Benztropine (Injection)

Benztropine is an injectable medicine used to treat certain symptoms related to Parkinson's disease and similar symptoms related to the use of certain antipsychotic drugs.


Benztropine is the generic, injectable solution of the brand-name medication Cogentin. It is commonly used to treat the symptoms of parkinsonism, such as muscle spasms, stiffness, tremors, drooling and poor muscle control.

These symptoms also manifest as side effects (extrapyramidal disorders) in patients with serious mental and emotional disorders who are being treated with phenothiazine antipsychotic medications, such as prochlorperazine.

Benztropine works by blocking or reducing the effects of chemicals in the body that cause the symptoms of parkinsonism and drug-induced movement disorders. The results are improved muscle control, reduced stiffness and more normal movements of the body. While providing relief, the medicine may result in serious side effects, which patients must seriously consider.

Treatment with this prescription-only drug is by injection of Benztropine solution into a vein (intravenous) or injection into a muscle (intramuscular). They are both administered by a doctor or healthcare professional. In addition to treating symptoms of Parkinson's disease and similar symptoms related to the use of certain drugs, it may also be used for purposes not discussed here.

Conditions treated

  • Parkinsonism

Type of medicine

  • Anticholinergic

Side effects

The side effects of Benztropine may differ depending on whether it is injected into a vein or muscle. Call 911 or your doctor immediately if you experience symptoms of an allergic reaction, for example, swelling of the throat, tongue, lips or face and difficulty breathing or hives.

More common side effects

  • drowsiness
  • fast heartbeat
  • feeling nervous or excited
  • constipation
  • nausea and upset stomach
  • dry mouth (mild)
  • blurred vision or increased sensitivity to light
  • trouble urinating

These side effects are generally mild and may go away within a few days or a couple of weeks. If they are more severe or do not go away, talk to your doctor or seek urgent medical care.

Serious side effects

Call your doctor immediately if you experience any of the following symptoms of a serious side effect:

  • an allergic reaction, for example skin rash
  • fast, irregular, or pounding heartbeat
  • fever or raised body temperature
  • confusion, disorientation or memory loss
  • hallucinations or delusions
  • eye pain
  • difficult or painful urination
  • mood or mental changes such as depression, nervousness, unusual laziness or sleepiness
  • numb fingers
  • seeing things that are not actually there
  • worsening symptoms of existing mental illness
  • com/health/heat-stroke/">heat stroke
  • urine retention (it becomes impossible to empty your bladder)

Other serious side effects with incidence unknown may also occur. If you notice any other effects that seem severe or bothersome, tell your doctor or call 911. You can report any side effects you experience to the FDA by calling 1-800-FDA-1088.

Incidence unknown

Toxic psychosis, also known as substance-induced psychosis, has been reported in patients with both Parkinson's disease and medicine-induced movement disorders. Its symptoms are hallucinations (when patients see or hear or feel things that are not really there) or delusions (fixed false beliefs).

These reactions are more easily recognized in patients with Parkinson's disease than in psychiatric patients. The exact incidence of the occurrence of toxic psychosis is not known, but this side effect should not be excluded.

The frequency of the following side effects is not determined, though they can occur:

  • fever
  • headache
  • cramps or pain in the stomach or abdomen
  • hot, dry skin
  • bloated stomach
  • violent or aggressive behaviors
  • muscle weakness
  • feeling confused (eg, about where you are)
  • nervousness
  • difficulty with bowel movements
  • vomiting
  • forgetfulness
  • burning sensation while urinating

Some side effects may go away during treatment as the body adjusts to the medicine. These are generally mild and do not require medical attention.


A nurse or other trained health professional usually administers the medicine at a hospital or clinic. Carefully follow all directions given to you by them during therapy.

Dosage for children and adults may vary. Your doctor will determine your dose based on your age, symptoms and other medicines you may be taking during treatment.

For adults with Parkinson's disease

The dose will be given as an injection into the vein or muscle. For adults, this is usually 1 to 2 mg of Benztropine (Cogentin) per day, with a range of 0.5 to 6 mg per day. Dosages for children over three years of age are determined by a doctor on a case by case basis.

Some patients do better with divided doses, such as older patients. You may be prescribed a low dose at the beginning of therapy. Your doctor may then increase the dose based on your body's response to the medication.

Medicine-induced parkinsonism

When treating extrapyramidal disorders in psychiatric patients, a dosage of 1 to 4 mg once or twice a day is recommended. Dosage varies based on the needs of the patient.

If you miss a dose, call your doctor right away to find out what you should do.


If you suspect you overdosed on the medication, call 911, your doctor or the poison helpline at 1-800-222-1222.

Patients who overdose may experience dizziness, lightheadedness, numbness or tingling in the face, arms or legs, eye pain, blurred vision, wheezing and nosebleeds. Other symptoms of an overdose are as follows:

  • vision problems
  • decreased vision
  • blindness
  • cold, clammy, skin
  • loss of consciousness
  • seizures
  • shakiness or unsteady walk
  • muscle weakness
  • trembling, unsteadiness, or muscle control or coordination problems
  • sweating
  • nervousness, restlessness or unusual excitement
  • change in consciousness
  • nausea or vomiting
  • tearing
  • difficulty breathing
  • no breathing
  • delusion (holding fixed false beliefs that cannot be changed by facts)

Incidence not known

  • enlarged pupils
  • loss of appetite
  • skin rash
  • weight loss

Some of the symptoms of overdose are similar to some of the side effects. Seek urgent medical attention, even if you think the symptoms are normal.


Prescription and non-prescription drugs can interact with Benztropine, causing unwanted side effects or preventing the drug from working as it should. Some interactions may occur that are expected and required, particularly with drugs prescribed in addition to Benztropine during therapy.

Have a thorough discussion with your doctor to understand reactions to all possible diseases, conditions, foods, medicines and other agents you are currently using, have used in the past or will be using during your treatment.

Potassium, Oxymorphone and Tiotropium could significantly interact with Benztropine and are not recommended for use during therapy. Your doctor may decide not to treat you with Benztropine, change some of the other medicines you take, change the dose or change how often you use any of the them.

Betel nut, Chlorpromazine and Haloperidol may cause an increased risk of certain side effects. If prescribed together with Benztropine, your doctor may change the dose or how often you use any of them.

Alcohol, medicines that cause drowsiness or impair alertness, and those that contain anticholinergic agents may interact and add to the effects of Benztropine. Speak with your doctor if you are using or plan to use them during your treatment.

The medicine may also interact with some health problems, including the following:

  • com/health/coma/">glaucoma;
  • heart or blood pressure issues;
  • mental illness;
  • nerve-muscle disorder;
  • prostate problems;
  • bowel or bladder obstruction;
  • urination problems; and
  • liver or kidney disease;


Use Benztropine only when prescribed by a doctor or pharmacist.

This medication is not approved for use in children under the age of three. If you are an older adult or a pregnant or breastfeeding woman, the medication may not be safe to use. However, a doctor may still prescribe it to be used cautiously and under close supervision.

Patients who are allergic to Benztropine should not use it. Let your doctor know of any allergies to foods, dyes, preservatives or animals and call your doctor or seek emergency care if you have a severe allergic reaction to the medicine.

Do not drive or use machinery if side effects, such as drowsiness, dizziness, sleepiness or confusion, occur. To be safe, ask a friend or loved one to drive you home after your injection.

Stay cool while using the medicine during hot weather, as the medicine may reduce sweating and prevent your body from cooling itself off.

Do not stop taking this medication abruptly without talking to your physician first.

Do not use if you have Tardive Dyskinesia (movement disorder).


Since Benztropine is administered by a doctor or healthcare professional, it will be stored at your doctor's clinic or the hospital. The injection is kept in a cool dry place where the temperature stays below 30°C. The ampoules are kept in their package to protect them from light. It is not recommended that they be stored in the freezer.


Benztropine is used to treat the symptoms of Parkinson's disease and treat and prevent medicine-induced movement disorders, similar to parkinsonism, in patients being treated with antipsychotic medicines.

While its effectiveness is established, there is a list of side effects with incidence unknown. The list is also non-exhaustive. This means those side effects can occur at any time, in any patient, and without warning.

Because the frequency with which some side effects occur is not known, patients may not readily know whether a symptom experienced is a side effect or not. The ability to spot all side effects with certainty allows the patient to seek urgent medical attention, reducing the risks to health and life.

Benztropine may also cause serious side effects, such as mental confusion, excitement, nervousness, or hallucinations. This places an additional responsibility on both patient and doctor to closely monitor side effects.

Where toxic psychosis occurs, the reactions are easily recognized in patients with Parkinson's disease. It is challenging for both patients and healthcare professionals to distinguish the symptoms in psychiatric patients, as the reactions are similar in nature to some of their 'normal' behaviors. As such, closer clinical monitoring may be required.

Coincidentally, the medicine's use is cautioned in older patients, when Parkinson's disease is more likely to affect elderly people. This could present a challenge for effective treatment.

While this medication is mostly safe for use, the potential for serious side effects and adverse interaction with other medicines make it one that should only be taken after all factors are considered, and after concluding that the benefits outweigh the risks involved.