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View Frightful (But Dead Serious) Drug Side Effects

Medically reviewed by L. Anderson, PharmD. Last updated on Oct 10, 2019.

Black Hairy Tongue

Halloween or Mardi Gras costume gone wild? No, it's a condition termed "black hairy tongue". The odd, dark growth on the tongue is due to a bacterial or yeast overgrowth in the mouth. Culprits may be:

Although it may be unpleasant, black hairy tongue doesn't usually require medical treatment; it's temporary and harmless. Be sure to practice good oral hygiene and brush your tongue and teeth twice a day. Talk to your doctor to see if any of your medications may be the cause.

Vanishing Fingerprints

Sherlock Holmes you may not be, but hand–foot syndrome, known by the medical term palmar-plantar erythrodysesthesia, is something to watch out for.

Hand-foot syndrome may occur when cancer treatment affects the growth of skin cells or blood vessels in the hands and feet. Redness, swelling, loss of fingerprints, and pain have been reported.

Cancer drugs cited to cause this effect include:

although it can happen with others. If you develop hand-foot syndrome, talk to your doctor; there are ways to manage it and prevent it from worsening.

Osteonecrosis of the Jaw

Osteonecrosis of the jaw (ONJ) occurs when the jaw bone is exposed and begins to die from a lack of blood. The name of the condition is descriptive - osteo meaning bone and necrosis meaning death. Several drugs are linked with ONJ, including antiresorptive therapies that are ironically used to help prevent the loss of bone mass in diseases such as osteoporosis.

Drugs such as:

can lead to ONJ; however, ONJ may also occur without any identifiable risk factors. Most cases of ONJ happen after a dental extraction in patients taking these drugs.

Compulsive Behaviors

Shopaholic? It might not be so far fetched with the use of some medications. In patients with the movement disorder Parkinson's Disease (PD), dopamine agonist drugs are often used to help stimulate dopamine receptors; examples include:

Clinical studies have found dopamine agonist treatment in PD is associated with 2 to 3.5-fold risk of having an impulse control disorder (ICD) such as compulsive gambling, compulsive buying, compulsive sexual behaviors, or binge-eating disorder.

Some case reports also suggest that ICD may occur with dopamine agonist treatment in patients with restless leg syndrome or fibromyalgia.

Amnesia and Memory Problems

Fuzzy memory and forgetfulness is not just a sign of old age. Several drugs are associated with forgetfulness, or flat out amnesia.

All can cause memory loss. Some medicines such as midazolam (Versed), also a BZD, are used to purposely induce sedation and memory loss of medical procedures.

The amnesia or forgetfulness is usually short-lived and disappears once the drug wears off; however, the events that occurred while the patient was under the effect are usually forgotten.

Nightmares or Night Terrors

If you have ever woken up from a dream in a cold sweat, you know a nightmare or night terror is a horrific event. Many medications, especially those that might work in the brain, can cause abnormal or vivid dreams. For example, medications used to help patients quit smoking can cause nightmares:

However, some smoking cessation studies have shown that after 12 weeks of use, close to half of users were able to quit smoking, so check with your doctor. You might be able to lower your dose to help with the dream side effect.

And don't forget, the serious side effects from smoking - chronic lung disease like COPD, lung cancer and possible death - is permanent.

Dysgeusia (Abnormal Tastes)

That latest bad taste in your mouth might not just be from the cost of your prescription.

Dysgeusia is a condition that affects the ability to taste or results in an odd taste. For example, some drugs cause a distorted sense of taste:

  • Metronidazole (Flagyl) is used to treat bacterial infections, but a common side effect is a distinct metallic taste in the mouth that can make treatment intolerable.
  • Taste changes can be frequent among senior patients who take multiple medications, as well.
  • Captopril for blood pressure control, the antibiotic clarithromycin (Biaxin XL), and multivitamins, especially those containing metals like calcium or iron, can cause a metallic taste, too.

Certain chemotherapy and anesthesia medications can do this, also.

Bizarre Sleep-Related Behaviors

"Things That Go Bump in the Night" just took on a new meaning.

Those who take prescription sleep aids such as:

have been known to get up at night and go for a drive, take a walk, chat on the phone, binge eat, or even have sex -- and not remember any of it in the morning.

Do not drink alcohol or take medicines that can make you drowsy, which can worsen these side effects. It is extremely important to follow dosing instructions for these medications, and be sure you have adequate time to devote to sleep before you must get up.

These behaviors may be due to alterations in brain neurotransmitters, but the exact cause is not fully known.

Don't It Make My Brown Eyes Blue

You've heard of that little blue pill?

It's sildenafil (Viagra), the popular erectile dysfunction (ED) drug. There have been reports of Viagra causing a bluish tint (cyanopsia) to vision in about 3 out of every 100 men.

Viagra and related drugs like

work by inhibiting phosphodiesterase 5 (PDE5) to facilitate erections.

According to the drug maker, the visual blue hue is due to a blockage of another PDE enzyme present on the retinal photoreceptor. The blue vision is temporary; long-term side effects are unknown. Rarely, vision loss and double vision may also occur with higher doses of PDE5 blockers in men with certain risk factors.

Colored Urine?

Face-painting is fun - but colored urine?

Some drugs can lead to odd and alarming urine colors. For example

are all drugs that can lead to blue or green urine.

Rifampin, an antibiotic used in the treatment of tuberculosis, can turn urine a reddish-orange. The urinary tract analgesic phenazopyridine and the laxative senna can also cause an orange-reddish urine.

Urine discoloration due to these medications is not a serious problem and will clear once the drug is out of the system. More seriously, pink or red urine can be caused by blood from conditions such as urinary tract infections, enlarged prostate, tumors or kidney stones. See your doctor immediatley about that one.


Bells ringing in the belfry are a familiar sound on Sunday, but if you continue to hear this sound day after day, you may have tinnitus.

Tinnitus is a hearing sensation that is often described as a ringing in the ears. Hearing loss due to age or medication side effects can lead to tinnitus. These drug examples can all cause the side effect of tinnitus.

Fortunately, once the medication is stopped, the ringing usually goes away; however, contact your doctor before you abruptly discontinue any regularly-prescribed medication or antibiotic.

Can't You Smell That Smell?

The loss of smell, also known as anosmia, can be a real problem for some holidays. But on Turkey Day, it's important to have all of your olfactory parts in working order, don't you agree?

Enalapril (Vasotec), a blood pressure medicine, has been rarely associated with anosmia. Other medications that have been linked with loss of smell include:

The loss of smell can sometimes be linked with a serious condition, such as Parkinsons disease, but it isn't always serious in and of itself. Nonetheless, you need to be able to smell to fully taste and enjoy foods.


Hallucinations occur when sensing or seeing things that appear to be real, but have only been created by the mind. Hallucinations are a serious side effect and require a thorough medical investigation. Not all hallucinations are linked to psychiatric disorders or drug abuse.

Common hallucinations may include: crawling bugs, hearing sounds or voices, or seeing lights. Hallucinations may occur with conditions such as schizophrenia or dementia.

Examples of prescription drugs that may trigger a hallucination include:

Illicit drugs that can lead to hallucinations include:


This might be the most fearful side effect of all, and for good reason.

Priapism is a prolonged, painful erection of the penis. The erection is not due to sexual stimulation, but may be the side effect of a drug.

Priapism is an uncommon side effect, but if a prolonged erection lasts for longer than 4 hours, seek emergency medical care immediately.

Drugs that have been implicated in leading to priapism include:


Vertigo is the name of the famous Alfred Hitchcock psychological thriller - and it's also the term given to the extreme dizziness that creates the sense that you or your surroundings are spinning or moving while you are actually at a standstill. Whoa.

Toxic levels of anti-seizure drugs such as:

have been reported to cause vertigo.

Antibacterial aminoglycoside drugs like gentamicin can be toxic directly to the ear and result in vertigo.

Drugs to control high blood pressure such as the water pill furosemide (Lasix), the antimalarial agent mefloquine, and not surprisingly, excessive alcohol consumption have also been linked to vertigo.


Gynecomastia is breast enlargement in men due to hormonal imbalances, not excess growth of fat tissue. Some drugs are known for causing gynecomastia due to effects on hormones. For example, gynecomastia and impotence have been reported in patients receiving prolactin-elevating compounds.

The condition is reversible in about 80% of cases; however, gynecomastia can cause extreme anxiety and embarrassment.


Vampires usually hide from the sunlight. Unfortunately, some medicines may keep you out of the sun, too. Drugs that cause photosensitivity reactions - such as:

may cause an increased skin sensitivity to sunlight or artificial light. The drug absorbs the UV light from the sun and leads to a skin reaction like a rash or blisters.

Not everyone who takes an offending drug will develop a photosensitivity reaction, and it may take 1 or 2 days for the reaction to develop. Contact your doctor if you should develop a unusual skin reaction after taking any medicine.

Those Creepy Added Pounds

Weight gain is also one of the most dreaded drug side effects. Let's face it - keeping weight off is a hard enough task without gaining weight from medications. Aging, lack of exercise, and frightful eating habits are all culprits in the battle to keep weight down.

However, some common medications can also lead to weight gain - drugs used for:

can all add on unwanted pounds. Ask your doctor about this side effect. You may be able to switch to a different medication or use a lower dose if one of your meds put you at risk for weight gain.

And remember, medications may affect patients differently, so not every patient will gain weight.

Drug Side Effects are Really No Laughing Matter

So there you have it, some of the top unusual drug side effects. No doubt, some are downright chilling, but this highlights the need to adequately research your drug side effects before you start taking them.

Ask questions, too, when your doctor prescribes a medication:

  • What are the most common or serious side effects you can expect to see?
  • What side effects should you call the doctor about?
  • How often do they occur?
  • Are there any rare side effects you should be aware of?
  • Are there other treatment options if side effects become to bothersome?

Most importantly, do not stop taking any medication without first talking to your doctor - they may be able to prescribe a lower dose or alternative drug.

And many drugs need to be stopped slowly - quickly stopping a medication may lead to even more scary side effects - just exactly what you were trying to get away from!

Finished: View Frightful (But Dead Serious) Drug Side Effects


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  • Weintraub, D, et al. Impulse control disorders in Parkinson's disease. A cross-sectional study of 3090 patients. JAMA Neurology 2010;67:589-95. Accessed 10/10/2019
  • Vision Web. Viagra and Vision. Accessed 10/10/2019.
  • Mayo Clinic. Diseases and Conditions. Black Hairy Tongue. Causes. Accessed 10/10/2019 at
  • Thompson DF, Kessler TL. Drug-Induced Black Hairy Tongue. Pharmacotherapy. 2010;30:585-93. Accessed 10/10/2019.
  • Hand-Foot Syndrome or Palmar-Plantar Erythrodysesthesia. Accessed 10/10/2019 at
  • Harmon K. Scientific American. Can You Lose Your Fingerprints? Accessed 10/10/2019.
  • Mayo Clinic. Urine Color. Causes. Accessed 10/10/2019 at
  • Vasotec. Product Labeling. Valient. Accessed 10/10/2019
  • MedLine Plus. Smell - Impaired. Accessed 10/10/2019 at
  • Viagra. Product Labeling. Pfizer. Accessed 10/10/2019 at
  • Mayo Clinic. Tinnitus. Causes. Accessed 10/10/2019 at
  • FDA. FDA Advises Consumers Not To Use Certain Zicam Cold Remedies Intranasal Zinc Product Linked to Loss of Sense of Smell. Accessed 10/10/2019
  • MedLine Plus. Hallucinations. Accessed 10/31/2018 at
  • Family Practice Notebook. Vertigo Caused by Medication. Accessed 10/10/2019 at

Further information

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