How Can You Trust Incomplete Drug Side Effect Information?

Have you ever left the pharmacy with a new prescription and, before taking the first dose, looked it up online to get some idea about side effects? Many people do. They put the name of their medicine into a Google search, add “side effects,” and the lists that appear seem trustworthy. There are neat categories such as “Common Side Effects” and “Less Common,” “Rare,” or “Serious Side Effects.” What few folks realize, though, is that most such searches provide incomplete drug side effect information. The same can be said for TV commercials, though sometimes the list of horrible complications seems awfully long.

We suspect that most people who search for drug side effect information assume that whatever pops up on a Google search is trustworthy. If they dig deeper and see some credible source such as the Mayo Clinic, WebMD, Drugs.com or the Cleveland Clinic, they are even more assured that the side effect information must be credible.

Let me add one more giant caveat. Long lists of side effects are meaningless! Unless you know the likelihood you could experience a given adverse drug reaction you have no way of making sense of a series of side effects. It would be as if a car dealer told you that your brakes could fail, the engine might blow up and sometimes the transmission won’t shift gears properly. In theory, all of those problems could occur…but they are not very likely. Drug side effects, however, are far more common!

Incomplete Drug Side Effect Information Proliferates:

We wonder how many healthcare professionals understand where the information about adverse drug reactions originates. Do they ever question the validity of the data in their computerized databases or the official prescribing information that comes with the FDA’s stamp of approval?

Few individuals realize that drug companies are the primary source for side effect data. Actually, most drug companies now rely heavily on other entities (contract research organizations or CROs) to conduct clinical trials. The primary goal is to prove drug effectiveness and get FDA approval to market a new medicine.

The CROs also collect data on adverse drug reactions. The key to success if you are a pharmaceutical manufacturer, however, is to answer the question: does our drug demonstrate statistical significance compared to placebo? More often than not, the pot of gold at the end of the drug development rainbow (FDA approval) rests more on modest statistical success than clinical benefit. Collection of side effect information often seems like a necessary, but unpleasant, after thought. As you will shortly read, we think that drug companies and CROs have figured out some sophisticated strategies to influence adverse drug reaction data during clinical trials.

One More Ingredient in Incomplete Drug Side Effect Information:

Many clinical trials are surprisingly short-term. Side effects that only show up after many months or years will rarely be detected during initial testing.

A fascinating systematic review and meta-analysis published in The Lancet (November 1, 2025) revealed that most antidepressant drug studies are surprisingly short.

The authors surveyed the medical literature and reported:

“Of 26,252 citations, 151 studies and 17 FDA reports met inclusion criteria. The overall sample included 58,534 participants, comparing 30 antidepressants with placebo. Median treatment duration was 8 weeks.”

Most people take antidepressant drugs for years. The side effects that these researchers uncovered are not typically mentioned:

“The magnitude of some physiological alterations, in particular change in weight, heart rate, and blood pressure is large and clinically relevant.”

Such adverse reactions rarely show up in long lists of common antidepressant side effects. Neither does bone loss or hip fracture. It takes a long time for such an adverse reaction to reveal itself. Bone loss or hip fracture is not the kind of problem a drug company is likely to discover during a short clinical trial designed to obtain FDA approval.

Yet a study from Norway published in the journal Age and Ageing (July, 2013) reported:

“The risk of hip fracture was increased for people exposed to any antidepressant…The risk of hip fracture attributable to exposure to antidepressant drugs was 4.7%.”

A “systematic review and metanalysis” published in Orthopedic Reviews (Oct. 13, 2022) was titled “The Use of Antidepressants is Linked to Bone Loss.”

The authors conclude:

“Our data suggest that SSRIs are associated with a decrease of BMD [bone mineral density]. We aim to raise clinicians’ awareness of the potential association between the use of antidepressants and bone fragility to increase monitoring of bone health.”

How Could Drug Companies Game the Clinical Trial System?

The Food and Drug Administration does not oversee clinical trials. It analyzes the data that is collected. How that data is collected is left up to the drug companies and their “institutional review boards” (IRBs). Do IRB committees pay adequate attention to how a CRO collects side effect information?

My fear is that neither the FDA nor healthcare professionals realize that the pharmaceutical industry has become adept at manipulating the system when it comes to collecting adverse drug reaction data. If the people running a clinical trial ask questions about side effects in certain ways, they may be able to influence the answers that they receive.

The Semaglutide Mystery: Placebo Reactions Reveal a Paradox!

Consider the wildly popular weight-loss drug semaglutide, sold as Wegovy for weight loss and Ozempic for diabetes. Both contain the exact same medication, just marketed differently. According to official prescribing information, diarrhea occurs in 8.8% of patients taking 1 mg of Ozempic. But with the 2.4 mg dose of Wegovy? Suddenly it jumps to 22-30%.

You might think, “Well, that’s a higher dose, so more side effects make sense.” Except here’s where it gets weird.

In clinical trials, researchers always include a “placebo arm”—people who unknowingly inject an inert liquid instead of the real drug. In the Ozempic trials, people getting placebo injections reported diarrhea just 1.9% of the time. But in Wegovy trials? People on placebo reported diarrhea 16-19% of the time.

That’s a 10-fold difference in diarrhea symptoms from an injection containing no active ingredient. The FDA can’t explain this oddity. Neither can we. But I think it reveals something crucial: the way clinical trial managers ask questions and frame symptoms might dramatically influences the answers the researchers get.

Even stranger: Wegovy’s prescribing information warns doctors to monitor patients for depression, suicidal thoughts, and unusual mood changes. The identical drug Ozempic? No such warning. Australia has issued depression warnings for both, but the FDA hasn’t followed suit.

When the FDA Moves at Glacial Speed: The Fluoroquinolone Tragedy

Sometimes the delay between patients reporting problems and the FDA taking action isn’t measured in months or years. It’s measured in decades.

Fluoroquinolone antibiotics (FQs) like Cipro and Levaquin have been on the market for over 30 years. Cipro was approved in 1987; Levaquin followed in 1996. For years, doctors prescribed these drugs for routine sinus infections, bronchitis, and urinary tract infections without a second thought.

But we’ve been hearing from damaged patients since the early 1990s. In 1994, a reader wrote to us about hallucinations after taking Floxin. In 1998, journalist Stephen Fried published Bitter Pills, documenting his wife’s devastating FQ reaction. By 2008, medical journals were identifying psychiatric side effects as a clear “signal” that warranted investigation.

The FDA didn’t require a black box warning about tendon damage until 2008. The warning about potentially permanent nerve damage didn’t come until 2013. And the alert about aortic aneurysms—a potentially fatal complication—wasn’t issued until December 2018.

That’s more than 30 years of prescriptions written while serious, disabling side effects went largely unacknowledged.

The FDA finally stated in 2016 that the serious side effects of fluoroquinolones “generally outweigh the benefits” for routine infections when other options exist. They advised reserving these drugs as last-resort treatments only.

But countless patients learned this too late. People who took “just one or two pills” for a simple UTI or sinus infection developed permanent nerve pain, ruptured tendons, psychiatric breakdowns, and life-threatening vascular damage. One patient group described fluoroquinolone toxicity as:

“an atomic bomb exploding in their bodies, damaging their muscles and scrambling their DNA to the point many are too sick to work, too weak to walk.”

The Singulair Scandal: When Kids Became Suicidal

Montelukast (Singulair) was approved for asthma and allergies in 1998. By 2008, medical journals were publishing evidence of a “possible signal” for psychiatric adverse reactions. Translation: the drug appeared to be causing depression, anxiety, and suicidal thoughts.

How long did it take the FDA to issue its strongest warning—a black box—about these risks? Twelve years. The black box warning finally came in March 2020.

During those 12 years, how many children and adults experienced devastating psychiatric side effects that could have been prevented if they’d been properly warned?

One mother wrote to us:

“My 14-year-old son had been on Singulair for several years when he was diagnosed with depression. The doctor suggested prescribing an antidepressant. When I searched online, I found out that depression is a side effect of Singulair. My son has been off Singulair for about three weeks and is a happy boy again.”

Another parent confirmed this problem:

“My 10-year-old happy child was put on montelukast and became very sad and depressed. As soon as we took him off, his happy disposition returned.”

These weren’t rare reactions to an obscure medication. Singulair was one of the most widely prescribed drugs in America. Millions of prescriptions were written annually. Yet for more than a decade after warning signs appeared in medical literature, the FDA did nothing to require prominent warnings that might have helped families make informed decisions.

Short-Term Steroids and Incomplete Side Effect Information:

Doctors love to reassure patients that short courses of prednisone or methylprednisolone (the Medrol Dosepak) are perfectly safe. “It’s only a week or two,” some say. “The serious side effects only happen with long-term use.”

Except that’s not what the research shows.

A 2017 study in the BMJ analyzed insurance data from more than 1.5 million adults who took steroid pills for less than a month. Even short-term steroid use was associated with serious adverse reactions:

The authors’ concluded:

“Oral corticosteroids are frequently prescribed for short term use in the US for a variety of common conditions and by numerous provider specialties. Over a three year period, approximately one in five American adults in a commercially insured plan used oral corticosteroids for less than 30 days. The short term use of these drugs was associated with increased rates of sepsis [blood infections], venous thromboembolism [blood clots], and fracture; even at relatively low doses.”

The psychiatric side effects can be even more frightening. One reader told us:

“My doctor prescribed Medrol for bronchitis. Within a few minutes of using a steroid inhaler, I started to feel really strange. I wanted to jump out of my own skin! Shortly after I became manic. I don’t remember what followed, but my boyfriend says I flew into a rage, locked myself in my bedroom, and was writing suicide notes with several old bottles of pain meds on the counter. I spent three days in the hospital on suicide watch and don’t even remember doing anything.”

Another young person wasn’t as lucky:

“My 16-year-old family member recently had a psychotic reaction to prednisone prescribed for an asthma attack. He ended up confined to a psychiatric ward for seven days and needed anti-psychotic drugs and psychotherapy for weeks afterward.”

These aren’t long-term steroid users. These are people taking “safe” short courses for common conditions like bronchitis and asthma. But doctors rarely warn patients about psychiatric reactions before writing these prescriptions.

The Side Effects Nobody Mentions: When Medications Change Your Body

Some side effects are so embarrassing or seemingly “minor” that doctors don’t bother mentioning them. But for patients, they can be devastating.

The Beta Blocker Hair Loss Nobody Talks About

Beta blockers like metoprolol, atenolol, and carvedilol are prescribed to tens of millions of Americans for high blood pressure and heart conditions. The prescribing information mentions “alopecia” as a possible side effect, but I suspect that few doctors warn patients about it. A cardiologist may perceive hair loss as a “minor” or “rare” side effect.

One distressed reader wrote:

“I am very upset about this side effect. These drugs are widely prescribed and a huge number of people are taking them. But they make our hair fall out! This is devastating for a woman.”

Is hair loss life-threatening? No! But for many people—especially women—it’s emotionally crushing and affects their quality of life profoundly. When doctors dismiss it as “minor,” they’re making a value judgment that may not match their patients’ priorities.

The Prostate Drug Secret: Penis Shrinkage

Finasteride (Proscar, Propecia) and dutasteride (Avodart) are prescribed to millions of men for enlarged prostates and hair loss. The official prescribing information mentions sexual side effects like reduced libido and erectile dysfunction. What it doesn’t clearly state: these drugs may cause penis shrinkage.

We’ve heard from numerous readers:

“After taking dutasteride for four years I have suffered penis shrinkage, erectile dysfunction, and general libido loss. Basically you have to make a choice. One or the other. The doctors don’t own up to that fact but that’s the reality.”

Another man wrote:

“I have been on dutasteride for 6 years. This has resulted in a dramatic shrinking of the penis which is embarrassing and results in no more erections or orgasms. It bothers me mentally and physically.”

Researchers now recognize “Post-Finasteride Syndrome (PFS)“—a constellation of sexual, physical, and neurologic symptoms that can persist even after stopping the drug, including muscle atrophy, cognitive impairment, depression, and suicidal ideation.

But some clinicians chalk such complaints up to the “nocebo” response. Here is how an Italian dermatologist describes it in a letter to the Journal of Cosmetic Dermatology (May 14, 2025):

“The phenomenon of nocebo responses is well‐documented in medical literature, where negative expectations can lead to the onset or worsening of symptoms—even in the absence of a pharmacological cause. This effect may be particularly pronounced in patients undergoing aesthetic or hair loss treatments, who are often hyper‐focused on physical changes and intensely monitor their bodily sensations. In such individuals, a single alarming testimony encountered online can trigger anxiety and lead to the emergence of symptoms like fatigue or decreased libido—driven more by fear than by pharmacologic action.”

The kinds of problems associated with this class of medications remains controversial. Finasteride was approved by the FDA in 1992 for treating benign prostatic hyperplasia (BPH). The brand name was Proscar. In 1997 it got an FDA green light to treat male pattern baldness under the name Propecia.

In my 1994 edition of the Physicians’ Desk Reference (PDR) here is what the official prescribing information states about Proscar:

“In North American and international clinical trials, 543 patients were treated with 5 mg of PROSCAR for 12 months…only 1 of these patients (0.2%) discontinued therapy with PROSCAR because of a sexual adverse reaction.

The following clinical adversed reactions were reported as possibly, probably or definitively drug related in less or equal % of patients treated for 12 months with 5 mg/day of PROSCAR or placebo, respectively: impotence (3.7%, 1.1%), decreased libido (3.3%, 1.6%)…”

It wasn’t until men started reporting persistent sexual and psychiatric side effects in the early 2000s that researchers started paying attention. In 2025, Mayer Brezis, MD, MPH, wrote a scathing article in the Journal of Clinical Psychiatry (Sept. 22, 2025).

In it he notes some thoughts that reinforce my message in this article:

“Clinical trials are designed to determine efficacy and are inadequate to test safety.

“Why the long delay before determining suicidality risks from finasteride? Why were new tools for postmarketing surveillance applied, well over 10 years since initial reports suggested depression from the drug? Because of this delay, in 2019, post-finasteride syndrome was still thought of as a nocebo effect where patients suffer from delusions related to media coverage, even though adverse events reporting is not usually artificially stimulated, suicide has not been reported with the nocebo effect, and in the case of finasteride, increased awareness of a possible effect on mood appears to have uncovered a real problem.

“Clinical Points:

• “Finasteride, a cosmetic drug widely prescribed for hair loss, may cause depression and suicidality, even after the drug is discontinued.
• There has been a two-decade delay in realizing the extent and gravity of these neuropsychiatric reactions; hundreds of thousands may have endured depression, and many may have died by suicide.”

You can read more about incomplete drug side effect information for finasteride at this link. 

Why the System is Broken and Patients Are at Risk Because of Incomplete Drug Side Effect Information:

The problem isn’t that medications are inherently unsafe. Many are life-saving. The problem is that the system for identifying, tracking, and communicating side effects often fails to keep pace with real-world experience. I also find it disheartening that drug companies design the clinical trials, ask the questions, and report the results.

The FDA reviews this company-generated data and usually accepts it at face value, especially when it comes to adverse drug reactions.

What Can Patients Do About Incomplete Drug Side Effect Information?

1. Clinical trials are short-term. Most run for weeks or months, not years. Side effects that only emerge after extended use are rarely detected before FDA approval.
2. The questions matter. How researchers frame questions about side effects profoundly influences the answers they get. The semaglutide diarrhea mystery illustrates this perfectly.
3. “Common” is meaningless. When prescribing information lists “common side effects,” it provides almost no useful information. Does “common” mean 1 in 10 people? 1 in 100? 1 in 2? Patients deserve actual numbers so they can make informed decisions.
4. The FDA moves slowly. Even when medical journals publish warning signals and patients report serious problems, it often takes the FDA years or decades to issue warnings or require label changes.
5. Post-market surveillance is weak. Once a drug is approved, monitoring for new side effects largely depends on voluntary reporting by doctors and patients. Many adverse reactions go unreported.

What Patients Need to Do:

Until we have a better system—and frankly, don’t hold your breath—patients need to become their own advocates:

Pay Attention to Your Body

Any unusual symptoms that start after beginning a new medication should be reported to your doctor immediately. Don’t assume symptoms are unrelated just because your doctor didn’t warn you about them or they do not appear in the official prescribing information.

Do Your Own Research

Look beyond the first AI-generated paragraph in search results. Seek out:

• Patient forums and support groups where people share real experiences
• Medical journal articles (though they may lag behind patient reports). Go to PubMed for new research
• Independent sources like The People’s Pharmacy that collect patient stories

Ask Direct Questions

Before starting any medication, ask your doctor:

• What percentage of patients experience each major side effect?
• Are there any side effects that might emerge after long-term use?
• What symptoms should I watch for that would require immediately stopping the medication?
• Are there any effects on sexual function, mental health, or appearance I should know about?

Report Your Experiences

If you experience side effects, report them to the FDA’s MedWatch program at www.fda.gov/medwatch. Your report could help protect future patients.

Consider Alternatives

For many conditions, there are multiple treatment options. If one medication causes intolerable side effects, ask about alternatives. Don’t suffer in silence because your doctor insists “this is the best drug” for your condition.

Final Words About Incomplete Drug Side Effect Information:

We wish we could tell you that when your doctor prescribes a medication, you’re getting complete, accurate information about potential side effects. We wish we could assure you that the FDA’s rigorous approval process means all risks are identified before drugs reach the market and what the true percentages are.

The reality is more complicated—and more disturbing. The system for identifying, reporting, and warning about drug side effects is fundamentally broken. Drug companies control the data. The FDA moves glacially. And patients are often left to discover serious complications on their own.

The semaglutide placebo mystery, the decades-long fluoroquinolone tragedy, the 12-year Singulair delay, the hidden risks of “safe” short-term steroids, and the side effects too “embarrassing” to mention—all point to the same conclusion: You cannot blindly trust incomplete drug side effect information.

That doesn’t mean medications aren’t valuable or life-saving. Many are. But it does mean you need to be an informed, vigilant participant in your own healthcare. Ask questions. Do research. Pay attention to your body. Report problems. And never let anyone—doctor, pharmacist, or drug company—convince you that your experience isn’t valid just because it’s not listed in the official prescribing information.

Your body knows what it’s experiencing. Trust it.

Have you experienced side effects that weren’t adequately explained before you started a medication? Share your story in the comments below and help other readers make more informed decisions. 

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