Trihexyphenidyl Benzatropine

Antagonists of muscarinic acetylcholine receptors had widely been used since 1860 for the treatment of Parkinson s disease, prior to the discovery of l-DOPA. They block receptors that mediate the response to striatal cholinergic interneurons. The antiparkinsonian effects of drugs like benzatropine, trihexyphenidyl and biper-iden are moderate the resting tremor may sometimes respond in a favorable manner. The adverse effects, e.g., constipation, urinary retention, and mental confusion, may be troublesome, especially in the elderly. 

These include atropine, scopolamine (hyoscine), trihexyphenidyl (benzhexol) and benzatropine. They block central muscarinic receptors involved in various afferent pathways of the vomiting reflex (Fig. 1). They have been used to control motion sickness, emesis in Meniere s disease and postoperative vomiting. Currently, hyoscine is largely restricted to the treatment of motion sickness where it has a fast onset of action but a short duration (4-6 h). Administration of hyoscine by transdermal patch produces a prolonged, low-level release of the drug with minimal side effects. To control postoperative vomiting, it should be applied >8 h before emesis is anticipated. 

ANTIMUSCARINICS -atropine, benzatropine, cydopentolate, dicydover-ine, flavoxate, homa-tropine, hyoscine, orphenadrine, oxybutynin, procydidine, propantheline, tolterodine, trihexyphenidyl, tropicamide 7. ANTI-PARKINSON S DRUGS -... 

NITRATES 1. ANALGESICS-nefopam 2. ANTIARRHYTHMICS -disopyramide, propafenone 3. ANTIDEPRESSANTS-TCAs 4. ANTI EMETICS-cydizine 5. ANTIHISTAMINES -chlorphenamine, cyproheptadine, hydroxyzine 6. ANTIMUSCARINICS -atropine, benzatropine, cydopentolate, dicydover-ine, flavoxate, homat-ropine, hyoscine, orphenadrine, oxybutynin, procyclidine, propantheline, tolterodine, trihexyphenidyl, tropicamide. 7. ANTI-PARKINSON S DRUGS-dopaminergics 8. ANTI-PSYCHOTICS - pheno-thiazines, clozapine, pimozide 9. MUSCLE RELAXANTS-baclofen 1. t risk of antimuscarinic side-effects when isosorbide dinitrate is co-administered with these drugs 2. 1 efficacy of sublingual nitrate tablets... 

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... 

Antimuscarinics Benzatropine, Biperiden, Bornaprine, Dexetimide, Metixene, Orphenadrine, Procyelidine, Profenamine, Trihexyphenidyl, Tropatepine... 

In a double-blind study 3 patients given a phenothiazine and benzatropine for the parkinsonian adverse effects, developed an intermittent toxic confusional state (marked disturbance of short-term memory, impaired attention, disorientation, anxiety, visual and auditory hallucinations) with peripheral antimusearinies signs. Similar reactions occurred in 3 elderly patients given imipramine or desipramine, with trihexyphenidyl, and in another man given chlorpromazine, benzatropine and doxepin. ... 

Other studies confirm that trihexyphenidyl and orphenadiine reduce the plasma levels and effects of chlorpromazine. In contrast to these reports, another found that trihexyphenidyl increased chlorpromazine levels by 41% in 20 young schizophrenics, but no clinical change was seen. The levels dropped again over the first 4 weeks of treatment. Some of the beneficial actions of haloperidol on social avoidance behaviour ate lost during concurrent treatment with benzatropine, but cognitive integrative function is unaffected. 

---