50 Bizarre Side Effects of Common Medicines

Medicine saves lives every day, combating everything from infections to chronic pain. But the little-discussed reality is that adverse drug reactions are the third leading cause of death in the US, claiming over 250,000 lives annually.

Even more insidious, side effects can emerge months or years after starting—or stopping—a medication, long after you've forgotten about it, as seen with delayed tendon damage from antibiotics or bone issues from osteoporosis drugs.

These delayed reactions highlight how drugs can ripple through the body in unexpected ways, affecting organs and systems far beyond their intended target.

From hormonal havoc to bizarre behavioral shifts, here are 50 peculiar side effects that remind us: while medicine helps, it can also unleash chaos we never saw coming.

Read on for details.

1-10: Hormonal and Body Havoc

• Gynecomastia (male children and adults growing breasts) from anti-psychotic drugs: This condition involves the abnormal growth of breast tissue in males, often due to a hormonal imbalance where estrogen levels rise relative to testosterone, leading to swelling and tenderness.

At CBS News and for my TV program “Full Measure,” I covered the story of Risperdal (risperidone) causing this effect in boys as young as age 5 who then required mastectomies. Risperdal is an antipsychotic medication primarily used to treat schizophrenia, bipolar disorder, and irritability in autism. But it’s been widely prescribed “off-label.”

Initially, the drugmaker denied that breast growth was a potential side effect, but after a number of lawsuits, gynecomastia was added to Risperdal’s warning label.

Risperdal can cause this side effect by elevating prolactin levels, a hormone that stimulates breast development. It’s been reported in up to 2.3% of male patients on the drug.

Some male patients also report turning from heterosexual into gay while suffering this side effect on Risperdal.

It’s unknown what harm the drug could do in female patients, for whom the breast growth would be less likely to be flagged as so damaging, but would also be experiencing disruption in the body's delicate endocrine balance.

Other culprits that can cause gynecomastia include spironolactone, a diuretic prescribed for high blood pressure, heart failure, and fluid retention. It blocks androgen receptors and has been linked to gynecomastia in about 10% of users. Anti-androgens like finasteride for prostate issues or hair loss can also trigger it by suppressing testosterone.

• Priapism (painful, prolonged erection) from antidepressant: Priapism is a medical emergency characterized by a persistent, painful erection lasting more than four hours without sexual stimulation, which can lead to permanent tissue damage and erectile dysfunction if not treated promptly.

This side effect is associated with trazodone, an antidepressant commonly used to treat major depressive disorder and insomnia by affecting serotonin levels in the brain.

Reports indicate the painful, prolonged erection occurs due to the drug's alpha-adrenergic blocking properties, which disrupt normal blood flow regulation in the penis, and it's more common in men with underlying conditions like sickle cell anemia.

Immediate medical attention, such as aspiration or surgery, is often required to prevent long-term complications.

• Galactorrhea (unwanted milk production in men and women) and fertility issues from antipsychotics: Galactorrhea refers to the inappropriate leakage of milk from the breasts in men and in women who are not breastfeeding.

This side effect is often accompanied by breast tenderness and irregular periods in women or gynecomastia in men. It's frequently linked to Risperdal and other antipsychotics like haloperidol, which are used for treating psychotic disorders such as schizophrenia by blocking dopamine receptors, thereby increasing prolactin secretion from the pituitary gland.

This hormonal surge can persist even after discontinuing the medicine, affecting fertility and requiring endocrine evaluation.

• Black hairy tongue from antibiotics: This harmless but alarming condition causes the tongue to develop a dark, furry appearance due to overgrown papillae (tiny projections on the tongue) trapping bacteria, food, and dead cells, often leading to bad breath and altered taste.

It's commonly triggered by broad-spectrum antibiotics like penicillin, which are prescribed for bacterial infections such as strep throat or skin infections by killing off harmful bacteria but also disrupting the mouth's natural microbial balance.

Good oral hygiene, like brushing the tongue, usually clears it up within days, but it serves as a reminder of how antibiotics can inadvertently promote overgrowth of non-pathogenic organisms.

• Blue urine or skin from antidepressants: This unusual discoloration can manifest as blue or green-tinted urine, sweat, or even skin, resulting from the drug's metabolites interfering with pigments in bodily fluids, which is typically benign but startling.

Amitriptyline, a tricyclic antidepressant used for depression, chronic pain, and migraines, can cause this due to its chemical structure affecting how the body processes dyes. It's more noticeable in long-term users and usually resolves upon stopping the medication.

• Photosensitivity (extreme sun sensitivity) from antibiotics: Photosensitivity makes the skin highly vulnerable to UV rays, causing exaggerated sunburns, rashes, or blistering even with minimal sun exposure, as the drug acts as a photosensitizer in the skin.

Tetracycline antibiotics, often prescribed for acne, respiratory infections, and Lyme disease, trigger this by forming reactive compounds under sunlight that damage skin cells. Preventive measures like sunscreen and protective clothing are essential, as repeated episodes can lead to premature aging or increased skin cancer risk.

• Weight gain from mood stabilizers: This side effect involves significant, unintended weight increase due to altered metabolism, increased appetite, or fluid retention, which can exacerbate health issues like diabetes or heart disease.

Valproic acid, a mood stabilizer and anticonvulsant used for bipolar disorder, epilepsy, and migraines, causes this by influencing insulin resistance and fat storage pathways.

Patients may gain 10-20 pounds within months, necessitating dietary monitoring and possible medication adjustments.

• Hair loss or color change from chemotherapy: Medications can cause telogen effluvium, where hair follicles enter a resting phase leading to shedding, or alter melanin production resulting in premature graying or color shifts.

Chemotherapy drugs like doxorubicin, administered for various cancers such as breast or lung cancer, damage rapidly dividing hair follicle cells, often causing complete hair loss that's reversible post-treatment. Emotional support is vital, as this visible change can impact self-esteem during an already challenging time.

• Nail detachment from antifungal medicine: Nails may turn yellow, brown, or white, or even separate from the nail bed (onycholysis), due to disrupted keratin production or inflammation.

Fluconazole, an antifungal medication for treating yeast infections, thrush, or systemic fungal issues, interferes with nail matrix function, leading to these changes that typically resolve after discontinuation. It's more common with prolonged use, and patients should avoid trauma to affected nails to prevent secondary infections.

• Excessive sweating from painkillers: Known as hyperhidrosis, this involves profuse, uncontrollable sweating that can soak clothing and cause social embarrassment, stemming from disrupted autonomic nervous system regulation.

Opioids like morphine, used for severe pain management in conditions like cancer or post-surgery recovery, can trigger this by affecting thermoregulatory centers in the brain.

11-20: Sensory Surprises and Losses

• Deafness or hearing loss from Covid vaccine: This can manifest as sudden sensorineural hearing loss (SSNHL), a rapid decline in hearing ability often in one ear, due to potential inflammation or autoimmune responses affecting the inner ear.

The Covid-19 vaccine, originally falsely promoted to prevent infection, illness and transmission, has reports of this side effect, possibly linked to immune activation.

Prompt steroid treatment may restore hearing in some cases, but permanent loss can occur.

• Deafness from MMR vaccine: Similar to SSNHL, this involves damage to the auditory nerve, leading to partial or complete hearing impairment.

The MMR vaccine for measles, mumps, and rubella has been associated with instances of hearing loss, often following the mumps component mimicking the virus's natural effect on the ear.

• Deafness from rabies vaccine: Hearing loss here may stem from an inflammatory response to the vaccine's components, affecting the cochlea or auditory pathways.

The rabies vaccine, crucial for post-exposure prophylaxis against a nearly always fatal viral infection, occasionally reports this adverse event, typically resolving but requiring monitoring.

• Deafness from hepatitis B vaccine: This side effect involves sensorineural hearing loss, possibly from immune-mediated damage.

• Tinnitus (ringing in ears from aspirin): Tinnitus is a persistent perception of noise like ringing or buzzing without an external source, often debilitating and linked to auditory nerve irritation.

High-dose aspirin, used for pain, inflammation, and heart protection, can cause this by affecting cochlear blood flow and neurotransmitter balance. Dose reduction usually alleviates it, but chronic cases may need sound therapy.

• Loss of smell or taste from nasal sprays: Anosmia (loss of smell) and ageusia (loss of taste) can result from direct damage to olfactory or gustatory nerves, impacting quality of life.

Zinc nasal sprays, over-the-counter remedies for colds, have caused permanent loss by toxic effects on sensory cells. The FDA has warned against their use, recommending oral zinc instead.

• Nightmares and night terrors from anti-smoking medicine: These intense, nightmare-like dreams disrupt sleep and can lead to daytime fatigue, arising from altered REM sleep patterns.

Chantix (varenicline), a smoking cessation aid that blocks nicotine receptors, changes brain chemistry, increasing dream vividness in about 13% of users.

• Color blindness or vision changes from Ozempic and Viagra: This includes temporary color distortions like seeing yellow halos, due to retinal toxicity.

Digoxin, a heart medication for atrial fibrillation and heart failure, builds up and affects cone cells in the eye. It’s also widely reported in erectile dysfunction medicines like Viagra and in weightloss and diabetes drugs like Ozempic and Wegovy.

• Retinal detachment from antibiotics and Covid vaccine: Retinal detachment is when the retina pulls away from the eye's supportive tissue, causing vision loss if untreated, linked to weakened connective tissues.

Fluoroquinolone antibiotics like ciprofloxacin, for bacterial infections such as UTIs or pneumonia, degrade collagen, raising this risk alongside tendon issues.

Retinal detachments have also been reported associated with Covid vaccines. Symptoms like floaters warrant immediate eye care.

• Hallucinations from antidepressants and other meds: Visual or auditory hallucinations involve perceiving non-existent stimuli, often from central nervous system disruption.

Antidepressants, anti-seizure medicine, antihistamines, antivirals, and other medicines report side effects that can cause psychiatric symptoms in patients.

21-30: Causing What They ‘Prevent’

• Shingles from chickenpox vaccine: Shingles is a painful rash from reactivation of the varicella-zoster virus, the same as chickenpox, causing nerve pain that can last months.

The varicella vaccine, given to prevent initial chickenpox infection in children, can lead to latent virus reactivation later in life, though some sources debate direct causality and claim it's far less common than from natural infection.

• Worsened depression from antidepressant SSRIs: Paradoxically, these drugs can deepen depressive symptoms, including hopelessness and low energy, due to serotonin fluctuations.

Selective serotonin reuptake inhibitors like Prozac, prescribed for depression, anxiety, and OCD, may cause this "activation syndrome" in the first weeks, affecting up to 10% of patients.

• Suicidal thoughts from antidepressant SSRIs: Increased suicidal ideation, particularly in young adults, stems from heightened agitation before mood stabilization.

Drugs like Paxil carry black-box warnings for this risk in those under 25, used for major depressive disorder and panic attacks.

• Violent thoughts from anxiety meds: Disinhibition can lead to aggressive impulses or irritability, opposite to calming effects.

Benzodiazepines like Xanax, for short-term anxiety or panic, alter GABA receptors, causing this in rare cases, especially with alcohol. Long-term use is discouraged.

• Insomnia from sleep aids: Rebound insomnia worsens wakefulness after discontinuation, due to dependency on the drug's sedative effects. Ambien (zolpidem), for short-term insomnia, disrupts natural sleep cycles, leading to this paradox in chronic users.

• High blood pressure from blood pressure meds: Abrupt withdrawal can cause rebound high blood pressure spikes, exceeding pre-treatment levels. Beta-blockers like atenolol, for hypertension and angina, suppress the sympathetic system, but stopping suddenly unleashes it.

• Allergic reactions from allergy meds: Ironically, antihistamines can trigger hives or swelling in hypersensitive individuals via immune rebound. Diphenhydramine (Benadryl), for allergies and motion sickness, rarely causes this.

• Constipation from laxatives: Overuse leads to bowel dependency and worsened constipation upon stopping, as the gut loses natural motility. Stimulant laxatives like senna, for occasional relief, irritate the intestines, creating a cycle of reliance. Fiber and hydration are better long-term solutions.

• Agitation from sedatives: Instead of calm, some experience hyperactivity or restlessness, particularly in children or elderly. Barbiturates, once used for seizures or anxiety, overstimulate in certain brains, now largely replaced by safer options.

• Worsened pain from painkillers: Opioid-induced hyperalgesia heightens pain sensitivity over time, making discomfort more intense. Oxycodone, for chronic pain, alters pain pathways, necessitating rotation or non-opioid therapies.

31-40: Mental and Behavioral Oddities

• Suicidal ideation from acne meds: Thoughts of self-harm emerge from brain chemistry shifts, unrelated to the skin condition.

Accutane (isotretinoin), for severe cystic acne, has been linked to mood changes, with mandatory monitoring programs in place. Dermatologists screen for depression before prescribing.

• Depression from skin rash treatments: Mood lowering occurs via systemic absorption affecting hormones or inflammation. Topical steroids like hydrocortisone, for eczema or psoriasis, can cause this when used extensively, leading to adrenal suppression. Limiting duration helps.

• Murderous thoughts from malaria drugs: Severe neuropsychiatric effects include violent urges or psychosis. Lariam (mefloquine), for malaria prophylaxis in travelers, disrupts brain signaling, banned for some military uses due to risks.

• Compulsive gambling from antidepressant: Sudden urges to gamble excessively stem from dopamine surges. Abilify (aripiprazole), an adjunct for depression or schizophrenia, overactivates reward centers, leading to lawsuits over undisclosed risks.

• Sleep-driving or eating from sleeping pill: Unconscious behaviors during partial arousal, with no memory afterward.

Ambien causes this by impairing judgment in sleep states, prompting warnings against mixing with alcohol.

• Deja vu sensations from migraine med: Repeated feelings of familiarity without reason, from altered temporal lobe activity. Topiramate, for migraines and seizures, affects neural firing, often dose-dependent.

• Reduced prejudice from beta-blocker?: A curious twist, where implicit biases lessen via fear response dampening. Propranolol, a beta-blocker for hypertension, may reduce subconscious prejudices, per small studies.

• Paranoia from stimulants: Heightened suspicion or delusions from overstimulation. Adderall, for ADHD, can exacerbate this in high doses or misuse.

• Emotional blunting from antidepressants: Feelings become muted, reducing joy alongside sadness. SSRIs like Zoloft flatten emotions for some, impacting relationships.

• Hypersexuality from Parkinson’s drug: Excessive sexual urges or compulsions from dopamine boosts. Requip, for Parkinson's, can lead to risky behaviors, requiring dose tweaks.

41-50: Structural and Connective Tissue Nightmares

• Jawbone problems (osteonecrosis) from bone-strengthening meds: Osteonecrosis of the jaw (ONJ) involves bone death and exposure causing pain and infection.

Bisphosphonates like Fosamax, for osteoporosis to strengthen bones, inhibit bone remodeling, raising ONJ risk in 0.1-1% of users.

• Thighbone breaks (atypical fractures) from bone-strengthening meds: Femur fractures may occur with minimal trauma, from suppressed bone turnover weakening structure.

Long-term Fosamax use paradoxically increases this risk after 5+ years, affecting 1 in 1,000 patients.

• Tendon ruptures from antibiotics: Sudden tears in tendons like the Achilles, from collagen degradation, causing immobility.

Fluoroquinolones like Cipro elevate this risk up to 3.2 times, especially in older adults or steroid users. Black-box warnings advise alternatives.

• Ligament tears from antibiotics: Weakened ligaments snap or tear, leading to joint instability. The same fluoroquinolones damage connective tissue via matrix metalloproteinase inhibition. Recovery involves surgery and rehab.

• Perineum tears or ruptures from antibiotics, steroids, Jardiance, and other meds: Rips in the perineal area (between genitals and anus) from tissue fragility, potentially causing pain or incontinence.

Fluoroquinolones or corticosteroids like prednisone, for inflammation, weaken pelvic floor collagen. Reports link to broader connective tissue toxicity. This side effect is also reported with Jardiance for diabetes, blood thinners, and hormone therapy.

• Joint dislocations from steroids: Joints become loose and dislocate easily from eroded cartilage. Corticosteroids for arthritis accelerate breakdown over time.

• Muscle wasting from statins: Atrophy reduces muscle mass and strength. Statins like Lipitor, for cholesterol, cause myopathy in 10-15% via mitochondrial damage. They may also cause the potentially fatal kidney disorder rhabdomyalosis and brain issues.

• Bone density loss from acid reflux meds: Weakened bones from impaired calcium absorption increase fracture risk. Proton pump inhibitors like Nexium, for acid reflux, when used long-term, raise osteoporosis odds.

• Tardive dyskinesia from antipsychotics: Involuntary facial movements like grimacing from dopamine receptor changes. Antipsychotics like Haldol cause this in 20-50% long-term users.

• Chronic fatigue from birth control pills: Persistent exhaustion not relieved by rest, from hormonal disruptions. Birth control pills alter estrogen/progesterone, affecting energy in some women.

These eye-opening examples show how medicines, while targeting one issue, can cascade into unrelated chaos—sometimes irreversibly.

The body's interconnected web means no drug acts in isolation.