BENZTROPINE MES 0.5 MG TAB

Uses Dosage and Administration Cautions Drug Interactions

Uses

Benztropine mesylate is used for the adjunctive treatment of all forms of parkinsonian syndrome including the postencephalitic, idiopathic, and arteriosclerotic types. Benztropine is also used for the relief of parkinsonian signs and symptoms of antipsychotic agent-induced (e.g., phenothiazines) extrapyramidal reactions except tardive dyskinesia. Benztropine may be used alone or in conjunction with other antiparkinsonian drugs. Geriatric patients who do not tolerate cerebral-stimulating agents may respond to benztropine.

Dosage and Administration

Administration

Benztropine mesylate is administered orally or by IM injection. Parenteral administration should be reserved for patients who cannot take oral medication or for emergency situations, such as acute dystonic reactions, when rapid response is desired. Although benztropine may also be administered IV, the manufacturer states that there is no clinically important difference in onset between IM or IV injection; therefore, IV administration of the drug is rarely necessary.

Dosage

Parkinsonian Syndrome

Dosage of benztropine mesylate should be individualized according to the age and weight of the patient and the type of parkinsonian syndrome being treated. Geriatric patients or those with less than average body weight generally cannot tolerate high dosages of the drug.

For the adjunctive treatment of arteriosclerotic, idiopathic, or postencephalitic parkinsonian syndrome, the usual adult oral or parenteral dosage of benztropine mesylate is 1-2 mg daily (range: 0.5-6 mg daily). Benztropine therapy should be initiated at low dosages and gradually increased by 0.5-mg increments at 5- or 6-day intervals to a maximum dosage of 6 mg daily or until optimum symptomatic relief is obtained. For the arteriosclerotic and idiopathic types of parkinsonian syndrome, patients should be started on a single daily dose of 0.5-1 mg at bedtime. The dosage is then increased in increments of 0.5 mg every few days until the optimum tolerated dosage is reached. The increments may be added to the single daily dose or given as separate doses up to 4 times daily. Sometimes a single dose of 2 mg, usually given at bedtime, is sufficient to control symptoms for 24 hours. Younger patients with postencephalitic parkinsonian syndrome may tolerate larger initial doses and may require 2 mg 2 or 3 times daily for maintenance therapy. Older patients may be controlled with 1 or 2 mg daily.

Periodic dosage adjustment may be required in patients receiving benztropine with levodopa or a combination of levodopa and carbidopa to maintain optimum symptomatic relief. When benztropine is given to replace or supplement other antiparkinsonian drugs, the change should be gradual, with the dosage of the previous medication reduced as the dosage of benztropine is increased.

Drug-Induced Extrapyramidal Reactions

For the symptomatic relief of antipsychotic agent-induced extrapyramidal reactions (except tardive dyskinesia), the recommended oral or parenteral dosage of benztropine mesylate is 1-4 mg once or twice daily. Dosage must be individualized according to the patient's response and tolerance. For the symptomatic relief of extrapyramidal disorders that develop shortly after initiation of antipsychotic (e.g., phenothiazines) therapy, 1-2 mg 2 or 3 times daily usually provides relief within 1 or 2 days. Since acute extrapyramidal symptoms are generally transient, the need for benztropine should be reevaluated after 1-2 weeks of therapy.

For the relief of an acute dystonic reaction, 1-2 mg of benztropine mesylate may be given IV, followed by 1-2 mg orally twice daily to prevent recurrence.

Cautions

Adverse Effects

Adverse reactions to benztropine are mainly extensions of its anticholinergic and antihistaminic effects. Dryness of the mouth, blurred vision, mydriasis, nausea, nervousness, tachycardia, or skin rash may occur. In high dosage or in particularly susceptible patients, mental confusion and excitement, weakness and inability to move certain muscle groups, and, occasionally, urinary retention and/or difficulty in urination may result. Constipation, numbness of the extremities, listlessness, depression, vomiting, paralytic ileus, hyperthermia, fever, heat stroke, and visual hallucinations have also been reported. Adjustment of dosage will usually overcome most adverse effects of benztropine, but in the event of severe reactions, such as excitement or vomiting, the drug should be withdrawn and later resumed at a lower dosage.

Precautions and Contraindications

Benztropine should be used with caution or may be contraindicated in patients with conditions in which anticholinergic effects are undesirable. The usual precautions and contraindications associated with antimuscarinics should be observed with benztropine. For a complete discussion of the precautions and contraindications associated with antimuscarinics,.

Since benztropine has cumulative effects, continuous supervision of patients receiving the drug is advised, especially for those with a tendency toward tachycardia, or with prostatic hypertrophy. Patients with mental disorders receiving benztropine for control of drug-induced extrapyramidal effects should also be carefully observed, especially at the beginning of therapy or during dosage adjustment, since worsening of mental symptoms or toxic psychosis can occur.

Patients receiving benztropine concomitantly with phenothiazines or other drugs with anticholinergic effects should be warned to promptly report any adverse GI effects, since paralytic ileus, sometimes fatal, has occurred during concomitant therapy with these drugs.

Benztropine should not be used in patients with tardive dyskinesia, since the drug generally does not relieve signs and symptoms of this condition and may aggravate them. Benztropine is also contraindicated in patients with hypersensitivity to the drug or other components of the tablet or parenteral preparation.

Pediatric Precautions

Benztropine is contraindicated in children younger than 3 years of age and should be used with caution in older children because of the drug's adverse anticholinergic effects.

Pregnancy

Safe use of benztropine during pregnancy has not been established.

Drug Interactions

Concomitant administration of benztropine with other drugs having anticholinergic effects may increase the risk of adverse anticholinergic effects. Concomitant administration of an anticholinergic antiparkinsonian agent (e.g., benztropine) with phenothiazines and/or tricyclic antidepressants may cause paralytic ileus, hyperthermia, or heat intolerance, effects that occasionally have been fatal. Patients who are receiving benztropine concomitantly with phenothiazines, haloperidol, or other drugs with anticholinergic or antidopaminergic activity should notify their clinicians promptly if adverse GI effects, fever, or heat intolerance occurs.

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