Generic Name

Trihexyphenidyl Hydrochloride

Precaution

Patient w/ arteriosclerosis, history of drug idiosyncrasy. CV disease, glaucoma, GI obstruction, prostatic hyperplasia and/or urinary stricture. Not intended for treatment of tardive dyskinesia. Avoid abrupt withdrawal. Hepatic and renal impairment. Elderly. Pregnancy and lactation. Patient Counselling May impair mental or physical abilities e.g. operating machinery or driving. Monitoring Parameters Perform gonioscopic examination prior to initiation of therapy. Monitor intraocular pressure at regular intervals during prolonged treatment.

Indication

Extrapyramidal symptoms, Parkinsonism (postencephalitic, arteriosclerotic & idiopathic)

Contra Indication

Patients with closed-angle glaucoma, chronic pulmonary disease, sick sinus syndrome, thyrotoxicosis, cardiac failure with tachycardia.

Dose

N/A

Side Effect

>10% Anticholinergic side effects (30-50%), Rash <1% Suppurative parotitis,Hallucination,Paralytic ileus

Pregnancy Category

Mode of Action

Trihexyphenidyl HCl is a tertiary amine antimuscarinic which exerts a direct inhibitory effect on the parasympathetic nervous system. It also exhibits a direct spasmolytic action on smooth muscle, weak mydriatic, antisialagogue and cardiovagal blocking effects.

Interaction

Increased antimuscarinic side effects w/ phenothiazines, clozapine, antihistamines, disopyramide, nefopam and amantadine. Synergistic effect when concomitantly used w/ TCAs. Concurrent admin w/ MAOIs may cause dry mouth, blurred vision, urinary hesitancy or retention and constipation. May antagonise effect of metoclopramide and domperidone on GI function. Reduced absorption of levodopa. May antagonise effect of parasympathomimetics.

Pregnancy Category Note

Pregnancy Category: C Lactation: no data; may inhibit lactation

Adult Dose

Oral Drug-induced extrapyramidal symptoms Adult: 5-15 mg/day PO divided q6-8hr Parkinson Disease Adult: Initially, 1 mg daily, gradually increased at intervals of 3-5 days by increments of 2 mg until 6-10 mg daily in 3-4 divided doses. Maintenance: 5-15 mg/day PO divided q6-8hr Parkinsonism Adult: 5-15 mg/day PO divided q6-8hr Elderly: May require lower doses.

Child Dose

Safety and efficacy not established

Renal Dose

N/A

Administration

Should be taken with food. Best taken w/ meals. Take before meals if dry mouth occurs, after meals if drooling/nausea occurs. Take at the same time each day.