Fluoroquinolone‐Associated Dysglycemias: A Tale of Two Toxicities

In this issue of Pharmacotherapy, Dr. Mohr and colleagues 1 and Dr. Graumlich and colleagues 2 evaluate the impact of fluoroquinolones on perturbations in blood glucose concentrations, namely, hypoglycemia and hyperglycemia. In this editorial, I elaborate on the tale of two toxicities, that is, hypoglycemia and hyperglycemia. Charles Dickens, in his famous book with a title similar to this editorial's, opened with the sentence, "It was the best of times, it was the worst of times." Similar to Dickens' book, which was set in 1775, it is the best of times-the stringency with which drugs are scrutinized from a toxicologic perspective has significantly increased-and it is the worst of times-10.2% of drugs approved by the United States Food and Drug Administration (FDA) during the past 20 years have received one or more black-box warnings after approval. he literature has offered a steady diet of postmarketing safety and toxicity studies over the last several years for clinicians to digest. After FDA approval of a drug for general use, unusual and serious events-such as hepatic toxicity, seizures, toxic epidermal necrolysis, cardiac toxicity (including torsade de pointes), to name a few-may be identified from these studies and from voluntary, spontaneous reports of adverse drug reactions (ADRs) to the FDA. Although identification of signals related to these ADRs may occur after approval, difficulties arise when attempts are made to compare incidence rates or determine causality. Because studies cite incidence rates, it can become confusing when two or more studies yield apparently dissimilar rates of occurrence for the same ADR.