Trihexyphenidyl Side Effects

Please note - some side effects for Trihexyphenidyl may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA at http://www.fda.gov/medwatch/ or 1-800-FDA-1088 (1-800-332-1088).

Side Effects of Trihexyphenidyl - for the Consumer

Trihexyphenidyl

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Trihexyphenidyl:

Blurred vision; constipation; dizziness; drowsiness; dry mouth; headache; increased sensitivity of the eyes to light; lightheadedness; loss of appetite; nausea; nervousness; trembling of the hands; vomiting; weakness.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); agitation; chest pain; confusion; delusions; difficult swallowing; difficult urination; facial pain or swelling; fast or pounding heartbeat; fever or chills; hallucinations; mood or mental changes; severe constipation; swollen throat glands; uncontrolled movements.

Trihexyphenidyl Elixir

All medicines may cause side effects, but many people have no, or minor, side effects. Check with your doctor if any of these most COMMON side effects persist or become bothersome when using Trihexyphenidyl Elixir:

Blurred vision; constipation; dizziness; drowsiness; dry mouth; headache; increased sensitivity of the eyes to light; lightheadedness; loss of appetite; nausea; nervousness; trembling of the hands; vomiting; weakness.

Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); agitation; chest pain; confusion; delusions; difficult swallowing; difficult urination; facial pain or swelling; fast or pounding heartbeat; fever or chills; hallucinations; mood or mental changes; severe constipation; swollen throat glands; uncontrolled movements.

Trihexyphenidyl Side Effects - for the Professional

Trihexyphenidyl

Minor side effects, such as dryness of the mouth, blurring of vision, dizziness, mild nausea or nervousness, will be experienced by 30 to 50 percent of all patients. These sensations, however, are much less troublesome with Trihexyphenidyl HCl than with belladonna alkaloids and are usually less disturbing than unalleviated parkinsonism. Such reactions tend to become less pronounced, and even to disappear, as treatment continues. Even before these reactions have remitted spontaneously, they may often be controlled by careful adjustment of the dosage form, amount of drug, or interval between doses.

Isolated instances of suppurative parotitis secondary to excessive dryness of the mouth, skin rashes, dilatation of the colon, paralytic ileus, and certain psychiatric manifestations such as delusions and hallucinations, plus one doubtful case of paranoia all of which may occur with any of the atropine-like drugs, have been rarely reported with Trihexyphenidyl hydrochloride.

Patients with arteriosclerosis or with a history of idiosyncrasy to other drugs may exhibit reactions of mental confusion, agitation, disturbed behavior, or nausea and vomiting. Such patients should be allowed to develop a tolerance through the initial administration of a small dose and gradual increase in dose until an effective level is reached. If a severe reaction should occur, administration of the drug should be discontinued for a few days and then resumed at a lower dosage. Psychiatric disturbances can result from indiscriminate use (leading to overdosage) to sustain continued euphoria.

Potential side effects associated with the use of any atropine-like drugs include constipation, drowsiness, urinary hesitancy or retention, tachycardia, dilation of the pupil, increased intraocular tension, weakness, vomiting, and headache.

The occurrence of angle-closure glaucoma due to long-term treatment with Trihexyphenidyl hydrochloride has been reported.

Trihexyphenidyl Elixir

Minor side effects, such as dryness of the mouth, blurring of vision, dizziness, mild nausea or nervousness, will be experienced by 30 to 50 percent of all patients. These sensations, however, are much less troublesome with Trihexyphenidyl than with belladonna alkaloids and are usually less disturbing than unalleviated parkinsonism. Such reactions tend to become less pronounced, and even to disappear, as treatment continues. Even before these reactions have remitted spontaneously, they may often be controlled by careful adjustment of dosage form, amount of drug, or interval between doses.

Isolated instances of suppurative parotitis secondary to excessive dryness of the mouth, skin rashes, dilatation of the colon, paralytic ileus, and certain psychiatric manifestations such as delusions and hallucinations, plus one doubtful case of paranoia all of which may occur with any of the atropine-like drugs, have been reported rarely with Trihexyphenidyl.

Patients with arteriosclerosis or with a history of idiosyncrasy to other drugs may exhibit reactions of mental confusion, agitation, disturbed behavior, or nausea and vomiting. Such patients should be allowed to develop a tolerance through the initial administration of a small dose and gradual increase in dose until an effective level is reached. If a severe reaction should occur, administration of the drug should be discontinued for a few days and then resumed at a lower dosage. Psychiatric disturbances can result from indiscriminate use (leading to overdosage) to sustain continued euphoria.

Potential side effects associated with the use of any atropine-like drugs include constipation, drowsiness, urinary hesitancy or retention, tachycardia, dilation of the pupil, increased intraocular tension, weakness, vomiting, and headache.

The occurrence of angle-closure glaucoma due to long-term treatment with Trihexyphenidyl has been reported.

Trihexyphenidyl Tablets

Minor side effects, such as dryness of the mouth, blurring of vision, dizziness, mild nausea or nervousness, will be experienced by 30 to 50 percent of all patients. These sensations, however, are much less troublesome with Trihexyphenidyl HCl than with belladonna alkaloids and are usually less disturbing than unalleviated parkinsonism. Such reactions tend to become less pronounced, and even to disappear, as treatment continues. Even before these reactions have remitted spontaneously, they may often be controlled by careful adjustment of dosage form, amount of drug, or interval between doses.

Isolated instances of suppurative parotitis secondary to excessive dryness at the mouth, skin rashes, dilatation of the colon, paralytic ileus, and certain psychiatric manifestations such as delusions and hallucinations, plus one doubtful case of paranoia all of which may occur with any of the atropine-like drugs, have been reported rarely with Trihexyphenidyl hydrochloride.

Patients with arteriosclerosis or with a history of idiosyncrasy to other drugs may exhibit reactions of mental confusion, agitation, disturbed behavior, or nausea and vomiting. Such patients should be allowed to develop a tolerance through the initial administration of a small dose and gradual increase in dose until an effective level is reached. If a severe reaction should occur, administration of the drug should be discontinued for a few days and then resumed at a lower dosage. Psychiatric disturbances can result from indiscriminate use (leading to overdosage) to sustain continued euphoria.

Potential side effects associated with the use of any atropine-like drugs include constipation, drowsiness, urinary hesitancy or retention, tachycardia, dilation of the pupil, increased intraocular tension, weakness, vomiting, and headache.

The occurrence of angle-closure glaucoma due to long-term treatment with Trihexyphenidyl has been reported.

Side Effects by Body System

General

Most adverse effects of trihexyphenidyl are extensions of its pharmacologic activity and are anticholinergic in nature. Between 30% and 50% of all patients experience minor side effects (dry mouth, nausea, blurred vision, dizziness, nervousness). Elderly patients and those with underlying organic brain disease tend to be the most susceptible, especially to the central effects.

Gastrointestinal

Gastrointestinal side effects have included dry mouth, difficulty swallowing, anorexia, constipation, nausea, and vomiting. A reduction in dosage will sometimes help alleviate these problems. Paralytic ileus may develop, particularly in patients on concomitant phenothiazine or tricyclic antidepressant therapy, and may occasionally be fatal. Upon withdrawal of medication, nausea and vomiting may occur due to a cholinergic rebound.

Nervous system

Bucco-linguo-masticatory dyskinesias and chorea have been reported mostly in elderly patients being treated for Parkinson's disease with various anticholinergic agents, including trihexyphenidyl.

Nervous system side effects have included depression, anxiety, listlessness, drowsiness, numbness of fingers and dyskinesia. Chorea has been reported at higher dosages (>=15 mg/day). Trihexyphenidyl may also aggravate symptoms of tardive dyskinesia or elicit previously suppressed symptoms. Sleepwalking has been attributed to drugs or combination of drugs with anticholinergic activity.

Cognitive deficits, such as impairment of recent and short-term memory and inability to concentrate, may occur with clinical doses of anticholinergic agents and may be dose-related.

Psychiatric

Psychiatric side effects have included toxic psychosis which manifested as confusion, disorientation, agitation, excitation, memory impairment, delusions and hallucinations (usually visual, but may be auditory or tactile or all three), at toxic and therapeutic dosages (2% to 4%, up to 19% in elderly patients). Psychiatric deterioration and psychotic flare-ups have also been reported following withdrawal of therapy. Symptoms include delusions, hallucinations, aggression or violent behavior, and suicidal tendencies. In high dosages, trihexyphenidyl may sometimes produce euphorigenic effects. For this reason, it can be a drug of abuse.

Toxic psychosis, when present, tends to occur quickly, generally within several days to a week of initiating trihexyphenidyl therapy or within hours after an acute overdose. However, occasionally the onset may be delayed by months. Symptoms generally resolve spontaneously within a few days after the discontinuation of medication.

Ocular

Ocular side effects have included blurred vision, mydriasis, and cycloplegia. Trihexyphenidyl may also cause angle-closure glaucoma, which has rarely led to blindness.

Cardiovascular

Cardiovascular side effects have included tachycardia, although an isolated case of bradycardia has also been described. Orthostatic hypotension has been reported during withdrawal syndromes following discontinuation of long-term trihexyphenidyl therapy.

Genitourinary

Genitourinary side effects have included urinary retention and dysuria.

Metabolic

Metabolic side effects have included alterations in thermal homeostasis as a result of trihexyphenidyl's inhibition of the body's sweating mechanism. Heat stroke, hyperthermia, and fever have occurred with anticholinergic agents, most commonly in patients on concomitant neuroleptic or tricyclic antidepressant therapy.

Other

Anticholinergic poisoning syndrome may persist for more than a week's duration following trihexyphenidyl overdose. Most patients with anticholinergic intoxication require only supportive therapy of vital functions and/or discontinuation of medications. However, severely agitated, delirious, or comatose patients may be treated with physostigmine salicylate, an acetylcholinesterase inhibitor with both central and peripheral effects.

Anticholinergic intoxication may present with central and peripheral symptoms including those listed above, in addition to warm and dry skin, EKG abnormalities, insomnia, twitching or jerking movements, pantomime activity with nonexistent objects, hyperactivity, hyperreflexia, respiratory arrest, delirium, convulsions, shock and coma.

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