Antiparkinsonism drug

Dopaminergic drug are drug that affect the dopamine content of the brain. These drag include levodopa (Larodopa), carbidopa(Ladosyn), amantadine (Symmetrel), 

The symptoms of parkinsonism are caused by a depletion of dopamine in the CNS. Dopamine, when given orally, does not cross the blood-brain barrier and therefore is ineffective The body s blood-brain barrier is a mesh-work of tightly packed cells in die walls of the brain s capillaries that screen out certain substances. This unique meshwork of cells in the CNS prohibits large and potentially harmful molecules from crossing into die brain. This ability to screen out certain substances lias important implications for drug dierapy because some drugs are able to pass through die blood-brain barrier more easily dian odiers. 

Levodopa is a chemical formulation found in plants and animals that is converted into dopamine by nerve cells in the brain. Levodopa does cross die blood-brain barrier, and a small amount is dien converted to dopamine. This allows the drug to have a pharmacologic effect in patients witii Parkinson s disease (Pig. 29-1). Combining levodopa witii another drug (carbidopa) causes more levodopa to reach die brain. When more levodopa is available, the dosage of levodopa may be reduced. Carbidopa has no effect when given alone. Sinemet is a combination of carbidopa and levodopa and is available in several combinations (eg, Sinemet 10/100 has 10 mg of carbidopa and 100 mg of levodopa Sinemet CR is a time-released version of die combined drugs). 

The mechanism of action of amantadine (Symmetrel) and selegiline (Eldepryl) in die treatment of parkinsonism is not fully understood. 

The dopaminergic drugs are used to treat die signs and symptoms of parkinsonism. As witii some otiier types of drugp, it may be necessary to change from one antiparkinsonism drug to anotiier or to increase or decrease die dosage until maximum response is obtained. 

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Discuss the uses, general drug action, adverse drug reactions, contraindications, precautions, and interactions of the antiparkinsonism drugs. 

Discuss important preadministration and ongoing assessment activities the nurse should perform on the patient taking antiparkinsonism drugs. 

Amantadine is less effective than levodopa in the treatment of Fhrkinson s disease but more effective than die anticholinergics. Amantadine may be given alone or in combination witii an antiparkinsonism drug witii anticholinergic activity. Amantadine is also used as an antiviral drug (see Chap. 14). 

Chap. 31), and during lactation. Levodopa is used cautiously in patients with cardiovascular disease, bronchial asthma, emphysema, peptic ulcer disease, renal or hepatic disease and psychosis. Levodopa and combination antiparkinsonism drugs (eg, carbidopa/levodopa) are classified as Pregnancy Category C and are used with caution during pregnancy and lactation. 

A newer classification of antiparkinson drugs is the catechol-O-methyltransferase (COMT) inhibitors. Examples of the COMT inhibitors are entacapone (Comtan) and tolcapone (Tasmar). 

I younger adult receiving the antiparkinsonism drugs especially when taking the dopamine receptor agonists The nurse should assess the older adult for sgns of visual, auditory, or tactile hallucinations The incidence of halludnationsappears to increase with age. 

Do not abruptly discontinue use of the antiparkinsonism drugs Neuroleptic malignant-like syndrome may occur when the antiparkinsonism drugs are discontinued or the dosage of levodopa is reduced abruptly. The nurse carefully observes the patient and reports the following symptoms muscular rigidity, elevated body temperature, and mental changes... 

Extrapyramidal effects usually diminish with a reduction in the dosage of the antipsychotic drug. The primary health care provider may also prescribe an antiparkinsonism drug, such as benztropine (see Chap. 29) to reduce the incidence of Parkinson-like symptoms. 

A patient taking chlorpromazine (Thorazine) for schizophrenia is also prescribed die antiparkinson drug benztropine What is the best explanation for adding an antiparkinson drug to die drug regimen ... 

Conventional kinetic resolution of diastereomer mixtures by retroaldolization for preparation of enantiopure arylserines and for a synthetic intermediate of an antiparkinsonism drug (b). 

Prescription and nonprescription anticholinergics Antiparkinson drugs Trihexyphenidyl (Artane)... 

Ricaurte GA, McCann UD, Szabo Z, et al Toxicodynamics and long-term toxicity of the recreational drug 3,4-methylenedioxy-methamphetamine (MDMA, Ecstasy ). Toxicol Lett 112-113 143-146, 2000 Robinson TN, Killen JD, Taylor CB, et al Perspectives on adolescent substance use a defined population study. JAMA 258 2072-2076, 1987 Rubinstein JS Abuse of antiparkinson drugs feigning of extrapyramidal symptoms to obtain trihexyphenidyl. JAMA 239 2365, 1978 Rumack BH (ed) LSD, in Poisindex, Vol 54. Denver, CO, Micromedex, 1987 Rusyniak DE, Banks ML, Mills EM, et al Dantrolene use in 3,4-methylenedioxymethamphetamine ( ecstasy )-medicated hyperthermia (letter). Anesthesiology 10 263, 2004... 

Thirty-five to eighty-seven percent of the patients studied received antiparkinson drugs. Compared to other countries, Japan and Singapore used the most of these antidotes for drug-induced extrapyramidal symptoms. This is most likely related to the frequent use of high-dosage antipsychotic drugs and poly-antipsychotics (see Table 12.3). 

Manyam BV, Dhanasekaran M, HareTA, Effect of antiparkinson drug HP-200 Mucunapruriens) on the central monoaminergic neurotransmitters, Phytotherapy Res... 

Combination therapy Other antiparkinson drugs can be given concurrently dosage adjustment may be necessary. 

Parkinson s disease 100 mg twice/day when used alone. Onset of action is usually within 48 h. Initial dose is 100 mg/day for patients with serious associated medical illnesses or those receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once/day, increase to 100 mg twice/day, if necessary. Patients whose responses are not optimal at 200 mg/day may occasionally benefit from an increase up to 400 mg/day in divided doses supervise closely. Patients initially benefiting from amantadine often experience decreased efficacy after a few months. Benefit may be regained by increasing to 300 mg/day, or by temporary discontinuation for several weeks. Other antiparkinson drugs may be necessary. 

Opioids, antiepileptics, levodopa, antiparkinsonism drugs, psychotropic drugs, anticholinergics Corticosteroids, diuretics... 

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