Introductory Clinical Pharmacology Chapter 32 Antiparkinsonism Drugs

Introductory Clinical Pharmacology Chapter 32 Antiparkinsonism Drugs

Dopaminergic Drugs: Actions Symptoms of parkinsonism are caused by depletion of dopamine in CNS Amantadine: makes more of dopamine available at receptor site Selegiline: inhibits monoamine oxidase type B, again making more dopamine available Combining levodopa with another drug allows more levodopa to reach brain, providing better pharmacologic effect in patients with Parkinson s disease

Dopaminergic Drugs: Uses Dopaminergic drugs are used to treat: Parkinson s disease Parkinson-like symptoms as a result of injury, drug therapy, or encephalitis Restless leg syndrome Viral infections

Dopaminergic Drugs: Adverse Reactions, Contraindications, and Precautions Dry mouth, difficulty in swallowing, anorexia, nausea, and vomiting, abdominal pain, constipation, increased hand tremor, headache, dizziness Adverse reactions seen with levodopa: choreiform movements, dystonic movements Contraindications Dopaminergic drugs: Patients with known hypersensitivity to the drugs

Dopaminergic Drugs: Adverse Reaction Contraindications, and Precautions (cont d) Levodopa: Patients with narrow-angle glaucoma and those receiving MAOI antidepressants Precautions Levodopa is used cautiously in patients with cardiovascular or pulmonary diseases; peptic ulcer disease; renal or hepatic disease; and psychosis Dopamine agonist (selegiline) should not be used with opioids (meperidine) due to antimetabolite conversion

Dopaminergic Drugs: Interactions Interactant drug Tricyclic antidepressants Antacids Effect of interaction Increased risk of hyperten sion and dyskines ia Increased effect of l e v o d

Anticholinergics: Actions Drugs with cholinergic blocking activity block Ach in CNS, enhancing dopamine transmission Antihistimines such as diphenhydramine are used in elderly patients, as they produce fewer adverse effects

Anticholinergics: Uses and Adverse Reactions Uses Used as adjunctive therapy in all forms of parkinsonism and in control of druginduced extrapyramidal disorders Adverse Reactions Dry mouth; blurred vision; dizziness; mild nausea; nervousness; skin rash; urticaria; urinary retention; dysuria; tachycardia; muscle weakness; disorientation; confusion

Anticholinergics: Contraindications and Precautions Contraindicated in patients with: Hypersensitivity to anticholinergic drugs; glaucoma; pyloric or duodenal obstruction; peptic ulcers; prostatic hypertrophy; achalasia; myasthenia gravis; megacolon Used with caution in patients with: Tachycardia; cardiac arrhythmias; hypertension; hypotension; a tendency toward urinary retention; decreased liver or kidney function; obstructive disease of urinary system or gastrointestinal tract

Anticholinergics: Interactions Interactant drug Amantadine Digoxin Effect of interaction Increased anticholinergic effects Increased digoxin serum

COMT Inhibitors: Actions and Uses Actions Prolong the effect of levodopa by blocking an enzyme, catechol-o-methyltransferase, which eliminates dopamine With levodopa, increased plasma concentration and duration of action of the levodopa Uses COMT inhibitors are used as adjuncts to levodopa/carbidopa in treating Parkinson s disease

COMT Inhibitors: Adverse Reactions, Contraindications, and Precautions Dizziness, dyskinesias, hyperkinesias, nausea, anorexia, diarrhea, orthostatic hypotension, sleep disorders, excessive dreaming, somnolence, muscle cramps, liver failure Contraindicated in patients with hypersensitivity to drugs and during pregnancy and lactation Caution in patients with hypertension; hypotension; decreased hepatic or renal function

COMT Inhibitors: Interactions Interactant drug MAOI antidepressants Effect of interaction I

Dopamine Receptor Agonists: Actions and Uses Actions Act directly on postsynaptic dopamine receptors of nerve cells in brain, mimicking effects of dopamine in brain Uses Used for treatment of signs and symptoms of Parkinson s disease

Dopamine Receptor Agonists: Adverse Reactions, Contraindications, Precautions Nausea; dizziness; vomiting; somnolence; hallucinations; confusion; visual disturbances; postural hypotension; abnormal involuntary movements; headache Contraindications: Patients with known hypersensitivity to drugs Precautions: Used with caution in patients with dyskinesia; orthostatic hypotension; hepatic or renal impairment; patients with history of hallucinations or psychosis; cardiovascular disease; renal impairment

Dopamine Receptor Agonists: Interactions Interactant drug Cimetidine, ranitidine Effect of interaction Increased agonist

Nursing Process: Assessment Preadministration assessment Obtain health history from family member Perform physical assessment of patient to provide baseline for future evaluations of drug therapy Ongoing assessment Evaluate patient s response to drug therapy by observing patients for various neuromuscular signs and comparing these observations with data obtained during initial physical assessment

Nursing Process: Planning Expected outcomes for patient may include: Optimal response to drug therapy Support of patient needs related to management of adverse reactions Absence of injury Understanding of and compliance with prescribed therapeutic regimen

Nursing Process: Implementation Promoting an optimal response to therapy Carefully monitor drug therapy; provide psychological support; emphasize patient and family teaching Requires titration of doses based on patient activities Withhold next dose of drug and immediately notify primary health care provider if sudden behavioral changes are noted

Nursing Process: Implementation Monitoring and managing patient needs Imbalanced nutrition: Less than bodily requirements Help patient relieve dry mouth by offering frequent sips of water, ice chips, or hard candy Create calm environment; serve small frequent meals; serve foods patient prefers to help improve nutrition Monitor patient s weight daily

Nursing Process: Implementation Monitoring and managing patient needs (cont d) Constipation Observe patient with parkinsonism for outward changes that may indicate one or more adverse reactions Stress need for diet high in fiber and increasing fluids in diet

Nursing Process: Implementation Monitoring and managing patient needs (cont d) Risk for injury Carefully evaluate any sudden changes in patient s behavior or activity and reports them to primary health care provider Assist patient in getting out of bed or a chair, walking, and other self-care activities

Nursing Process: Implementation Monitoring and managing patient needs (cont d) Impaired physical mobility If symptoms occur, primary health care provider may order a drug holiday that includes complete withdrawal of levodopa for 5 to 14 days, followed by gradually restarting drug therapy at lower dose

Nursing Process: Implementation Educating the patient and family Evaluate patient s ability to understand therapeutic drug regimen; ability to perform self-care in the home environment; ability to comply with prescribed drug therapy Encourage family to create a home environment that is least likely to result in accidents or falls

Nursing Process: Evaluation Therapeutic effect is achieved and the symptoms of parkinsonism are controlled Adverse reactions are identified, reported, and managed successfully through appropriate nursing interventions No evidence of injury is seen Patient verbalizes an understanding of treatment modalities, adverse reactions, and importance of continued follow-up care Patient and family demonstrate an understanding of drug regimen