Cogentin (Benztropine)

Last updated Feb. 14, 2022, by Teresa Carvalho, MS

✅ Fact-checked by Ana de Barros, PhD

Cogentin (benztropine) is a medicine developed by Merck Sharp & Dohme that is used as an add-on therapy to treat symptoms, such as stiffness or tremors, of Parkinson’s disease.

The treatment also is used for symptoms that may appear as a side effect of certain psychiatric medicines (antipsychotics).

The therapy was approved by the U.S. Food and Drugs Administration in oral tablets, although this formulation was discontinued, but not for reasons of safety or effectiveness. It is currently available as an injectable therapy manufactured by Akorn Pharmaceuticals. Several generic formulations also are available.

How Cogentin works

Cogentin is an anticholinergic that works by decreasing the effects of acetylcholine. Acetylcholine is a neurotransmitter — or chemical messenger — that is found at the junction between nerve cells and muscle cells.

Anticholinergic agents have different actions and clinical uses in various conditions.

They decrease secretions from the nose and bronchi, as well as the production of saliva, tears, sweat, and gastric acid. They also may be used to decrease secretions in allergic and inflammatory diseases. These agents help relax smooth muscle in the digestive system, bladder, and lungs and therefore have uses in gastrointestinal, urological, or respiratory conditions.

Some anticholinergics help prevent motion sickness and nausea, and vomiting during surgeries. They also help reverse neuromuscular blockers used during anesthesia and may be used to treat slow heart rhythm (bradycardia).

It is thought that Cogentin also increases the availability of dopamine, a naturally occurring chemical messenger in the brain that is very important in the initiation and smooth control of voluntary muscle movement. Of note, low levels of dopamine in the brain are associated with Parkinson’s.

Cogentin in clinical trials for Parkinson’s

A randomized, placebo-controlled, double-blind, cross-over trial assessed the efficacy of Cogentin in people with mild to moderate, idiopathic (of unknown cause) Parkinson’s disease. The study enrolled 29 patients who were treated with Sinemet (carbidopa-levodopa), a therapy used to treat motor symptoms associated with Parkinson’s. Patients were randomly assigned to receive either Sinemet plus Cogentin or Sinemet plus a placebo.

The results showed that those treated with Sinemet plus Cogentin had small but statistically significant improvements in rigidity, finger tapping speed, and activities of daily living. At the end of the trial, 16 patients chose to keep taking Cogentin as an add-on therapy to Sinemet.

Other information

Cogentin injection is available in a strength of 1 mg/ml. In patients with idiopathic parkinsonism, the treatment is usually prescribed to be taken at bedtime with a single daily dose of 0.5 to 1 mg. The starting dose may be increased slowly with time, after observing the patient’s response to treatment. It should not be stopped suddenly as Parkinson’s symptoms may return.

In emergency cases, 1 to 2 mL of the injection may provide a quick relief of the symptoms.

Common side effects include depression, disorientation, dizziness, drowsiness, hallucinations, and headache. Heat stroke, impaired memory, nervousness, numbness of fingers, and trembling of hands may also be observed.

Other symptoms may occur, such as blurred vision, dilated pupils, and increased sensitivity to light.

Digestive side effects, such as constipation, dry mouth, loss of appetite, nausea, and upset stomach, also may also be experienced.

Other adverse reactions include fast heartbeat, urinary retention (a condition in which the bladder doesn’t empty), and muscle weakness.

People with mental disorders should be cautiously observed, mainly at the beginning of treatment.

Hazardous tasks, such as operating machinery or driving should be avoided as Cogentin may impair mental and/or physical abilities.

Cogentin should not be used alongside tricyclic antidepressants, and antipsychotic medicines such as phenothiazines or haloperidol. People with an eye condition called glaucoma also should avoid Cogentin.

Additional information can be found on Cogentin’s label.


Parkinson’s News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.


Your Parkinson’s Community

Woman laying down illustration

Visit the Parkinson’s News Today forums to connect with others in the Parkinson’s community.

View Forums