Antihistamines are an allergy sufferer's best friend. But be warned: If you drive while taking antihistamines, that over-the-counter pal could leave you at risk for a traffic ticket -- or worse.
Antihistamines aren't the only medicines that can jeopardize your "good driver" discount. Doctors say several over-the-counter and prescription medicines can impair your judgment behind the wheel.
"Some medicines can slow your reflexes, produce temporary confusion or 'brain fog' or leave you feeling terribly groggy," says Dr. Stacey Weiland, an internist in York, Pa.
A foggy mind and sluggish reflexes might cause you to forget to look both ways while making a turn or to fly past stop signs without noticing them.
"Several studies have shown certain medicines significantly increase the chance of getting into a crash," Weiland says. "Depending on the drug, you could be up to 10 times or more likely to crash."
Use good judgment
Auto insurance applications don't ask you to disclose what medicines you're taking, so it's up to you to know how certain drugs affect you and whether you should be behind the wheel.
State Farm agent Sarah Holtrup says car insurance companies can ask customers to pay more -- or choose to not renew their policies -- if the driver's medication history factors into reported crashes or traffic tickets.
Driving under the influence of medications could result in lawsuits as well.
"Knowingly driving while taking medications that impair your judgment or reflexes raises the liability stakes, and could have you facing gross negligence or punitive damages if you're involved in an accident," says Frank Darras, an insurance attorney in Ontario, Calif.
Here's a look at some medications that could affect your performance behind the wheel.
• Allergy medicines. Benadryl, chlorpheniramine (Chlor-Trimeton), clemastine (Dayhist), hydroxyzine (Atarax) and even some of the second-generation antihistamines, like Zyrtec, can cause drowsiness or sedation, says Lori Helke, a clinical pharmacist at Optima Health in Virginia Beach, Va.
"If the label states that the medication is an antihistamine, you should read the warnings and precautions concerning driving carefully," says Helke, who explains that antihistamines are used to suppress histamine-induced responses, such as a runny nose and watery eyes. "Unfortunately, we also have histamine receptors in other parts of our bodies -- like our central nervous system and small intestine -- which is why antihistamines can cause you to become sleepy."
According to Helke, immediate-release antihistamines may cause drowsiness for only a few hours, but some of longer-acting or extended-release products can affect your central nervous system much longer.
"Even some 'non-drowsy' formulas can cause some drowsiness," Los Angeles internist Dr. Gregory Smith says.
• Cough and cold medicines. Over-the-counter cold medicines like NyQuil can cause a hangover-like effect in some people, making them feel tired or sluggish for up to eight hours. That's why Smith says you shouldn't drive for at least 12 hours after taking this type of medicine, "just to be safe."
According to Helke, cough medicines that contain dextromethorphan (the "DM" in cough medication) can cause drowsiness, blurred vision and even confusion. At recommended doses, dextromethorphan can cause mild depression of the central nervous system, leading to slight dizziness or drowsiness, says Helke, noting that cough syrups often contain alcohol, too.
"That added alcohol effect could make driving hazardous because you've got two things that impair your sense and mental abilities," Helke says.
Like allergy medicines, the drowsy effects of cough and cold medicines can kick in as soon as 15 to 30 minutes after they're taken.
• Diarrhea medicines. Loperamide is an "opioid receptor agonist" that affects the intestines. Drowsiness and dizziness are rare, but those symptoms can happen within one to three hours of taking an anti-diarrheal. Drowsiness can last up to eight hours.
If you're going to be driving, Helke says, Kaopectate or Pepto-Bismol are safer choices because they may not cause drowsiness.
• Narcotic painkillers. These medications can numb your pain, but they also can dull your ability to react quickly if a dog, child or car darts into your path. Weiland says painkillers also impair your judgment of when and how hard to apply your car's brakes.
"An hour or less after taking them, painkillers can also make you very sleepy," Weiland says
• Sleeping pills. You probably wouldn't take one right before you're about to drive, because sleeping pills are designed to, well, help you fall asleep. But Weiland says you still could feel the effect many hours later.
"Some people feel groggy eight to 10 hours or more after taking a sleeping pill," says Weiland, suggesting that individuals hold off on driving for at least 12 hours after taking a sleeping pill.
• Antidepressants and anxiety medication. These prescriptions may make you feel "loopy," confused or forgetful, according to Weiland, who notes that several studies have shown an increased risk of traffic accidents in both elderly and young drivers taking antidepressants. "They're very sedating," Smith says.
• Muscle relaxants. Because they suppress your central nervous system, the same drugs that send lower back pain packing can leave you more than three times as likely to be in a crash, according to Weiland. Muscle relaxants can trigger slower reactions and inhibit your ability to make critical decisions quickly, she says.
• Attention deficit drugs. If you're taking medicine for any type of attention disorder, talk to your doctor about potential side effects that may reduce your ability to drive safely. "These can cause confusion and drowsiness in some people, and hyperactivity in others," Smith says.