Trihexyphenidyl Hydrochloride

Adults: Dosing needs to be individualized for each patient. The starting dose should be kept low and increased gradually, especially in patients over 60 years of age. Whether Trihexyphenidyl is best taken before or after meals should be decided based on how the patient responds. Postencephalitic patients, who tend to be more prone to excessive salivation, may prefer taking it after meals and may also need small amounts of atropine, which can sometimes be a useful additional treatment in such cases. If Trihexyphenidyl tends to dry the mouth excessively, it may be better to take it before meals, unless doing so causes nausea. If taken after meals, any thirst it induces can sometimes be relieved with mint candies, chewing gum or water. Abruptly stopping treatment for Parkinsonism may cause a sudden worsening of Parkinsonism symptoms, so abrupt withdrawal should be avoided. Abrupt withdrawal of treatment may also result in neuroleptic malignant syndrome (NMS). Idiopathic Parkinsonism: As initial therapy for parkinsonism, a dose of 1 mg of Trihexyphenidyl may be given on the first day. The dose may then be increased in 2 mg increments at intervals of three to five days, until a total of 6 to 10 mg is given daily. The total daily dose depends on what is found to be the optimal level for the patient. Many patients get the most benefit from a daily total of 6 to 10 mg, but some patients, particularly those in the postencephalitic group, may need a total daily dose of 12 to 15 mg. Drug Induced Parkinsonism: The size and frequency of the Trihexyphenidyl dose needed to control extrapyramidal reactions to commonly used tranquilizers, notably the phenothiazines, thioxanthenes and butyrophenones, must be worked out for each patient. The total daily dosage usually ranges between 5 and 15 mg, although in some cases these reactions have been satisfactorily controlled with as little as 1 mg daily. It may be advisable to begin therapy with a single 1 mg dose. If the extrapyramidal symptoms are not controlled within a few hours, later doses may be gradually increased until satisfactory control is achieved. Satisfactory control can sometimes be reached more quickly by temporarily lowering the dose of the tranquilizer when starting Trihexyphenidyl therapy, and then adjusting the doses of both drugs until the desired calming effect is maintained without the onset of extrapyramidal reactions. It is sometimes possible to keep the patient on a reduced Trihexyphenidyl dose once the reactions have been under control for several days. There have been reports of these reactions staying in remission for long periods after Trihexyphenidyl therapy was stopped. Concomitant use with Levodopa: When Trihexyphenidyl is used concomitantly with levodopa, the usual dose of each may need to be lowered. Careful adjustment is needed, depending on side effects and the degree of symptom control achieved. A Trihexyphenidyl dosage of 3 to 6 mg daily, given in divided doses, is usually enough. Concomitant use with other Parasympathetic Inhibitors: Trihexyphenidyl may be substituted, in whole or in part, for other parasympathetic inhibitors. The usual approach is partial substitution at first, with the other medication progressively reduced as the dose of Trihexyphenidyl is increased. The total daily intake of Trihexyphenidyl tablet is best tolerated when divided into 3 doses and taken at mealtimes. Higher doses (above 10 mg daily) may be divided into 4 parts, with 3 doses given at mealtimes and the fourth at bedtime. Use in children: Safety and effectiveness in pediatric patients have not been established.