Unlike most other manufactured products, prescription drugs and medical devices may cause injury or adverse effects despite the fact that there is no defect in their manufacture. New York law describes these products as being "unavoidable unsafe" because of these potential untoward reactions.

Generally, the manufacturer of an unavoidably unsafe product is liable for the harm its product causes to the ultimate user. However, in the case of pharmaceutical products, the manufacturer discharges its duty so long as the product is accompanied by proper directions for use and adequate warnings as to their potential side effects.

Except where Food and Drug Administration regulations otherwise provide, the manufacturer's duty is to warn the doctor, not the patient. Accordingly, the physician acts as an "informed intermediary" between the manufacturer and the patient. The justification for the informed intermediary doctrine stems from the fact that the doctor's role is to evaluate their patients' specific needs, assess the risks and benefits of available drugs or medical devices, and prescribe and supervise their use. Both the legislatures and the courts have concluded that a warning to the medical profession is viewed as the most effective means to reach the patient. The responsibility then falls to the physician to use the drug according to his understanding of its benefits and risks.

Since the manufacturer's responsibility is to warn the doctor, the manufacturer will be directly liable to the patient for a breach of that duty. It is well established that a manufacturer of pharmaceutical products has a duty to warn of all potential dangers of which it knows or should know and must take those steps that are reasonably necessary to bring that knowledge to the attention of the medical profession.

It is misleading, however, to say that the manufacturer has a duty to warn the "medical profession." It is clear in New York that the duty to warn and the adequacy of the warning extends to the particular patient's treating physicians. If the manufacturer adequately and timely warned those physicians upon whom the patient relied, then the pharmaceutical products were not defective and the manufacturer may not be liable.

The substance of the warning and the effectiveness of the means by which it is communicated depends upon the physician involved. Although the law states that a warning by the manufacturer need be given, this may not always be required. For example, the existing knowledge of the relevant hazard by the treating physician may be so apparent that the lack of an adequate warning would not be considered the cause of the patient's injuries. If the physician prescribed the drug with knowledge of the risk, then the physician may be held liable. Similarly, even if warned, the physician may deliberately disregard the manufacturer's warning in favor of his own knowledge of the drug. On the other hand, the greater the potential unknown danger of the product, the more extensive must be the manufacturer's efforts to make that hazard known to the medical profession.

The important question that arises for physicians is under what types of circumstances will the manufacturer be responsible for the patient's injuries and the doctor free from fault.

First, the duty of the manufacturer to warn the adverse effects is a continuing one, and as such, it requires the manufacturers to keep abreast of the knowledge of its products as gained through research, adverse reaction reports, scientific literature and other available methods. Once the manufacturer avails itself of this knowledge, it must take such steps as are reasonably necessary to bring that knowledge to the attention of the medical profession. The adequacy of a manufacturer's warnings must be judged in light of what it knew at the time the patient was using the product.

Second, the manufacturer must report adverse effects found during premarketing studies. As such, the manufacturer is under a duty to disclose all the information it possesses from the testing required for Food and Drug Administration approval. For example, during the premarketing studies of Talwin it was discovered that a tremendous number of people developed a Talwin addiction. Despite their knowledge of Talwin's addictiveness, the manufacturer did not disclose these findings. Hence, the manufacturer and not the doctor was liable for the patient's injuries since the patient would not have received the same number of injections, would not have been issued refillable prescriptions, and would not have been allowed to self administer the drug if the manufacturer timely and adequately disclosed all the relevant information.

Third, adequately detailing the dangers of a drug in package inserts is not necessarily a sufficient warning. No matter how detailed and accurate the package insert may be, an uncommunicated warning is no warning at all. Package inserts are included within the drug package when it is shipped to the pharmacy. The pharmacist, however, often removes and discards the insert in the process of affixing his own label to the container. Therefore, there is no guarantee that the doctor will see the insert. As such, the manufacturer should convey the danger through other well known methods, such as the Physician's Desk Reference and Dear Doctor letters.

Fourth, downplaying adverse effects or over promotion of a product is yet another way in which the doctor can shift the liability to the manufacturer. For example, the literature describing the product or a manufacturer's sales force may water down references to its possible adverse effects. Likewise, manufacturers may make unsubstantiated claims as to the value of their product, despite the warning in the package insert. The court, in instances such as these, may find the manufacturer rather than the doctor liable.

Finally, manufacturers who encourage off label usage will be held accountable for their actions. If a manufacturer encourages the use of an approved drug for treatment of a condition other than a condition that it was approved to treat, then this renders the drug a "new drug" and FDA approval would be necessary. Accordingly, if the manufacturer encourages a use for which its product is not approved then the manufacturer rather than the physician will be found liable.

The "informed intermediary" doctrine is not an automatic defense for a pharmaceutical manufacturer. Physicians, although they must heed the warnings of a product's potential hazards, are not assumed to know a products' latent dangers unless they are specifically and adequately informed. Physicians rely on the manufacturer's sales representatives to be informed. It is the manufacturer's duty through its literature and sale's representatives, to present a fair and accurate view of their product to the physicians.