Dear Dr. Prescott,
I worry about taking new medications for fear of unknown side effects. I see that we’re starting to use older drugs in new ways more often these days. What are the advantages to this trend?
Larry Hawkins, Oklahoma City
Existing drugs are typically less expensive than medications that have recently arrived in pharmacies and clinics. This is because the modern research, development and testing process is considerably more complicated, time-consuming and, as a result, pricey.
Newer drugs don’t yet have an extensive track record developed by use in clinical practice. But the Food and Drug Administration’s approval process requires at least three (and, increasingly, four) phases of testing in which scientists monitor experimental medications for potential side effects. So, even if they have only recently become available to most patients, these drugs have undergone a years-long surveillance process.
That process, though, has involved a limited number of patients. So, when larger numbers of people receive the drug, new issues might emerge. And when scientists have more extensive pools of patient data to analyze, they might also find a pattern in adverse events previously thought unrelated to the drug.
However, I don’t want you to think new drugs are dangerous. To the contrary, the medications we develop today are based on scientific understanding that was unthinkable even a decade ago. These therapies are not “blunt instruments” that physicians once used. Instead of hitting a swath of biological targets, their aim is laser-focused. As a result, this limits collateral damage.
While older drugs have been in use longer, the testing processes they underwent were much less probing. Indeed, the oldest drugs—those that came on the market before 1938—never received FDA approval. They were simply “grandfathered” in based on prior availability.
While we think of these drugs as safe, they often don’t have the same rigorous testing history as newer entrants to the medical marketplace. As a result, when we repurpose (or, technically, reposition) them for use in new conditions, we can see unexpected or amplified side effects.
A case in point is the drug hydroxychloroquine. Doctors used it for more than a half-century as a treatment for malaria and, more recently, for autoimmune diseases like lupus and rheumatoid arthritis. But after physicians began prescribing it much more frequently as a potential treatment for Covid-19, the drug was tied to increased numbers of a potentially fatal heart arrhythmia. While hydroxychloroquine was considered generally safe in most patients, doctors now fear its potential to cause abnormal heart rhythms—a known risk—could prove especially dangerous for severely ill Covid-19 patients, who may have organ damage from the virus.
Legally, doctors can prescribe existing medications for “off-label” use as they see fit. Still, clinical trials represent the most effective way to test whether an existing medication might safely treat additional illnesses. As a patient, before I use any medication old or new, I feel best knowing it’s undergone that process for the specific condition I’m suffering from.
