ADVERSE REACTIONS SECTION.

ADVERSE REACTIONS. 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 hydrochloride 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 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 tolerance through the initial administration of small dose and gradual increase in dose until an effective level is reached. If severe reaction should occur, administration of the drug should be discontinued for few days and then resumed at 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.To report SUSPECTED ADVERSE REACTIONS, contact Novitium Pharma LLC at 1-516-305-1658 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.

DOSAGE & ADMINISTRATION SECTION.

DOSAGE ADMINISTRATION. Dosage should be individualized. The initial dose should be low and then increased gradually, especially in patients over 60 years of age. Whether trihexyphenidyl hydrochloride may best be given before or after meals should be determined by the way the patient reacts. Postencephalitic patients, who are usually more prone to excessive salivation, may prefer to take it after meals and may, in addition, require small amounts of atropine which, under such circumstances, is sometimes an effective adjuvant. If trihexyphenidyl hydrochloride tends to dry the mouth excessively, it may be better to take it before meals, unless it causes nausea. If taken after meals, the thirst sometimes induced can be allayed by mint candies, chewing gum or water.Trihexyphenidyl Hydrochloride in Idiopathic ParkinsonismAs initial therapy for parkinsonism, mg may be administered the first day. The dose may then be increased by mg increments at intervals of three to five days, until total of to 10 mg is given daily. The total daily dose will depend upon what is found to be the optimal level. Many patients derive maximum benefit from this daily total of to 10 mg, but some patients, chiefly those in the postencephalitic group, may require total daily dose of 12 to 15 mg.Trihexyphenidyl Hydrochloride in Drug-Induced ParkinsonismThe size and frequency of dose of trihexyphenidyl hydrochloride needed to control extrapyramidal reactions to commonly employed tranquilizers, notably the phenothiazines, thioxanthenes, and butyrophenones, must be determined empirically. The total daily dosage usually ranges between and 15 mg, although, in some cases, these reactions have been satisfactorily controlled on as little as mg daily. It may be advisable to commence therapy with single mg dose. If the extrapyramidal manifestations are not controlled in few hours, the subsequent doses may be progressively increased until satisfactory control is achieved. Satisfactory control may sometimes be more rapidly achieved by temporarily reducing the dosage of the tranquilizer on instituting trihexyphenidyl hydrochloride therapy and then adjusting dosage of both drugs until the desired ataractic effect is retained without onset of extrapyramidal reactions.It is sometimes possible to maintain the patient on reduced trihexyphenidyl hydrochloride dosage after the reactions have remained under control for several days. Instances have been reported in which these reactions have remained in remission for long periods after trihexyphenidyl hydrochloride therapy was discontinued.Concomitant Use of Trihexyphenidyl Hydrochloride with LevodopaWhen trihexyphenidyl hydrochloride is used concomitantly with levodopa, the usual dose of each may need to be reduced. Careful adjustment is necessary, depending on side effects and degree of symptom control. Trihexyphenidyl hydrochloride dosage of to mg daily, in divided doses, is usually adequate.Concomitant Use of Trihexyphenidyl Hydrochloride with Other Parasympathetic InhibitorsTrihexyphenidyl Hydrochloride may be substituted, in whole or in part, for other parasympathetic inhibitors. The usual technique is partial substitution initially, with progressive reduction in the other medication as the dose of trihexyphenidyl hydrochloride is increased.Trihexyphenidyl Hydrochloride Tablets The total daily intake of trihexyphenidyl hydrochloride tablets is tolerated best if divided into doses and taken at mealtimes. High doses (> 10 mg daily) may be divided into parts, with doses administered at meal times and the fourth at bedtime.

GENERAL PRECAUTIONS SECTION.

GENERAL PRECAUTIONS. Although trihexyphenidyl hydrochloride is not contraindicated for patients with cardiac, liver, or kidney disorders, or with hypertension, such patients should be maintained under close observation.Since the use of trihexyphenidyl hydrochloride may, in some cases, continue indefinitely and since it has atropine- like properties, patients should be subjected to constant and careful long-term observation to avoid allergic and other untoward reactions. In as much as trihexyphenidyl hydrochloride possesses some parasympatholytic activity, it should be used with caution in patients with glaucoma, obstructive disease of the gastrointestinal or genitourinary tracts, and in elderly males with possible prostatic hypertrophy.Geriatric patients, particularly over the age of 60, frequently develop increased sensitivity to the actions of drugs of this type, and hence, require strict dosage regulation. Incipient glaucoma may be precipitated by parasympatholytic drugs such as trihexyphenidyl hydrochloride.Tardive dyskinesia may appear in some patients on long term therapy with antipsychotic drugs or may occur after therapy when these drugs have been discontinued. Antiparkinson agents do not alleviate the symptoms of tardive dyskinesia and in some instances may aggravate them. However, parkinsonism and tardive dyskinesia often coexist in patients receiving chronic neuroleptic treatment, and anticholinergic therapy with trihexyphenidyl hydrochloride may relieve some of these parkinsonism symptoms.

PRECAUTIONS SECTION.

PRECAUTIONS. GENERAL PRECAUTIONS. Although trihexyphenidyl hydrochloride is not contraindicated for patients with cardiac, liver, or kidney disorders, or with hypertension, such patients should be maintained under close observation.Since the use of trihexyphenidyl hydrochloride may, in some cases, continue indefinitely and since it has atropine- like properties, patients should be subjected to constant and careful long-term observation to avoid allergic and other untoward reactions. In as much as trihexyphenidyl hydrochloride possesses some parasympatholytic activity, it should be used with caution in patients with glaucoma, obstructive disease of the gastrointestinal or genitourinary tracts, and in elderly males with possible prostatic hypertrophy.Geriatric patients, particularly over the age of 60, frequently develop increased sensitivity to the actions of drugs of this type, and hence, require strict dosage regulation. Incipient glaucoma may be precipitated by parasympatholytic drugs such as trihexyphenidyl hydrochloride.Tardive dyskinesia may appear in some patients on long term therapy with antipsychotic drugs or may occur after therapy when these drugs have been discontinued. Antiparkinson agents do not alleviate the symptoms of tardive dyskinesia and in some instances may aggravate them. However, parkinsonism and tardive dyskinesia often coexist in patients receiving chronic neuroleptic treatment, and anticholinergic therapy with trihexyphenidyl hydrochloride may relieve some of these parkinsonism symptoms.