8 Cogentin (Benztropine) Side Effects You Should Know About
Key takeaways:
Cogentin (benztropine) is an anticholinergic medication. It treats movement-related symptoms due to Parkinson’s disease. It also treats movement-related problems that occur as a side effect of other medications. It’s only available in the generic form, benztropine.
The most common Cogentin side effects are nausea, dry mouth, and constipation. It can also cause blurry vision.
Although rare, Cogentin may also cause more serious side effects. Examples include urinary retention, serious digestive problems, and heatstroke. Fast heart rate and mental health-related side effects are also possible.
Table of contents
Cogentin (benztropine) is an anticholinergic medication. It's FDA-approved to treat symptoms of all forms of Parkinson’s disease. It’s also used to reduce movement-related side effects caused by some antipsychotics.
Many people take Cogentin long term. So if you’re prescribed this medication, it’s helpful to know what side effects to expect. Most Cogentin side effects are mild, but severe side effects can happen in rare instances.
The brand-name Cogentin is no longer available. Still, we’ll refer to benztropine as Cogentin throughout this article since this name is well-known.
Cogentin side effects at a glance
Cogentin side effects are often mild and improve over time. But some may prompt you to call your healthcare professional if you experience them. And in rare cases, emergency treatment may be needed.
Mild Cogentin side effects include:
Slightly increased heart rate
Blurry vision
Nausea
Dry mouth
Constipation
Rare but serious Cogentin side effects include:
Trouble peeing
Very fast heart rate
Intestinal blockage
Vision problems
Inability to drive or complete tasks that require focus
Hyperthermia and heatstroke (due to reduced sweating)
Confusion, hallucinations, and other symptoms of psychosis
Read on to learn more about eight Cogentin side effects and how to manage or prevent them.
Anticholinergic medication overview: Cogentin is an anticholinergic medication, but it’s not the only one out there. Combining several anticholinergics can make side effects worse, so it’s a good idea to know if you take more than one.
Treatments for Parkinson’s disease: Cogentin may be used alongside other medications to treat Parkinson’s disease. Learn about different treatment options here.
Living with Parkinson’s disease: One man discusses his journey to continue hiking after he received his Parkinson’s disease diagnosis.
1. Fast heart rate
Some people may experience a fast heart rate (tachycardia) when taking Cogentin. This is because Cogentin works by blocking the action of a chemical called acetylcholine. One effect of acetylcholine is slowing your heart rate. So when Cogentin blocks acetylcholine, your heart rate may speed up.
Before you start taking Cogentin, let your prescriber know if you have heart problems. If so, they’ll need to monitor your heart rate closely during treatment. They may also want to monitor you more closely if you take multiple anticholinergic medications. So make sure you provide them with an up-to-date medication list.
If you notice symptoms of tachycardia, such as a pounding or racing heartbeat, let your prescriber know right away.
2. Constipation
Cogentin may cause constipation. This side effect can happen because Cogentin blocks acetylcholine, which slows the movement of food through your digestive system.
Luckily, you can take a few steps to prevent or relieve constipation caused by Cogentin:
Stay hydrated. Drinking enough water makes it easier for stool to pass through your gut.
Exercise regularly. Being physically active relieves or prevents constipation.
Enjoy a fiber-rich diet. Increasing your intake of high-fiber foods — such as beans, whole grains, and vegetables — can bulk up and soften your stool, making it easier to pass.
If you follow these tips and still experience constipation, over-the-counter (OTC) laxatives, such as senna (Senokot) or polyethylene glycol (Miralax), may be helpful. But be sure to talk with your pharmacist or prescriber before taking any OTC medication. They can make sure it doesn’t interact with Cogentin.
If your constipation doesn’t improve despite trying these tips or medications for about a week, talk to your prescriber as soon as possible. In rare cases, constipation may become severe and lead to a bowel obstruction. So if you’re having severe abdominal pain, rectal bleeding, or an inability to pass stool (feeling like it’s stuck), seek emergency care.
3. Nausea
Nausea is another possible Cogentin side effect. Vomiting may also occur.
If you experience nausea, ask your prescriber if you can take Cogentin at night, which may help you avoid some daytime nausea. You can also follow tips to ensure you’re not making your nausea worse. These include eating smaller but more frequent meals throughout the day and avoiding foods that can worsen nausea, such as spicy or greasy foods.
If your nausea continues or worsens while taking Cogentin, let your prescriber know. They may recommend decreasing your Cogentin dose. Or they may recommend OTC or prescription nausea medications if a dose reduction isn’t possible.
4. Dry mouth
Dry mouth can also happen with Cogentin. Typically, acetylcholine stimulates glands in your mouth to make saliva. When acetylcholine activity is blocked by Cogentin, saliva production may decrease, resulting in dry mouth.
You may be able to manage dry mouth at home by sipping on cool fluids or sucking on ice chips throughout the day. Chewing sugar-free gum with xylitol in it has also been shown to increase saliva production. You may also try OTC saliva substitutes, such as Biotene, to see if they help.
If your dry mouth continues, talk to your prescriber. They may recommend decreasing your Cogentin dose or suggest trying a prescription medication to treat dry mouth.
5. Blurry vision
Blurry vision is another possible side effect of anticholinergic medications, including Cogentin. This happens because blocking acetylcholine causes your pupils to dilate, which can lead to eye issues including blurry vision.
Blurry vision is more likely to occur with high doses of Cogentin. So only take Cogentin exactly as your prescriber recommends. If you’re experiencing blurry vision, avoid driving until your vision improves.
In rare cases, Cogentin may cause or worsen certain types of glaucoma. So if you have glaucoma, let your prescriber know. Depending on the type you have, they may recommend avoiding Cogentin.
6. Trouble peeing
Trouble peeing (urinary retention) can occur with anticholinergics such as Cogentin. This is because acetylcholine helps your bladder muscles contract to release pee. Since Cogentin blocks acetylcholine, it can lead to urinary retention.
Symptoms of urinary retention may include an inability to completely empty your bladder when you urinate and a frequent feeling that you need to pee, but being unable to do so.
Let your prescriber know if you have trouble peeing while you’re taking Cogentin. And let them know if you have a condition that increases your risk of urinary retention, such as benign prostatic hyperplasia (enlarged prostate).
7. Hyperthermia and heatstroke
Cogentin can reduce your body’s ability to sweat. In rare cases, this may lead to hyperthermia or heatstroke.
Hyperthermia happens when your body is unable to cool itself down, and your body temperature rises quickly. Heatstroke is a type of hyperthermia that occurs when your body is unable to sweat. This is a rare, but serious Cogentin side effect that can cause long-term organ damage and even death if not treated immediately.
Certain conditions can increase your risk of having hyperthermia or heatstroke while taking Cogentin, such as working outside or exercising in hot weather.
Symptoms of heatstroke can include very high body temperature (103℉ or higher), hot and dry skin, and confusion. If you’re taking Cogentin, stay hydrated, especially if it’s hot out. Avoid being outside during the hottest parts of the day, and avoid direct sunlight.
Heatstroke is a medical emergency. Seek medical care immediately if you think you or someone else is having heatstroke.
8. Confusion
In rare cases, Cogentin can cause confusion and visual hallucinations (seeing things that aren’t really there). These symptoms may be due to drug-induced psychosis. While the risk of this side effect is uncommon, it is possible while taking Cogentin.
This side effect may be more likely to occur when you first start taking Cogentin or after your dose is increased. Let your prescriber know if you feel confused or have hallucinations while taking Cogentin. They’ll likely recommend that you stop taking the medication if Cogentin is the cause.
Frequently asked questions
Many Cogentin side effects are mild and don’t last long, since they improve as your body gets used to the medication. What’s more, they can often be managed with lifestyle adjustments or a dosage decrease, as discussed above.
But some rare side effects — such as bowel obstruction, severe vision problems, or heatstroke — are more severe. If you experience them, your prescriber may want you to stop taking Cogentin.
Cogentin isn’t known to cause weight gain. However, some of its side effects, such as dry mouth or nausea, may lead to weight loss. If you have unexplained weight loss while taking Cogentin, talk to your prescriber.
Cogentin isn’t known to cause withdrawal symptoms after you stop taking it. Withdrawal symptoms are side effects that may happen after stopping a medication suddenly. Symptoms may include nausea or vomiting, tremor, or diarrhea. Anxiety and restlessness can also occur.
But while stopping Cogentin doesn’t cause withdrawal symptoms, it may cause your Parkinson’s disease symptoms or movement-related problems to return. So talk with your prescriber if you would like to stop taking Cogentin. They can recommend a different medication to treat your condition.
The bottom line
Cogentin (benztropine) is an anticholinergic medication. It treats movement-related symptoms due to Parkinson’s disease or certain medications. Cogentin is only available as the generic form benztropine.
Most Cogentin side effects occur because it blocks a chemical in your body called acetylcholine. This can lead to a fast heartbeat, constipation, and dry mouth. It can also cause nausea, blurry vision, and trouble peeing. More seriously, Cogentin can cause an intestinal blockage, heatstroke, and confusion.
Let your prescriber and pharmacist know what medications you take before starting Cogentin. They can check to see if you’re taking other medications that may increase your risk of side effects.
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References
Alhejoury, H. A., et al. (2021). Artificial saliva for therapeutic management of xerostomia: A narrative review. Journal of Pharmacy & BioAllied Sciences.
Migirov, A., et al. (2023). Physiology, anticholinergic reaction. StatPearls.
National Institute of Diabetes and Digestive and Kidney Diseases. (2019). Symptoms & causes of urinary retention.
National Institutes of Health. (2012). Hyperthermia: Too hot for your health.
RemedyRepack Inc. (2024). Benztropine mesylate- benztropine mesylate tablet [package insert].
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