Friday, April 6, 2012

ANTI-PARKINSON'S DISEASE DRUGS


CARBIDOPA-LEVODOPA

·         Carbidopa inhibits peripheral levodopa enzyme (decarboxylase) so that the levodopa can cross the blood-brain barrier efficiently.
·         Levodopa resolves dopamine deficiency by being converted to dopamine after crossing blood-brain barrier.
·         Ratio: 1 part carbidopa to 10 parts levodopa
·         Improves all the symptoms of Parkinsonism, especially bradykinesia and rigidity.
·         Contraindication: Patients with severe cardiac, renal or psychiatric health problems
·         Brand names: Sinemet®, Atamet®

Side effects:

·         Nausea and vomiting
·         Dyskinesia
·         Orthostatic hypotension
·         Cardiac arrhythmias
·         Psychoses (e.g paranoia, hallucination) and abnormal behavior (increased libido)
·         Dark urine and perspiration

MAO-B INHIBITORS
(also see antidepressant drugs)

·         Inhibits the enzyme (MAOB) that breaks down dopamine in the basal ganglia; enables dopamine to remain active for longer periods of time
·         It is used during the early disease to slow progression. It allows less levodopa to be used to achieve effects similar to larger doses of levodopa hence prolonging the onset of end-of-dose deterioration.

Example: selegiline/deprenyl (Eldepryl®, Zelapar®, Emsam® transdermal)

Side effects:

·         Dizziness
·         Stomach pain & heart burn
·         Dry mouth
·         Diarrhea
·         Nausea & vomiting
·         Dysphagia

AMANTADINE

·         An antiviral medication that has a stimulating or enhancing effect in the release of remaining dopamine in the basal ganglia which in turn could delay the necessity of levodopa therapy.
·         Common brand names: Symadine®, Symmetrel®

Side effects:

·         Orthostatic hypotension
·         Urinary retention
·         Confusion
·         Constipation
·         Purple mottling
·         Insomnia

DOPAMINE AGONIST

·         Directly stimulate dopamine receptors in basal ganglia
·         Enhances the effect of Sinemet therapy. It is used when levodopa responsiveness is diminishing

Example:
Generic names
Brand names
bromcriptine
Parlodel®
pergolide mesylate
Permaz®
pramipexole
Mirapex®
ropinirole
Requip®

Side effects:

·         Nausea
·         Palpitation
·         Hypotension
·         Edema
·         Chest pain
·         Hallucinations and confusion

ANTICHOLINERGICS

·         Inhibits excessive acetylcholine influence caused by dopamine deficiency
·         N.b single daily doses are best given at bed time.
·         Indication: Useful in control of tremor. Minimal effect on rigidity and bradykinesia
·         Contraindication: patient with glaucoma, myasthenia gravis, GI obstruction, achalasia, prostatic hypertrophy

Example:
Generic names
Brand names
benztropine
Cogentin®
trihexyphenidyl
Artane®
biperiden
Akineton®
ethoproprazine
Parsidol®
orphenadrine
Disipal®, Norlfex®, Banflex®
procyclidine
Kemadrin®

Side effects:

·         Dry mouth
·         Blurred vision
·         Urinary retention
·         Tachycardia
·         Constipation
·         Restlessness and confusion

CATHECOL-O-METHYLTRANSFERASE INHIBITORS (COMT)

·         Adjunct to Sinemet therapy to treat patients with the signs and symptoms of end-of-dose deterioration"wearing-off".
·         Usually used in combination with Sinemet®
·         Contraindications: patients taking MAO-1 inhibitors

Example: entacapone (Comtan®), tolcapone (Tasmar®)

Side effects: intensify the adverse effects of levodopa (e.g restlessness, loss of balance control, dysarthria, dysphagia)


BETA-BLOCKERS (see antihypertensive drugs)

·         Used to reduce the severity of tremors
·         Example: propanolol

Nursing Consideration:

ü  Check for fluctuations in symptoms related to dosing (end-of-dose deterioration, on-off phenomenon, dyskinesia). These are common with disease progression and long-term use of levodopa (e.g 2-3 years of use).
ü  Check for signs of orthostaic hypotension: weakness, dizziness or syncope.
ü  Avoid high protein diet. Spread protein intake thoughout the day.  High caloric diet is also recommended.
ü  Advise patient not to abruptly discontinue Sinemet therapy. Rebound parkinsonism may occur.
ü  Inform the patient about the effects of medication on secretions (e.g urine or perspiration may be dark)
ü  Advise the patient to avoid foods rich in Vitamin B6 (pyridoxine) and such as cereals and beans. It increases the potency of dopa decarboxylase
ü  Be vigilant for signs of hypertensive crisis especially for patients taking levodopa combined with MAO inhibitor antidepressant

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