10 Bizarre Side Effects of Common Medications

Updated: Jan. 10, 2019

Blue urine? Weight gain? A hairy tongue?! Watch out for the strange things that can happen when you take certain drugs.

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You won’t believe what your meds can do

You know that some medications can cause drowsiness, headaches, and nausea. But the fine print on your Rx package might also mention some unusual and downright wacky side effects you’ve never heard of—and that your doctor may not have mentioned to you. We spoke to a pharmacist about ten of the more bizarre possibilities so you’ll be better prepared next time you fill a prescription.

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Urine color changes—including blue

A number of medications can change the color of your urine, says Dave Walker, RPh, a pharmacist and medical advisory board member for MedShadow. “The classic urine change medication is Pyridium, used to lessen the discomfort experienced during an active urinary tract infection. This will change the urine orange to red depending on the acidity of the urine, he says. Tuberculosis drug rifampin, anti-inflammatory sulfasalazine, and blood thinner warfarin can also cause orange urine. The antibiotics nitrofurantoin and metronidazole can lead to brown urine, and commonly prescribed meds like amitriptyline, doxorubicin, indomethacin, cimetidine, Phenergan, and triamterene can cause blue or green urine. “If you notice something that looks different or weird, consult your physician or pharmacist,” Walker says. Read about 17 everyday medication mistakes that could be making you sick.

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Changes in sexual arousal

Top among the drugs that may decrease or suppress sexual arousal and performance, says Walker, are the selective serotonin reuptake inhibitors (SSRIs) Paxil, Celexa, and Zoloft; certain blood pressure medications; and hormones including birth control pills. Erectile dysfunction drugs like Viagra can cause persistent and painful erections, but so can the antidepressant trazodone (Oleptro).

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Addictive behavior

Drugs for restless legs disease and Parkinson’s—Mirapex (pramipexole) and Requip (ropinirole)—can lead to compulsive behavior, says Walker. This could include gambling, sexual addiction, compulsive shopping, binge eating, and other types of eating disorders. In lawsuits, people have claimed that Abilify, an antipsychotic drug prescribed for depression and bipolar disorder, has triggered compulsive behavior—particularly gambling. Find out the 49 secrets your pharmacist isn’t telling you.

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Some drugs have caused people to sleepwalk or even sleep drive. They may also fall asleep suddenly in the middle of the day. “Different people will react differently to medications that affect the central nervous system,” Walker says. “Anti-anxiety medications including benzodiazepines and sleep medications like Ambien, Lunesta, and Sonata are often the culprits.” Opioid pain medications, muscle relaxants, and even over-the-counter antihistamines like Benadryl may cause these effects in some people, he adds.

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Loss of smell and taste

“A number of antibiotics may cause changes in sense of taste or smell,” Walker says. These include ampicillin, macrolides, quinolones, sulfamethoxazole, trimethoprim, tetracycline, and metronidazole. According to a study in Canadian Family Physician, neurologic meds including antiparkinsonians, CNS stimulants, migraine medications, and muscle relaxants can have a similar effect, as can cardiac drugs (antihypertensives, diuretics, statins, and antiarrhythmics) and most thyroid meds. Other culprits include tricyclic antidepressants, some antipsychotics, anxiolytics, mood stabilizers, hypnotics, antihistamines, bronchodilators, anti-inflammatories, stop-smoking aids, antifungals, and antivirals. Check out the 15 things your pharmacist wishes you knew.

Spider on the wall


A wide range of meds that affect the central nervous system can cause this side effect. “I had a family member who would see spiders on the wall after receiving morphine,” Walker says. Drugs used to treat pain and ease anxiety and depression can also cause hallucinations, as can anticholinergic drugs used to treat bladder conditions, chronic obstructive pulmonary disease, and Parkinson’s. “Mirapex (pramipexole), used for Parkinson’s and restless legs syndrome, is also implicated, especially in the elderly,” Walker says.

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Extreme weight gain

An estimated 10 to 15 percent of weight problems may be related to medications. Some drugs increase hunger while others interfere with the body’s ability to burn calories or cause patients to retain fluids. Some common medications associated with weight gain include corticosteroids, tricyclic antidepressants, SSRIs like Prozac, Celexa, and Paxil, and sulfonylureas used to treat type 2 diabetes, says Walker. Make sure you know the 10 medication mistakes that might be hurting your health. 

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Visual disturbances

Certain medications can affect your eyes in ways ranging from blurred vision to retina damage. These drugs include erectile dysfunction drugs, blood pressure medications, minocycline, and other antibiotics, and even some herbal medications, says Walker. Corticosteroids, antipsychotics, antimalarial meds, and antihistamines can also cause vision problems.

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Tendon ruptures

“The most frequently heard-about medications causing tendinitis or ruptured tendons are the drugs of the fluoroquinolone class, including Cipro, Cipro XR, Proquin XR, Levaquin, Floxin, and their generic equivalents,” says Walker. Drug-induced ruptures have occurred in the Achilles tendon, the rotator cuff, the biceps, the hand, and the thumb. Make sure you know to ask these questions before taking prescription medication

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Black hairy tongue

“This side effect was always a fun topic in pharmacy school,” says Walker. “Thought to be a change in the normal bacteria of the mouth, it can be caused by taking some antibiotics.” Other causes of this unpleasant side effect include poor oral hygiene, smoking, excessive coffee drinking, and dehydration. Products containing bismuth, such as Pepto-Bismol, may also cause it, Walker says. Next, make sure you know the signs you’re taking too many prescriptions.