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Common Medicines That Can Make You Drowsy

It has become a common sight these days to find people on all sorts of medications for a variety of health conditions. While you would commonly associate feeling drowsy when you take a sleeping pill, there are many other types of medications as well that can make you feel drowsy and tired. In fact, feeling drowsy is one of the most common side effects of many over-the-counter and prescription medicines.

But why does this happen? Well, certain medications can make you feel drowsy because they have an impact on the chemicals present in your brain known as neurotransmitters. The nerves in the body use neurotransmitters to pass messages to one another. Some of these neurotransmitters also control how sleepy or awake you feel.

Common Medicines That Can Make You Drowsy

Common Medicines That Can Make You Drowsy

Here are some of the most common medicines that make you feel drowsy:

  1. Allergy Medications

    Allergy medications, or antihistamines, are one of the most common medications that cause you to feel drowsy. In fact, some antihistamines are contained in many sleeping pills as well. Some of the common allergy medications include:

    • Brompheniramine (brand name: Bromfed, Dimetapp)
    • Diphenhydramine
    • Hydroxyzine (brand name: Vistaril, Atarax)
    • Meclizine (Antivert)
    • Doxylamine Succinate

    Histamines are a type of chemical compound that play several roles in the body. They are primarily known for their role in the body’s immune response. When the body is under attack, the white blood cells and tissue cells present in your immune system release histamines to find and attach to other cells that have a receptor for the histamines. Then the histamines induce an inflammatory response. This means that they dilate the blood vessels while increasing blood flow to the site of invasion or injury. They also allow the blood vessels to become more permeable, which allows white blood cells and certain proteins to go past and reach the damaged or infected tissue to start the repairing work.(1, 2, 3, 4, 5)

    However, there are certain side effects to this process of healing that histamines carry out. Allergies occur when the immune system mistakes some seemingly ordinary object, such as pet dander or pollen, for being dangerous. Histamines start their job, which gives rise to many side effects such as chest congestion, itchy eyes, red eyes, sneezing, wheezing, runny nose, etc.

    Antihistamines are used to relieve the symptoms, but they also prevent some functions of histamines, which is the role histamines play in regulating the sleep and awake cycle. This disruption of the sleep and wakefulness cycle of histamines in the brain is what makes a person feel drowsy.(6, 7, 8, 9)

  2. Antidepressants

    One type of antidepressant known as tricyclics is known to make you feel sleepy and tired. This is because some types of antidepressants work by acting on the brain chemicals known as neurotransmitters, as described above as well. They especially act on the neurotransmitters known as serotonin and norepinephrine. This causes these compounds to keep lingering on in the spaces between the nerve cells. Here, these neurotransmitters carry out their job of regulating a person’s mood.(10, 11, 12)

    However, at the same time, these antidepressants affect some other neurotransmitters as well, including acetylcholine and histamine, which may cause other unpleasant adverse reactions as well, including sedation, dry mouth, weight gain and blurry vision. It is the side effect of sedation that is responsible for making you feel drowsy after taking an antidepressant.(13, 14)

    If you find yourself feeling too sleepy and struggling to even keep your eyes open, you should let your doctor know so that your antidepressant can be changed. When you are feeling like this, though, never get behind the wheels of a car. You should call a cab or allow someone else to drive you until you find a solution for your drowsiness.(15, 16)

    Some of the antidepressants that are most likely to make you feel drowsy are as follows:

    • Amitriptyline (brand name: Elavil, Vanatrip)
    • Doxepin (brand name: Silenor, Sinequan)
    • Imipramine (brand name: Tofranil, Tofranil PM)
    • Trimipramine (brand name: Surmontil)
  3. Anxiety Medications

    There are many different types of medications used to treat anxiety disorders, including conventional anti-anxiety medicines like benzodiazepines, which are usually prescribed for short-term use. Other newer options include SSRI (Selective Serotonin Reuptake Inhibitors) antidepressants that are typically recommended for long-term use in anxiety disorders. These medications successfully provide relief from anxiety symptoms, but they also have their share of side effects, which include making you feel drowsy.(17, 18, 19)

    Benzodiazepines that are prescribed for anxiety and cause sleepiness include:

    • Alprazolam (brand name: Xanax)
    • Clonazepam (brand name: Klonopin)
    • Diazepam (brand name: Valium)
    • Lorazepam (brand name: Ativan)

    These anti-anxiety medications can make you feel drowsy and even weak for several hours to even a few days, depending on which medicine you are on. This happens because benzodiazepines typically work by slowing down the nervous system, which helps you relax not just mentally but also physically. This means that the higher the dose, the more sleepy, foggy, and uncoordinated you will feel.(20, 21, 22)

Other Medications That Make You Feel Drowsy

There are many other medications that can make you feel tired and drowsy. Some of these include:

  • Blood Pressure Medicines: Blood pressure medicines like beta-blockers work by slowing down your heart rate. This makes you feel tired and drowsy. Common beta-blockers that can make you feel drowsy include atenolol (brand name: Tenormin), metoprolol tartrate (brand name: Lopressor), (brand name: Toprol XL), propranolol hydrochloride (brand name: Inderal), etc.
  • Medications For The Gut: Medications that help control nausea or treat diarrhea can also make you feel drowsy and tired.
  • Opioid Pain Relievers: Opioid medications are typically used to control pain. They work by acting like endorphins, which are chemicals the body produces for controlling and managing pain. Some common opioid pain medications that can make you feel sleepy include oxycodone (brand name: OxyContin), hydrocodone and acetaminophen (brand name: Lortab, Vicodin), fentanyl (brand name: Duragesic, Fentora), oxycodone and aspirin (brand name: Percodan), etc.
  • Cancer Drugs: Certain types of cancer treatments can make you feel excessively sleepy and exhausted as they change the levels of protein and hormones in your body. Since these medications kill cancer cells, they also end up damaging or destroying many normal cells. This means that your body has to put in extra time and energy to fix these cells, making you feel tired and sleepy.
  • Epilepsy or Seizure Drugs: Commonly known as anticonvulsants, these drugs work on the cells in your brain or on the chemicals the brain cells use to send messages to the rest of the body. Benzodiazepines are also included in this class of drugs. Other seizure medications that commonly make you feel sleepy include carbamazepine (brand name: Tegretol/Tegretol XR), phenytoin (brand name: Dilantin), phenobarbital, valproic acid, etc.

Conclusion: What To Do If Your Medication Makes You Feel Drowsy?

If you find that your medicine makes you feel tired and sleepy, never stop taking it by yourself without consulting your doctor. You should let your doctor know if it is becoming impossible for you to function after taking that medication. Otherwise, there are many other ways by which you can fight against these side effects and also get a boost of energy. For example, taking deep breaths, exercising regularly, drinking some coffee or tea, etc.

In extreme cases, your doctor will help you by changing your dosage, medication or even changing the time of taking your medication. They may also prescribe another medication that enables you to feel alert and awake. However, never take any medicine to remain awake that has not been prescribed by your doctor.


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  3. Brown, D.D., Tomchick, R. and Axelrod, J., 1959. The distribution and properties of a histamine-methylating enzyme. Journal of Biological Chemistry, 234(11), pp.2948-2950.
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Pramod Kerkar, M.D., FFARCSI, DA
Pramod Kerkar, M.D., FFARCSI, DA
Written, Edited or Reviewed By: Pramod Kerkar, M.D., FFARCSI, DA Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:September 23, 2022

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