Trihexyphenidyl dosing

Trihexyphenidyl (Artane) and benztropine (Cogentin) are prescription drugs used in the treatment both of Parkinson s disease and the extrapyramidal side effects produced by neuroleptic medication. They are occasionally abused for their mind-altering properties, which occur at toxic doses (Perry et al. 1978). Abusers often try to obtain these drugs by false representation of extrapyramidal symptoms, which are claimed to result from the use of phenothi-azines or other neuroleptics (Rubinstein 1978). 

AChs are an effective treatment (see Table 71-4). Benztropine has a half-life that allows once- to twice-daily dosing. Dose increases above 6 mg/day must be slow because of nonlinear pharmacokinetics. Trihexyphenidyl, diphenhydramine, and biperiden usually require three-times-daily dosing. Diphenhydramine produces more sedation, but all of the AChs have been abused for euphoriant effects. 

Digoxin (cardiac glycoside) and trihexyphenidyl (antimuscarinic drug) must be used with caution in elderly patients. Low doses are recommended in elderly patients to avoid toxicity. Lactulose may be safely administered to elderly patients with constipation. 

Reserve prolonged administration of doses exceeding 24 mg/day for hospitalized patients or patients under continued observation for early detection and management of adverse reactions. An antiparkinsonian agent, such as trihexyphenidyl hydrochloride or benztropine mesylate, is valuable in controlling drug-induced extrapyramidal symptoms. 

Parkinsonism - Initially, administer 1 to 2 mg the first day increase by 2 mg increments at intervals of 3 to 5 days, until a total of 6 to 10 mg is given daily. Many patients derive maximum benefit from a total daily dose of 6 to 10 mg however, postencephalitic patients may require a total daily dose of 12 to 15 mg. Trihexyphenidyl is tolerated best if divided into 3 doses and taken at mealtimes. High doses may be divided into 4 parts, administered at mealtimes and at bedtime. 

Concomitant use with levodopa Trihexyphenidyl 3 to 6 mg/day in divided doses is usually adequate. 

Trihexyphenidyl and biperiden have strong central and peripheral anticholinergic activity and both idiopathic as well as drug-induced Parkinsonism can be an indication for their use. Especially the tremor of Parkinsonism is favorably influenced. Large doses of trihexyphenidyl are said to have a mood modifying effect. The existence of a parenteral dosage forms of biperiden extends the applications of this agent. Both have a duration of action of 6-12 hours. 

Pleurothotonus (Pisa syndrome) is a special form of tardive dystonia that involves tonic flexion of the trunk to one side accompanied by slight backward rotation, in the absence of other dystonic symptoms. However, it can also occur immediately after the administration of neuroleptic drugs (SED-13,123). Nine of twenty patients (mean age 40 years) who developed Pisa syndrome while taking neuroleptic drugs (mean duration 12 years) improved within 3 weeks of treatment with trihexyphenidyl 12 mg/day (330). Reduction or withdrawal of the daily dose of the neuroleptic drugs was beneficial to the remaining patients. 

A 52-year-old woman developed Meige s syndrome 2 days after the appearance of akathisia. She had taken neuroleptic drugs for years, but her current medication had been changed to bromperidol 18 mg/day and trihexyphenidyl (benzhexol) 6 mg/day 2 days later she developed akathisia. Oral perphenazine 12 mg and trihexyphenidyl 6 mg dose-dependently reduced the frequency of blepharospasm the dosages of bromperidol and trihexyphenidyl were gradually reduced to 8 mg/ day and 3 mg/day respectively over 3 months, by which time her symptoms had completely disappeared. 

Although it has been thought that high doses of trihexyphenidyl might impair learning in children, a careful study of this question suggested that there is in practice little interference (657). 

ANTIMUSCARINICS ANALGESICS - PARACETAMOL Atropine, benzatropine, orphenadrine, procydidine and trihexyphenidyl may slow the onset of action of intermittent-dose paracetamol Anticholinergic effects delay gastric emptying and absorption Warn patients that the action of paracetamol may be delayed. This will not be the case when paracetamol is taken regularly... 

Of the drugs in this class used largely in parkinsonism, the tertiary amines related to diphenhydramine have some antihistaminic activity, as one would expect some of these drugs are also related to atropine. The derivatives of trihexyphenidyl (benzhexol) are also pharmacologically closely similar for example, they have some excitatory effects if given in sufficient doses. 

Trihexyphenidyl (benzhexol) is an anticholinergic drug. It is given in oral doses rising from 2 to 20 mg/day, and even higher doses are used in dystonic patients. A wide range of anticholinergic adverse reactions can occur, but trihexyphenidyl is apparently particularly likely to cause excitement. 

Corticosteroids (prednisone) in higher doses Anticholinergics (benztropine, trihexyphenidyl) Thyroid hormones (levothyroxine)... 

Answer C. Muscarinic receptor antagonists such as benztropine, trihexyphenidyl, and diphenhydramine are used to manage the reversible extrapyramidal dysfunction (e.g., pseu-do-Parkinsonism) that results from treatment with drugs that block DA receptors in the striatum. Drugs that activate DA receptors, although theoretically possible, require doses that are toxic and exacerbate psychoses. Because the actions of DA in the striatum lead to... 

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