Download Roach: Introductory Clinical Pharmacology

Introductory Clinical
Pharmacology
Chapter 32
Antiparkinsonism Drugs
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
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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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
Anticholinergics: Interactions
Interactant drug
Amantadine
Digoxin
Effect of interaction
Increased
anticholinergic effects
Increased digoxin serum
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
COMT Inhibitors: Interactions
Interactant drug
MAOI antidepressants
Effect of interaction
I
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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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
Dopamine Receptor Agonists:
Interactions
Interactant drug
Cimetidine, ranitidine
Effect of interaction
Increased agonist
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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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.
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
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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
Copyright © 2008 Lippincott Williams & Wilkins.
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
Copyright © 2008 Lippincott Williams & Wilkins.