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 (MAO_B) 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