Like HowStuffWorks on Facebook!

Top 10 Weirdest Prescription Drug Side Effects

        Health | Medications

Weird Side Effect 5: Strange Sleep Behaviors

It's hard to see the road when your eyes are shut.
It's hard to see the road when your eyes are shut.
Adam Gault/Digital Vision/Getty Images

We all have weird dreams at times, right? Some prescription drugs give patients disturbing dreams every time they go to sleep, and others can actually cause users to sleepwalk and behave violently while asleep. One of the lesser side effects of Chantix (generic name varenicline), a prescription drug designed to help people stop smoking, is nightmares and night terrors. Night terrors aren't just scary dreams; people who experience them are struck by fear and partially awaken out of sleep, sometimes screaming or moaning. They don't usually wake up completely, and they don't always remember that the incident even happened.

Some drugs with this side effect are directly related to sleeping; that is, they're designed to help people with chronic insomnia. Lunesta (generic name eszopiclone) is a hypnotic drug -- meaning, it induces sleep -- prescribed for sleeplessness with directions to take on an "as needed" basis. But its users, as well as those of Ambien (generic name zolpidem), have also reported night terrors and nightmares. Both Lunesta and Ambien patients, though, have experienced an even weirder effect: performing activities in their sleep.

­These activities include not only sleepwalking, but eating, making phone calls, having sex and driving -- yes, driving. Patients taking these sleep aids have woken up while backing their cars out of driveways or while shopping at all-night grocery stores. Some "Ambien drivers" have been arrested for driving while impaired and causing accidents [source: CBC News]. Both drugs' makers include warnings about these side effects and emphasize that they shouldn't be taken with alcohol (which can exacerbate the effect).

Check out number four on our list. It isn't just a weird side effect -- it's outright disgusting.