Drug-Induced Neurologic Conditions

Tammie Lee Demler, BS, PharmD, MBA, BCPP


US Pharmacist. 2014;39(1):47-52. 

In This Article

Abstract and Introduction


Pharmacists are trained to recognize the most common adverse effects of drugs; however, any member of the medical team can easily overlook side effects that appear to be new medical conditions. Drug-induced neurologic conditions may result from single-agent drug regimens, but they are more likely to occur when multiple agents that confer risk are administered concomitantly. Educating patients about these risks and remaining vigilant in clinical investigations of unusual adverse effects are key elements to increasing the safety of drug management.


Along with awareness of the improved health outcomes resulting from drug therapy comes the recognition that drug therapy may also contribute to the emergence of new disorders. Mindful consideration of the possibility of drug-induced neurologic symptoms must be part of any ongoing evaluation of the evolving body of evidence obtained through clinical case reports. The emergence of new neurologic side effects of drugs heightens the challenges prescribers face when considering drug therapy. These side effects can result in potential misdiagnoses, including false psychiatric diagnoses, in the case of some drugs. Unexpected and unpredictable drug interactions can result in a confusing range of symptoms that may be identified as a new medical condition.

The term neurologic side effect is commonly used to describe a new drug-induced neurologic syndrome and/or disorder. Pharmacists may not routinely anticipate or recognize these new conditions caused by common drug agents. Changes in the central nervous system (brain, spinal cord) or peripheral nerves can cause a wide variety of symptoms, including loss of coordination and muscle strength, numbness, loss of consciousness, seizures, and paralysis (Table 1).[1–3] In July 2013, the FDA added a black box warning to the antimalarial drug mefloquine about serious neurologic side effects, including dizziness, loss of balance, and tinnitus.[4]

Often, it is difficult to determine whether a neurologic condition is caused by a drug. A key factor to consider when reviewing clinical case reports and/or reporting through MedWatch is clear and consistent identification of the suspect drug, as well as a detailed report of the proposed drug-induced disorder. One of the more difficult aspects of such an investigation is ensuring the specificity of the event related to the drug by ruling out other potential causes of the disorder. Limits in premarketing data make postmarketing surveillance essential to identifying new neurologic side effects of drugs.