10 Worst Prescription Drug Side Effects

Thanks to our reader, Jennifer B., for the idea!


Although total amnesia is incredibly rare, some prescription drugs can also cause amnesia. This is the case for some users of Mirapex (generic name pramipexole). Mirapex was developed in 1997 to control the symptoms of Parkinson's disease and is also prescribed for people with Restless Leg Syndrome (RLS). This medicine has several side effects, one of them is amnesia. Some patients reported short-term memory loss, such as not remembering what they did the day before. Going off Mirapex seemed to get rid of the problem. This side effect can also happen with patients who take statins, a class of drugs that are supposed to lower cholesterol. Duane Graveline, a former astronaut, reported coming back from a short walk and not recognizing his wife while he was taking Lipitor. Then he lost memories of any events beyond his high school graduation.

2Enlarged Breasts (in men, sorry girls)

A hair loss cure on the market has a unique side effect, in that it can cause "gynecomastia". What does this mean? It means the ability to grow lactating breasts. However, this disturbing side effect can be stopped by ceasing the intake of the medication. PROPECIA, for example, was developed to treat mild to moderate male pattern hair loss on the top of head and middle front of head in men only. It has been shown that the drug for propecia, Finasteride, increases both testosterone and estrogen while lowering serum levels of DHT. The increase in estrogen creates a side effect called gynecomastia, or breast enlargement, in some men, along with increased body fat and loss of libido.


Unless you are planning to kill yourself with pills overdose, the least thing you would expect from a medicine to cause you is death. But for patients with arthritis, that's a risk they may face while taking Celebrex. According to the product web page, Celebrex may increase the chance of a heart attack or stroke that can lead to death. Serious skin reactions or stomach and intestine problems, such as bleeding and ulcers, can occur without warning and may cause death.

4Decrease in Balls' Size

Testosterone replacement therapy is used in patients who suffer from low testosterone levels. This therapy can resolve the effects of hormonal imbalance, but not without the possibility of side effects. While going under treatment, men should be aware of a ‘tiny' possible effect, such as a decrease in their testicles size. Younger men may also experience decreased sperm counts while on testosterone replacement therapy. This can result in decreased fertility.

5Cancer, Stroke, Dementia and Much More

One drug on the market, EvaMist -- a treatment for menopause symptoms such as hot flashes -- has possible side effects that include cancer, stroke, heart attack, blood clots, and dementia!


Are you trying to quit smoking? There is a drug that can help you do that. The only problem is that it can also make you want to kill yourself. The good thing is that you are not going to smoke anymore if you are dead, right?. That's the case of Chantix: "Some patients have reported changes in behavior, agitation, depressed mood, suicidal thoughts or actions when attempting to quit smoking while taking CHANTIX or after stopping Chantix." Smoking can kill you, but trying to stop can be deadly as well.


You might expect to see or hear something that isn't actually there if you were taking an illegal drug like LSD or even a heavy painkiller like morphine. However, some of the most unlikely prescription drugs "may cause visual and auditory hallucinations" as one of their side effects and it's probably not the ones that you'd expect. Lariam (generic name mefloquine) was invented by researchers at the Walter Reed Army Institute of Research to prevent and treat outbreaks of malaria in the U.S. Army. Until recently, it was given routinely to soldiers deployed overseas as well as many tourists. Lariam carries some serious side effects -- one of them being hallucinations. Both soldiers and tourists have reported experiencing frightening hallucinations as well as violent psychotic behavior soon after taking the drug. Since the early 2000s, the FDA has required that patients be screened for a history of depression and psychosis before taking Lariam.

8Loss of Sense of Taste (and other senses)

Have you ever swallowed a pill and been left with a nasty taste in your mouth, especially if you didn't drink water immediately afterward? Unless they're meant to be chewed or dissolved, most pills don't taste all that great. But some pills don't just leave a bad taste -- they can completely distort your sense of taste. And taste isn't the only sense that can be affected by pills' side effects. Vasotec (generic name enalapril) is a drug designed to treat high blood pressure and congestive heart failure. However, it can affect almost all of your five senses. Vasotec can cause you to lose your sense of smell (a condition known as anosmia) and taste, as well as have ringing in your ears (tinnitus) and eye problems like blurred vision and dry eyes. All of these are referred to as minor side effects, but if you were experiencing them all at once, you might consider them major.

9Coughing up blood or vomit that looks like coffee grounds

PLAVIX is proven to help protect against future heart attack or stroke by helping keep platelets in the blood from sticking together and forming clots. This sounds nice until you get to the part that you can vomit blood like coffee grounds. According to the product web page, Plavix is generally well-tolerated, but it is not for everyone. Because of its drug action, clopidogrel can make it easier for you to bleed, even from a minor injury. You may also have bleeding in the inside of your body, such as in your stomach or intestines. Don't worry, you are definitely going to know you have an internal bleeding if you start coughing up blood or vomit that looks like coffee grounds. If that happens, it's time to call your doctor.


If you are diabetic and are taking Avandia to control your blood sugar, don't forget to play safe sex. Besides the fact that this medication can cause or worsen heart failure, women taking Avandia should know that this medicine may increase the risk of pregnancy.