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Chapter 20 Drugs for Degenerative Diseases of the Nervous System

Terms in this set (39)

Therapeutic Class: Antiparkinson drug

Pharmacologic Class: Dopamine precursor; dopamine-enhancing drug combination

Actions and Uses
Stalevo restores the neurotransmitter dopamine in extrapyramidal areas of the brain, thus relieving some Parkinson's symptoms, especially tremor, bradykinesia, gait, and muscle rigidity. To increase its effect, levodopa is combined with two other drugs, carbidopa and entacapone, which prevent its enzymatic breakdown. Several months may be needed to achieve maximum therapeutic effects.

Administration Alerts
The patient may be unable to self-administer medication and may need assistance.
Administer exactly as ordered.
Abrupt withdrawal of the drug can result in Parkinson'slike symptoms or neuroleptic malignant syndrome (NMS).
Pregnancy category C.

Adverse Effects :
Side effects of Stalevo include uncontrolled and purposeless movements such as extending the fingers and shrugging the shoulders, involuntary movements, loss of appetite, nausea, and vomiting. Muscle twitching and spasmodic winking are early signs of toxicity. Orthostatic hypotension is common in some patients. The drug should be discontinued gradually, because abrupt withdrawal can produce acute Parkinson'slike symptoms.

Contraindications:
Stalevo is contraindicated in the treatment of narrow-angle glaucoma. This drug is contraindicated in patients with suspicious pigmented lesions or a history of melanoma. This medication should be avoided in cases of acute psychoses and severe psychoneurosis within 2 weeks of therapy with monoamine oxidase inhibitors (M A O I s).

Interactions
Drug-Drug: Stalevo interacts with many drugs. Haloperidol taken concurrently may antagonize the therapeutic effects of Stalevo. Methyldopa may increase toxicity. Antihypertensives may cause increased hypotensive effects. Anticonvulsants may decrease the therapeutic effects of Stalevo. Antacids containing magnesium, calcium, or sodium bicarbonate may increase Stalevo absorption, which could lead to toxicity. Pyridoxine reverses the antiparkinson effects of Stalevo.

Lab Tests: Abnormalities in laboratory tests may include elevations of liver function tests such as alkaline phosphatase, aspartate aminotransferase (A S T), alanine aminotransferase (A L T), lactic dehydrogenase, and bilirubin. Abnormalities in blood urea nitrogen and positive Coombs' test have also been reported.

Herbal/Food: Kava may worsen the symptoms of Parkinson's.

Treatment of Overdose: General supportive measures should be taken along with immediate gastric lavage. Intravenous (I V) fluids should be administered judiciously, and an adequate airway should be maintained.
Therapeutic Class: Antiparkinson drug

Pharmacologic Class: Centrally acting cholinergic receptor blocker
Actions and Uses Benztropine acts by blocking excess cholinergic stimulation of neurons in the corpus striatum. It is used for relief of Parkinson's-like symptoms and for the treatment of EPS brought on by antipsychotic pharmacotherapy. This medication suppresses tremors but is not effective at relieving tardive dyskinesia.

Administration Alerts
The patient may be unable to self-administer medication and may need assistance.
Benztropine may be taken in divided doses, two to four times a day, or the entire day's dose may be taken at bedtime.
If muscle weakness occurs, the dose should be reduced.
Pregnancy category C.

Adverse Effects
As expected from its autonomic action, benztropine can cause typical anticholinergic side effects such as dry mouth, constipation, and tachycardia. Adverse general effects include sedation, drowsiness, dizziness, restlessness, irritability, nervousness, and insomnia.

Contraindications:
Contraindications include narrowangle glaucoma, myasthenia gravis, blockage of the urinary tract, severe dry mouth, hiatal hernia, severe constipation, enlarged prostate, and liver disease.

Interactions
Drug-Drug: Benztropine interacts with many drugs. Common medications that should not be used in combination with benztropine are aripiprazole (Abilify), lorazepam (Ativan), docusate (Colace), divalproex sodium (Depakote), gabapentin, ziprasidone (Geodon), haloperidol (Haldol), clonazepam (Klonopin), lamotrigine (Lamictal), lisinopril, lithium, metformin, fluoxetine (Prozac), risperidone (Risperdal), quetiapine (Seroquel), levothyroxine (Synthroid), topiramate (Topamax), trazodone, bupropion (Wellbutrin), sertraline (Zoloft), and olanzapine (Zyprexa).

Over-the-counter (O T C) cold medicines should be avoided. Drugs that enhance dopamine release or activate dopamine receptors may produce additive effects. Haloperidol decreases the effectiveness of benzotropine. Benztropine should not be taken with alcohol because of combined sedative effects. Antihistamines, phenothiazines, tricyclic antidepressants, disopyramide, and quinidine may increase anticholinergic effects, and antidiarrheals may decrease absorption.

Lab Tests: Unknown.

Herbal/Food: Unknown.

Treatment of Overdose: Physostigmine 1 to 2 mg subcutaneously or I V, will reverse symptoms of anticholinergic intoxication. A second injection may be given after 2 hours, if required. Otherwise, treatment is symptomatic and supportive.
Therapeutic Class: Alzheimer's disease drug

Pharmacologic Class: Cholinesterase inhibitor

Actions and Uses
Donepezil is an AchE inhibitor that improves memory in cases of mild to moderate Alzheimer's dementia by enhancing the effects of acetylcholine in neurons in the cerebral cortex that have not been damaged. Patients should receive pharmacotherapy for at least 6 months prior to assessing maximum benefits of drug therapy. Improvement in memory may be observed as early as 1 to 4 weeks following medication. The therapeutic effects of donepezil are often short lived, and the degree of improvement is modest, at best. An advantage of donepezil over other drugs in its class is that its long half-life permits it to be given once daily.

Administration Alerts
Give medication prior to bedtime.
Medication is most effective when given on a regular schedule.
Pregnancy category C.

Adverse Effects
Common side effects of donepezil are vomiting and diarrhea. Less common effects are abnormal dreams, fainting, and darkened urine. C N S side effects include insomnia, syncope, depression, headache, and irritability. Musculoskeletal side effects include muscle cramps, arthritis, and bone fractures. Generalized side effects include headache, fatigue, chest pain, increased libido, hot flashes, urinary incontinence, dehydration, and blurred vision. Hepatotoxicity has not been observed. Patients with bradycardia, hypotension, asthma, hyperthyroidism, or active peptic ulcer disease should be monitored carefully.

Contraindications: Donepezil is contraindicated in patients with G I bleeding and jaundice.

Interactions
Drug-Drug: Donepezil will cause anticholinergics to be less effective. Donepezil interacts with several other drugs. For example, bethanechol causes a synergistic effect. Phenobarbital, phenytoin, dexamethasone, and rifampin may speed the elimination of donepezil. Quinidine or ketoconazole may inhibit the metabolism of donepezil. Because donepezil acts by increasing cholinergic activity, two cholinergic drugs should not be administered concurrently.

Lab Tests: Unknown.

Herbal/Food: Unknown.

Treatment of Overdose: Anticholinergics such as atropine may be used as an antidote for donepezil overdosage. I V atropine sulfate titrated to effect is recommended: an initial dose of 1 to 2 mg I V with subsequent doses based on clinical response.