Side effects of medications are common and often quite bothersome.
Serious side effects, such as severe or even life-threatening allergic reactions, require immediate treatment and discontinuation of the medication. Milder symptoms may be tolerable compared to the benefit of the medication. And sometimes they go away on their own as the body gets used to the medication.
But there is another type of side effect that you hear about much less: the positive ones. Although they are rare, you should keep them in mind when you start taking a new medication.
Aren't all side effects bad?
The term side effect is usually thought of as something bad. And that’s usually true. But that leaves out the “good” side effects. There is relatively little publication about them, so it’s not clear how common they are. But four notable examples are:
Minoxidil (Rogaine, Gainextra, other brands). This drug was developed in the 1970s for high blood pressure and also increased hair growth in study participants. What was initially considered an annoying side effect eventually became its main use: local forms of this drug are often used to treat hair loss.
Diphenhydramine (Benadryl or generic). This common allergy remedy has drowsiness as a side effect. For adults with allergy problems and sleep disorders, the sedative effect may be helpful. Regular, long-term use of diphenhydramine is not recommended, as it may increase the risk of dementia.
Sildenafil (Viagra or generic). Originally developed as a treatment for high blood pressure and angina, it didn’t take long for male users to realize that the drug could induce erections within 30 to 60 minutes. Sildenafil’s makers realized that this could be an extremely useful side effect under the right circumstances, and in 1998 it was approved as a treatment for erectile dysfunction.
Semaglutide (Ozempic, Wegovy, Rybelsus). This drug was developed to treat diabetes, but early users noticed a decreased appetite and significant weight loss. Several formulations of these related drugs are now approved for diabetes and/or weight loss.
In the best study I’ve read on the subject, researchers found more than 450 reports of incidental positive effects of various drugs since 1991. And that may be an underestimate, because the reporting forms didn’t specifically ask about or flag this type of side effect, the study authors said.
Bright spots: Drug repurposing and repackaging
While the discovery of helpful drugs can happen unexpectedly, drug developers are increasingly taking a more targeted approach: They use side effect profiles to look for new uses.
For example:
A drug reported to cause less sweating as a side effect may be effective against hyperhidrosis, a condition characterized by excessive sweating.
Drugs reported to cause low blood pressure as a side effect could be effective treatments for high blood pressure (hypertension).
New treatments for breast cancer may include older drugs that have a similar side effect profile to known cancer drugs.
The availability of large side effect registries has made this method of identifying drugs for repurposing a more realistic option. So even negative side effects can have positive sides.
Bad side effects and the nocebo effect
While side effects can be positive, most are not. Drug side effects are a common reason people don’t take prescribed medications regularly. And drug side effects lead to up to 8% of hospital admissions, according to one analysis.
To make matters worse, in some cases, expecting side effects seems to make them more likely to occur. The so-called nocebo effect increases the likelihood of experiencing a negative side effect and appears to be at least partly due to expectations. Compare this to the placebo effect, where a sugar pill or other inactive treatment can result in a benefit.
Conclusion
Many people avoid taking medications because they fear potential side effects. That’s understandable. But not taking a medication can mean missing out on its benefits. And expecting side effects can increase the likelihood that you’ll get them.
While it’s important to be aware of the most common side effects of the medications you’re taking, it’s also important not to overestimate the likelihood of getting them. And remember: There’s always a chance you’ll get a side effect you actually welcome.