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5 Unexpected Side Effects of Common Medications

Some popular drugs may spark odd, unexpected reactions, like color blindness, deja vu and even compulsive gambling

By Linda Melone | August 6, 2013

Even the most-studied, widely prescribed drugs can have unwanted side effects, like stomach upset, drowsiness and fatigue. It's the price we pay to address more serious medical issues. Some medications, though, can cause unexpected and unusual side effects very different than those listed at the top of the box or pamphlet, says pharmacist Suzy Cohen, author of Drug Muggers: What Medications Are Robbing Your Body of Essential Nutrients and How to Restore Them.

Below, we list some of these unexpected side effects and suggest alternatives for those who might experience them. They are generally rare and non-life-threatening, but speak to your doctor or pharmacist and read consumer advisories for all your prescriptions to learn more.

(MORE: 7 Questions to Ask About Every New Prescription)

"If you need a medication for a life-threatening infection or a progressive, disabling disease," Cohen says, "consider that and don't just deny yourself medication because of a rare side effect. The odds are you are not going to suffer a bizarre side effect, especially if you start at lower dosages and test the waters before diving in head first."

Drug: Ambien
Unexpected side effect: sleep driving or eating

Like sleepwalking, sleep driving involves driving somewhere with no memory of the activity. Within a few days of starting to take this widely used sleep aid to treat insomnia, some people will sleep drive, carry on complex conversations, perform routine daily tasks, have sex or eat while asleep, with no memory of the experiences.

The behaviors often occur in the morning, because Ambien remains in your bloodstream even after you wake, says Zara Risoldi Cochrane, an assistant professor of pharmacy practice at Creighton University in Omaha, Neb. "For some people, these blood levels are high enough to cause carryover effects," she says, including, in some cases, sleep driving.

The rate of occurrence has not been measured, but it is believed to be rare. "The FDA has received about 700 reports of sleep driving in the 20 years since Ambien was approved," Cochrane says

"The changes are different in women and men," Dr. Ellis Unger of the Food and Drug Administration's Office of Drug Evaluation recently told ABCNews.com. "We don't understand why yet, but women are more susceptible to next-morning impairment." In January, the agency advised doctors to reduce the prescribed dose of Ambien for women from 10 mg to 5, and from 12.5 mg to 6.25 mg for extended-release products like Ambien CR. As an alternative, you could consider over-the-counter sleep aids or ask your doctor about adjusting your Ambien dosage.
 
Drug: Lorazepam
Unexpected side effect: déjà vu
 
Fewer than 5 percent of people who take this anti-anxiety medication or others in the class of drugs known as benzodiazepines — like Xanax, Librium, Tranxene and Valium— will experience this odd effect, Cohen says.

This form of déjà vu, however, is not exactly what you'd expect. "It's not the feeling that you've done this before or been here before," Cohen says. "It's more like a feeling that is hard to put your finger on, like a flashback to a certain time or place. Maybe you suddenly imagine or dream you are back in your childhood, for example." (This effect has also been linked, in rare cases, to the antiviral medication amantadine.)

The cause is unclear. "Epilepsy, anxiety and other psychiatric disorders are associated with déjà vu," Cochrane says, "suggesting that this effect may sometimes be a symptom of an underlying disease rather than a drug side effect." Taking lorazepam in conjunction with drugs that affect neurotransmitters such as dopamine may bring on or intensify the effect.
 
If you experience déjà vu, talk to your doctor about switching to a different class of anti-anxiety drugs or consider natural anti-anxiety herbs, like Valerian root, passionflower, hops or glycine powder.
 
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Drugs: Requip and Mirapex
Unexpected side effect: compulsive gambling

Requip and Mirapex are prescribed to treat Parkinson's disease symptoms, as well as restless leg syndrome and leg cramps. They work by activating dopamine receptors in people who have a shortage of the neurotransmitter, which influences both movement and mood. But for 5 to 10 percent of users, the increased dopamine effect can spur unexpected and unwanted reactions.

"Too much dopamine turns on our pleasure center," Cohen says. "This 'passion' hormone causes uncontrollable urges like gambling and having sex and is most often seen in young males." If this happens to you, Cohen advises, talk to your doctor about switching to natural remedies or supplements to treat leg cramps or restless leg syndrome, including folate, iron and magnesium. If you've been taking Requip to address Parkinson's symptoms, she says, your physician may be able to switch you to a drug such as Sinemet.
 
Drug: Viagra
Unexpected side effect: color blindness
 
Its commercials are so widely aired that many of us may be able to recite the popular erectile-dysfunction drug's most common side effects by heart. But most users are unaware that in rare cases, it can also cause a type of color blindness, usually involving a difficulty distinguishing blue and green. The effect is usually temporary, although in isolated incidents, the drug has caused brief or long-term total vision loss. The effect appears to be caused by an interruption of blood flow to the optic nerve.

If you experience this effect, you should look into one of several natural treatments for improved sexual function, including yohimbe, maca root and ginseng. "Viagra and similar drugs are just short-term fixes," Cohen says. "They do nothing for the underlying cause, which is usually testosterone deficiency." If you discover that you or your partner has testosterone deficiency, she says, "Drug therapy such as testosterone replacement would be ideal in terms of a long-term solution."

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Drug: Dapsone
Unexpected side effect: carbon monoxide poisoning symptoms

This antibiotic is often taken by people with compromised immune systems – including HIV patients and those with leprosy or skin conditions – to prevent infections. But 1 to 5 percent of users may experience a scary and disturbing disorder known as acquired methemoglobinemia, which involves breathing difficulty, cyanosis (gray or blue skin), abnormal heart rhythm, chest pain and weakness. These symptoms are typical of carbon-monoxide poisoning. The big difference: There's no carbon monoxide involved and the effect is not life-threatening. 

In methemoglobinemia, Cohen explains, red blood cells contain methemoglobin (a form of hemoglobin) at levels higher than 1 percent. This elevated level of methemoglobin can prevent hemoglobin from releasing oxygen effectively to body tissues. Severe episodes may require treatment, including a blood transfusion. But in most cases of acquired methemoglobinemia, no action needs to be taken, except to cease using the drug, according to the National Institutes of Health. Alternative medications include Bactrim DS or Mepron, which have a lower risk of this rare condition.