Parkinsonism antiparkinsonian drugs

Trihexyphenidyl, an antiparkinsonian drug, possesses central and peripheral anticholinergic actions, as well as a direct relaxant effect on smooth muscle. It reduces muscle rigidity and general stiffness, and has a relatively minor effect on tremors. It is used in Parkinsonism in the form of monotherapy as well as in combination with levodopa. The most common synonyms are parkopan, parkinsan, and cyclodol. 

Studies (42 14) showed that patients treated with antiparkinsonian drugs suffer from sleep attacks. These attacks were responsible for traffic accidents (45) modafinil can efficiently counterbalance this symptom in patients suffering from Parkinson s disease (46). 

The neuroleptic drugs that elicit parkinsonism are those that bind with higher affinity than dopamine to D2 receptors, while those that cause little or no parkinsonism (clozapine, melperone, quetiapine) bind with lower affinity (234). Antiparkinsonian drugs are more often required in patients taking typical neuroleptic drugs, but they can cause objective and subjective deficits (235,236). 

Ethopropazine Hydrochloride, U5P. Ethopropa/.ine hydrochloride. l()- 2-(diethylaminu)propyl phenuthiazinc monohydrochloride (Parsidol). introduced to therapy in 1954, has antimu.scarinic activity and is especially useful in the symptomatic treatment of parkinsonism. In this capacity, it has value in controlling rigidity, and it also has a favorable effect on tremor, sialorrhea, and oculogyric crises. It is used often in conjunction with other antiparkinsonian drugs for complementary activity. 

The client diagnosed with Parkinson s disease has been taking amantadine (Symmetrel), an antiparkinsonian drug. The home health nurse notes a new finding of mottled discoloration of the skin. Which action should the nurse take ... 

In contrast, a case-control study of patients with Parkinson s disease taking levodopa therapy did not find a statistically significant increase in the required dose of antiparkinsonian drug treatment in the 180 days after starting a benzodiazepine. ... 

A retrospective study of patients with Parkinson s disease taking selegiline 5 to 10 mg daily (and other antiparkinsonian drugs such as levo-dopa/carbidopa, bromocriptine, amantadine, pergolide, and... 

Nervous system Serotonin syndrome with rhabdomyolysis occurred in a patient with Parkinson s disease after he had taken venlafaxine 75 mg/day for depression for 2 weeks [23" ]. Previous reports of serotonin syndrome with venlafaxine have been related to overdose [24 ]. Parkinsonism or drug-drug interactions with the antiparkinsonian medications may have predisposed this patient to serotonin syndrome at such low doses of venlafaxine. 

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. 

A final pharmacological strategy for treatment of Parkinson s disease comes from enzyme inhibition. This was initally done with an MAO inhibitor, L-deprenyl (selegiline, Eldepryl), but more recent drugs have become available that are COMT inhibitors. L-Deprenyl is an inhibitor of MAOB, which is the form of MAO selective to dopamine. Thus, it may increase the amount of available dopamine for release. Second, it may protect dopamine neurons by reducing the oxidative stress concomitant with dopamine metabolism (Olanow 1997). Third, L-deprenyl is metabolized into amphetamine and methamphetamine, which may contribute to their antiparkinsonian effects. Unlike other treatments for Parkinson s disease, L-deprenyl seems to slow the progression of the disease. Tolcapone (Tasmar) is a COMT inhibitor, which prevents extracellular breakdown of dopamine. 

Addition of other antiparkinsonian medications Standard drugs for Parkinson disease may be used concomitantly while carbidopa, levodopa, and entacapone... 

The efficacy of anticholinergic drugs in parkinsonism is likely due to the ability to block muscarinic receptors in the striatum. In the absence of the inhibitory action of dopamine, the actions of the intrastriatal cholinergic interneurons are unopposed, yielding enhanced stimulation of muscarinic receptors. Blockade of these receptors reduces striatal activity. The muscarinic antagonists exert only modest antiparkinsonian actions and thus are most commonly used during the early stages of the disease or as an adjunct to levodopa therapy. 

The other newer selective MAOIs that specifically inhibit MAO-B are ineffective for the treatment of depression and are mainly used for Parkinson s disease, and so are covered elsewhere, see Antiparkinsonian and related drugs , (p.672). In low doses they inhibit MAO-B, leaving MAO-A largely uninhibited. However, selegiline loses some of its seleetivity at doses of more than 10 mg daily and will therefore be subjeet to the same interactions as the non-selective MAOIs. Rasagiline is another irreversible selective inhibitor of MAO-B used for Parkinson s disease. 

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