts in more than 35 states and scores of intermediate state and federal courts applying state law have adopted some form of the learned intermediary rule within the prescription drug context or cited favorably to its application.

While the learned intermediary rule is an important defense for manufacturers of pharmaceutical products, it is also significant for manufacturers of other products that are sold and used in industrial or commercial situations. This rule has been applied by courts in many states to provide an exception to the duty to warn end users when products are sold in industrial or commercial settings through sophisticated employers of the products' end users. These court decisions have given rise to two defenses that provide an exception to the duty to provide warnings to end users in industrial or commercial settings: the sophisticated user doctrine and the bulk supplier doctrine.

The sophisticated user doctrine allows a product manufacturer to discharge its duty to warn based on the knowledge or skill of the commercial purchaser of its product, which is often the employer of the end user. This doctrine is asserted in two types of situations:

1. When the product manufacturer provides warning information to the employer with the expectation that it will be transmitted by the employer to the end user employee; and
2. When a manufacturer does not provide a warning to a knowledgeable employer because the employer already knows the hazards of the product.

Under these circumstances, a product manufacturer does not need to provide a warning directly to an end user and instead may rely upon the knowledge of the employer to either pass along the warning from the product manufacturer or provide an appropriate warning based upon the knowledge and sophistication of the employer.

The bulk supplier doctrine is a defense that applies in situations in which industrial chemicals or materials are sold in bulk, often by tanker truck or rail car, and deposited into the employer's storage facilities. In these circumstances, the bulk product is often intermingled with the products of other manufacturers, and it is impossible for the product manufacturer to physically affix a warning to the product. In many jurisdictions, the product manufacturer who sells an industrial product in bulk does not have an obligation to warn the end user of the product, and instead discharges its duty to warn by either providing a warning to the employer or relying upon the employer to provide an appropriate warning to the employee end user.

While the learned intermediary doctrine in the context of pharmaceuticals has received wide support in virtually every jurisdiction in the United States, its acceptance in other commercial situations varies from state to state. However, there is a developing acceptance of the learned intermediary defense in industrial and commercial situations where the end user is employed by a sophisticated employer who either received an appropriate warning or knew the hazards of the product provided to the end user in its workplace. Often in industrial and commercial circumstances, an adequate warning has been provided to the employer of the end user, or the employer was knowledgeable about the hazards of the product. Under these circumstances, a manufacturer should seek summary judgment or dismissal of a failure to warn lawsuit by an end user based upon the warnings provided to the plaintiff's employer or based upon the employer's knowledge and sophistication.