Certain medications, including Benadryl, can have the side effect of drowsiness. This can have a big effect on your daily life. But there are methods to help manage this tiredness.
You expect to feel tired if you take sleeping pills. But when other medications make you sleepy, it can interfere with your life.
“Many medicines can have this side effect,” says Barb Hergert, PharmD, a clinical pharmacist in Optum’s Clinical Engagement Services Center.
Among the medications likely to cause drowsiness, antihistamines are among the most common. This includes over-the-counter brands you might be familiar with, including Benadryl and Zyrtec.
Some other medications that might cause sleepiness include:
antianxiety medications
antidepressants
antipsychotic medications
antiseizure medications
beta-blockers
muscle relaxers
opioids
In some cases, you may not even realize that your medication is responsible for your drowsiness. But knowing more about the medications that cause it and ways to counteract it can help you manage drowsiness while you manage your health.
Why do some medications make you drowsy?
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The reason some medications make you sleepy depends on the type of medication. For example, drugs that slow your heart rate, such as benzodiazepines, can have a relaxing or sedative effect on your body, which can lead to drowsiness.
According to Hergert, “Everyone reacts to medicines differently, so it’s hard to generalize. But let’s use beta-blockers as an example. They lower your heart rate, which could leave you feeling a little tired.
Antihistamines, on the other hand, work differently. People with seasonal allergies often take them to block histamine. This is a chemical your body makes, and it’s responsible for allergic reactions such as congestion, sneezing, and itchy eyes.
But histamines also work on the brain. They block receptors that regulate sleep and wakefulness. So when you take an antihistamine to get relief from your allergies, it may also affect your sleep cycle.”
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What should I do when I realize that a new medication is making me drowsy?
Hergert says, “If you’re just starting on a medication that’s known to cause drowsiness, avoid doing activities that require alertness — such as driving — until you know how it affects you. Then give it a few weeks. Your body may adjust to the medication, and you’ll start to feel less drowsy.”
What if some time goes by and I still feel drowsy?
According to Hergert, “If you feel you aren’t adjusting to your medication, reach out to your doctor. He or she may be able to recommend ways to reduce or eliminate the drowsiness. For instance, it may be that the dose or the time of day you take the medication should be adjusted.
In some cases, your doctor may recommend a different medication. Just be sure you make this decision with your doctor’s help. You shouldn’t make these kinds of changes on your own.”
What should I do if my antihistamine is making me drowsy?
Antihistamines may be first-generation antihistamines or second-generation ones. First-generation antihistamines are more likely to cross the blood–brain barrier, meaning they directly affect the brain and the central nervous system, making drowsiness more likely.
Hergert says, “Older, first-generation antihistamines are more likely to cause drowsiness. These include diphenhydramine (Benadryl), chlorpheniramine (Chlor-Trimeton), and hydroxyzine (Vistaril).
If you take one of these medications, consider taking it at bedtime. Alternatively, you can talk to your doctor about switching. Newer, second-generation antihistamines are less likely to cause drowsiness. These include fexofenadine (Allegra), loratadine (Claritin), and cetirizine (Zyrtec).”
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Fatigue is a commonly experienced side effect of beta blockers like labetalol (Trandate) and acebutelol (Sectral). This is likely due to its effect on your heart rate and how it affects the release of hormones in your body.
Hergert says, “In addition to slowing your heart rate, beta-blockers also relieve pressure on the heart by blocking the action of certain hormones, such as adrenaline. And when you have less adrenaline, you may have less energy.
Most people can tolerate beta-blockers. But a small percentage may experience some drowsiness and fatigue.”
Should I stop taking the beta-blocker if I’m drowsy?
According to Hergert, “No. Don’t stop on your own. Tell your doctor if you’re feeling fatigued and it’s not improving. Your doctor may suggest trying some strategies for addressing the problem without ignoring the health of your heart. Again, he or she may lower the dose or switch you to a different medicine.”
Stopping beta blockers suddenly can lead to something called the beta-blocker rebound phenomenon. This includes symptoms of an increased heart rate, high blood pressure, chest pain, and even heart failure symptoms. Speak with a doctor before stopping your medication, and they may taper you off the drug.
If a doctor decides to switch you to a different blood pressure medication, a variety of options are available.
Could my antidepressant be causing drowsiness?
Hergert says, “Generally speaking, antidepressants are known to cause sleep problems, including drowsiness. These medicines work by acting on certain neurotransmitters in the brain called serotonin and norepinephrine. These both elevate mood. But at the same time, the medicines can make you feel drowsy.
If your doctor prescribes an antidepressant, ask about the best time of day to take it. For instance, mirtazapine (Remeron) and trazodone (Desyrel) are often taken at bedtime. This is because they are known to cause drowsiness.
Other kinds of antidepressants, such as selective serotonin reuptake inhibitors, are not as likely to cause drowsiness. So you may be advised to take those during the daytime.”
Like beta-blockers, you shouldn’t suddenly stop taking your antidepressants. If you’re experiencing excess drowsiness, a healthcare professional is likely to slowly reduce your dosage to lower the chance of withdrawal symptoms.
Are there other things I can do if I feel drowsy during the day?
Hergert recommends practicing good sleep hygiene. You can also avoid drinking caffeine close to your bedtime. Caffeine has a half-life of up to 6 hours, which means half of it will still be in your system 6 hours after consumption. Knowing this can help you decide when to drink your coffee.
“That starts with a consistent sleep schedule, and you should avoid caffeinated drinks late in the day.
Also, if you take over-the-counter medications, try to avoid any that may contribute to drowsiness. And avoid alcohol while taking medication. It could make you even drowsier.”
Hergert also recommends eating a healthy diet and exercising regularly — but not too close to bedtime.
“A 30-minute walk is a good way to boost your energy. If you can’t get outside, try walking around your house 2 or 3 times a day for 10 or 15 minutes each time. That can really help.”
Summary
Drowsiness is a known side effect of many different medications, and antihistamines like Benadryl are among the most common. It’s different for everyone, but it’s most likely related to how the medications work on the brain.
If you’re experiencing unwanted side effects, there are steps you can take. You can speak with a doctor to change your medication, wait it out to see if the effect goes away with time, or take steps to manage sleepiness directly. These include exercising more and eating healthily.
Kawauchi H, et al. (2019). Antihistamines for allergic rhinitis treatment from the viewpoint of nonsedative properties. https://www.mdpi.com/1422-0067/20/1/213
