The P-I-E-N-O Parkinsn's List Drug Database
benztropine mesylate / CogentinTM
ANTIPARKINSON:
Anticholinergic
Description: Benztropine is an oral and parenteral synthetic muscarinic-receptor antagonist that is structurally similar to atropine and diphenhydramine. It is used adjunctively with other antiparkinsonian agents to treat all types of parkinsonian syndromes including antipsychotic-induced extrapyramidal symptoms. Although benztropine is a tertiary amine, and as such crosses into the CNS, it produces less CNS stimulation than does trihexyphenidyl. Benztropine has cumulative effects, and therapeutic benefit can take up to 2-3 days. Benztropine has a longer duration of action and may require less frequent dosing than diphenhydramine. The drug may be helpful in geriatric patients who cannot tolerate cerebral-stimulating agents. Benztropine was approved for use in 1954.
Mechanism of Action: Benztropine has anticholinergic, antihistaminic, and local anesthetic effects. Its anticholinergic activity is about half that of atropine; its antihistaminic activity is roughly equivalent to that of pyrilamine. Benztropine competes with acetylcholine, and perhaps other cholinergic mediators, at muscarinic receptors in the CNS and, to a lesser extent, in smooth muscle. By blocking cholinergic receptors in the CNS, benztropine reduces the excessive cholinergic activity present in parkinsonism and related states. Also, it can block dopamine reuptake and storage in CNS cells, thus prolonging dopamine's effects. In general, anticholinergic agents can help control tremor but are less effective for treating bradykinesia or rigidity.
Pharmacokinetics: Benztropine is administered orally and parenterally. It is absorbed from the GI tract, crosses the blood-brain barrier, and may cross the placenta. After oral administration, a small part of the dose may pass through the GI tract unchanged into the feces. Benztropine's metabolism is unknown, but most of the drug is excreted renally, both as parent drug and as metabolites.
CONTRAINDICATIONS/PRECAUTIONS: Benztropine is contraindicated in patients with closed-angle glaucoma because the drug can induce cycloplegia and mydriasis, resulting in increased intraocular pressure. Benztropine also should be used cautiously in patients with open-angle glaucoma.
Benztropine is relatively contraindicated in benign prostatic hypertrophy because it can exacerbate urinary retention.
Benztropine must be used cautiously in patients with cardiac disease and preexisting tachycardia because it causes tachycardia secondary to cholinergic antagonism at the SA node.
Benztropine should not be used in patients with tardive dyskinesia because it does not treat this condition and can exacerbate it.
In addition, benztropine should be used with caution in elderly patients (age > 65 years); neonates (age < 1 month); and infants (age 1 month-1 year) because these populations are more sensitive to the anticholinergic side effects of this drug.
DRUG INTERACTIONS: Concomitant use of benztropine with other drugs possessing anticholinergic activity can lead to anticholinergic toxicity. These drugs include amantadine, haloperidol, direct anticholinergics, antihistamines, tricyclic antidepressants, and phenothiazines. Reactions have included paralytic ileus, hyperthermia, and heat intolerance. Although additive anticholinergic effects are possible, combination therapy is sometimes necessary to control other unwanted side effects of a neuroleptic.
In high doses, metoclopramide can cause extrapyramidal reactions, which benztropine can counteract. Benztropine, however, also can antagonize the therapeutic effects of metoclopramide on GI motility.
Ethanol and other CNS depressants, such as anxiolytics, sedatives, and hypnotics, can increase the sedative effects of benztropine.
The doses of benztropine and levodopa/carbidopa must be adjusted when the drugs are given simultaneously. Benztropine should be expected to increase the dopaminergic effects.
Antacids and antidiarrheals decrease the absorption of oral benztropine. Give benztropine at least 1 hour before these drugs.
ADVERSE REACTIONS: Benztropine's adverse reactions are an extension of it's pharmacologic activity. Benztropine has both anticholinergic and antihistamine activity. Anticholinergic effects are usually minor with the use of normal doses but can be serious in an acute overdose or in combination with other drugs that also possess anticholinergic effects.
CNS adverse reactions of benztropine include disorientation, restlessness, excitement, amnesia, giddiness, psychosis, paranoia, delirium, delusions, euphoria, hallucinations, headache, and depression. Anxiety is experienced by 30-50% of all patients. More serious effects include agitation or confusion.
Ophthalmic adverse reactions include blurred vision, mydriasis, and cycloplegia. A more serious effect is the exacerbation of narrow-angle glaucoma. These effects are due to the anticholinergic activity of benztropine.
GI adverse reactions of benztropine include xerostomia. Patients should take the drug after meals and should suck on hard candy, chew gum, or drink water to relieve dry mouth. Other GI effects include constipation, nausea/vomiting, and paralytic ileus.
The anticholinergic effect of benztropine can decrease the amount of sweating and heat release from the body. Hyperthermia, fever, and heat stroke have been reported with benztropine.
Urticaria is seen with relative frequency in patients taking benztropine.
Other serious adverse reactions reported with benztropine include urinary retention, paresthesias, and sinus tachycardia.
PATIENT INFORMATION:
What do benztropine tablets do?
Benztropine (CogentinTM ) is a medicine that prevents or controls movement-related side effects of antipsychotic medicines (medicines for treating mental disorders). It also treats symptoms of parkinsonism from unknown causes. Symptoms such as tremor, rigid muscles and difficulties in walking, talking, balancing and swallowing. Generic benztropine tablets are available.
What should my doctor, dentist, or pharmacist know before I take benztropine?
They need to know if you have any of these conditions:
How should I take this medicine?
Take benztropine tablets by mouth. Follow the directions on the prescription label. Swallow the tablets with a drink of water. Take with food, unless your doctor instructs you otherwise. If you have difficulty swallowing you can crush the tablets and mix with food. Take your doses at regular intervals. Do not take your medicine more often than directed. It may take several days to see the full effect of benztropine; do not stop taking except on your doctor's advice.
Special precautions for use in children:
This medicine is not for children under 3 years old, and should be used with caution in older children.
Elderly patients are more likely to get side effects and should be given smaller doses.
What if I miss a dose?
If you miss a dose, take it as soon as you can. If it is almost time for your next dose (less than 2 hours), take only that dose. Do not take double or extra doses.
What other medicines can interact with benztropine?
Tell your doctor or pharmacist: about all other medicines you are taking, including non-prescription medicines; if you are a frequent user of drinks with caffeine or alcohol; if you smoke; or if you use illegal drugs. These may affect the way your medicine works. Check before stopping or starting any of your medicines.
What side effects may I notice from taking benztropine?
Serious side effects with benztropine include:
Call your doctor as soon as you can if you get any of these side effects.
Minor side effects with benztropine include:
Let your doctor know about these side effects if they do not go away or if they annoy you.
What do I need to watch for while I take benztropine?
Visit your doctor for regular checks on your progress. Do not stop taking this medicine abruptly. Your doctor may want to gradually reduce the dose so that you do not get side effects or make your condition worse. Your doctor may want you to have an eye exam from time to time.
You may get dizzy or have blurred vision. Do not drive, use machinery, or do anything that needs mental alertness until you know how benztropine affects you. To reduce the risk of dizzy or fainting spells, do not sit or stand up quickly, especially if you are an older patient. Alcohol can make you more dizzy, and increase flushing and rapid heartbeats. Avoid alcoholic drinks.
Your mouth may get dry. Chewing sugarless gum or sucking hard candy, and drinking plenty of water will help.
Stay out of bright light and wear sunglasses if benztropine makes your eyes more sensitive to light.
You may sweat less than usual while you are taking benztropine. As a result your body temperature could rise to a dangerous level. Be careful not to get overheated during exercise or in hot weather; you could get heat stroke. Avoid taking hot baths, and using hot tubs and saunas.
Antacid or diarrhea medicine can stop benztropine working. If you want to take antacid or diarrhea medicine, leave an interval of at least 2 hours before or after you take benztropine.
Where can I keep my medicine?
Keep out of the reach of children in a container that small children cannot open. Store at room temperature between 15 and 30C (59 and 86F). Keep container tightly closed. Throw away any unused medicine after the expiration date.
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