The pharmacist as expert witness: Not always

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Pharmacists are qualified to serve as expert witnesses in litigation involving pharmacy standards. Increasingly, pharmacists are also being used as expert witnesses in other types of legal cases that do not directly involve pharmacy. Judges will allow such pharmacist expert witness testimony, within limits.

Two cases from March 2013, one from a state appellate court in Maryland and the other from a federal court in Louisiana, help define the circumstances under which a pharmacist may be qualified as an expert witness when the case is not a pharmacy standards case.

The Maryland case

A pharmacist was offered as an expert witness on informed consent in a case brought against the physician of a patient who died as the result of an adverse drug reaction. The patient, who was diagnosed with prostate cancer, had been administered the drug amifostine as a cytoprotective agent to reduce the risk of radiation-induced injury. The patient had a reaction to the drug, resulting in Stevens–Johnson syndrome and death.

At trial, the plaintiffs sought to use the testimony of the pharmacist to show that the physician did not adequately obtain the patient’s informed consent. The trial judge refused to allow the jury to hear this expert testimony, ruling that the pharmacist “did not have the ability to give the full demarcation of what was involved in informed consent” and that his testimony would “confuse and disenchant the jury in their ability to determine what the doctrine of informed consent denoted.”

Without hearing the pharmacist’s testimony, the jury held in favor of the defendant, and the plaintiffs appealed. The appellate court reversed the judgment, ruling that the trial court should have allowed the pharmacist to testify as an expert witness.

The appellate court reviewed previous legal cases related to the admissibility of pharmacist expert testimony. The court agreed with previous cases holding that a pharmacist is “not qualified to testify as to a physician’s negligence.” The court also agreed with cases holding that a “pharmacist is qualified to testify about a drug’s properties, possible side effects, and known material risks, which are factors in informed consent actions.” The court reasoned that the pharmacist offered as an expert “possessed sufficient experience to opine about the material risks of amifostine.” The case was sent back to the trial court.

The Louisiana case

A patient brought a product liability case against the manufacturer of moxifloxacin, alleging that two doses had caused her peripheral neuropathy. The patient relied on the proposed expert witness testimony of a pharmacist, which the defendant challenged as inadmissible.

The court agreed with the defendant, concluding that the pharmacist’s proposed testimony that moxifloxacin can cause peripheral neuropathy was nothing more than a hypothesis. The court noted that the pharmacist “could not point to any epidemiological study that had studied whether Avelox [i.e., moxifloxacin] is associated with peripheral neuropathy.” Regarding the pharmacist’s reliance on reports of peripheral neuropathy associated with other fluoroquinolones, the court noted that the law has “generally rejected the idea that an expert can extrapolate causation to a medication simply due to its being part of a class.”

The court was critical of the pharmacist’s use of the “Naranjo method,” which he used to deduce from adverse event reports that moxifloxacin had “more likely than not” caused the patient’s peripheral neuropathy. The court noted that “the Naranjo algorithm/methodology appears, in actuality, to be a classification system, not a method used to determine actual causal relationships and/or causality assessments.”

The pharmacist was prepared to testify that the defendant should have added a black box warning of peripheral neuropathy to the drug’s labeling, yet when asked whether he knew the FDA standards for the addition of black box warnings, he admitted that he did not.

The court ruled that the pharmacist’s testimony was not based on sufficient evidence, was not the product of a reliable methodology, and should not be allowed at trial.


Pharmacists clearly have expertise in patient education, which is a core pharmacy responsibility. From this practice expertise to expert witness qualification on issues related to informed consent is a logical step. Pharmacists also have knowledge of the general incidence of adverse drug events, although they rarely examine patients to determine whether a specific event was caused by a specific drug. Courts are appropriately reluctant to allow expert testimony by pharmacists on the issue of causation.

Based on: Fusco v Shannon, 2013 Md.App. LEXIS 29 (March 20, 2013), Rhodes v. Bayer Healthcare, 2013 U.S.Dist. LEXIS 44670 (WD La. March 26, 2013).

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