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Parkinson’s disease treatment

Uses

To slow or stop clinical progression of Parkinson’s disease and to improve function and quality of life in pts with Parkinson’s disease, a progressive neurodegenerative disorder.

Action

Normal motor function is dependent on the synthesis and release of dopamine by neurons projecting from the substantia nigra to the corpus striatum. In Parkinson’s disease, disruption of this pathway results in diminished levels of the neurotransmitter dopamine. Medication is aimed at providing improved function using the lowest effective dose.

TYPES OF MEDICATIONS FOR PARKINSON’S DISEASE DOPAMINE PRECURSOR

Levodopa/carbidopa:

Levodopa: Dopamine precursor supplementation to enhance dopaminergic neurotransmission. A small amount of levodopa crosses the blood-brain barrier and is decarboxylated to dopamine, which is then available to stimulate dopaminergic receptors.

Carbidopa: Inhibits peripheral decarboxylation of levodopa, decreasing its conversion to dopamine in peripheral tissues, which results in an increased availability of levodopa for transport across the blood-brain barrier.

COMT INHIBITORS

Entacapone, tolcapone: Reversible inhibitor of catechol-O-methyltransferase (COMT). COMT is responsible for catalyzing levodopa. In the presence of a decarboxylase inhibitor (carbidopa), COMT becomes the major metabolizing enzyme for levodopa in the brain and periphery. By inhibiting COMT, higher plasma levels of levodopa are attained, resulting in more dopaminergic stimulation in the brain and lessening the symptoms of Parkinson’s disease.

DOPAMINE RECEPTOR AGONISTS

Bromocriptine: Stimulates postsynaptic dopamine type 2 receptors in the neostriatum of the CNS.

Pramipexole: Stimulates dopamine receptors in the striatum of the CNS.

Ropinirole: Stimulates postsynaptic dopamine D2 type receptors within the caudate putamen in the brain.

MONOAMINE OXIDASE B INHIBITORS

Rasagiline, Selegiline: Increase dopaminergic activity due to irreversible inhibition of monoamine oxidase type B (MAO B). MAO B is involved in the oxidative deamination of dopamine in the brain.

Medications for treatment of Parkinson’s disease

Name	Type	Availability	Dosage	Side Effects
Bromocriptine (p. 157) (Parlodel)	Dopamine agonist	T: 2.5 mg C: 5 mg	1.25 mg bid, increase by 2.5 mg/dose in 2–4 wk intervals (Maximum: 100 mg/day)	Nausea, drowsiness, lower extremity edema, postural hypotension, confusion, toxic psychosis (avoid use in pts with dementia)
Carbidopa/levodopa (p. 191) (Parcopa, Sinemet, Sinemet CR)	Dopamine precursor	Orally disintegrating (Parcopa): 10/100 mg, 25/100 mg, 25/250 mg Immediate-release (Sinemet): 10/100 mg, 25/100 mg, 25/250 mg Controlled-release (Sinemet CR): 25/100 mg, 50/200 mg	Parcopa: 300–1,500 mg levodopa in divided doses Sinemet: 300–1,500 mg levodopa in divided doses Sinemet CR: 400–1,600 mg levodopa in divided doses	Anorexia, nausea, vomiting, orthostatic hypotension initially; vivid dreams, hallucinations, delusions, confusion, and sleep disturbances with chronic use
Entacapone (p. 421) (Comtan)	COMT inhibitor	T: 200 mg	200 mg 3–4 times/day up to maximum of 8 times/day (1,600 mg)	Dyskinesias, nausea, diarrhea, urine discoloration
Pramipexole (p. 980) (Mirapex, Mirapex ER)	Dopamine agonist	T: 0.125 mg, 0.25 mg, 0.5 mg, 1 mg, 1.5 mg ER: 0.375 mg, 0.75 mg, 1.5 mg, 2.25 mg, 3 mg, 3.75 mg, 4.5 mg	T: 0.5–1.5 mg 3 times/day ER: 0.375–4.5 mg/day	Nausea, drowsiness, lower extremity edema, postural hypotension, confusion, toxic psychosis (avoid use in pts with dementia)
Rasagiline (p. 1039) (Azilect)	MAO B inhibitors	T: 0.5 mg, 1 mg	0.5–1 mg once daily	Nausea, orthostatic hypotension
Ropinirole (p. 1076) (Requip, Requip XL)	Dopamine agonist	T: 0.25 mg, 0.5 mg, 1 mg, 2 mg, 3 mg, 4.5 mg XL: 2 mg, 4 mg, 6 mg, 8 mg, 12 mg	T: 3–8 mg 3 times/day XL: Up to 24 mg/day	Nausea, drowsiness, lower extremity edema, postural hypotension, confusion, toxic psychosis (avoid use in pts with dementia)
Selegiline (p. 1092) (Eldepryl, Zelapar)	MAO B inhibitor	C (Eldepryl): 5 mg OD (Zelapar): 1.25 mg	C: 5 mg with breakfast and lunch OD: 1.25–2.5 mg daily in the morning	Nausea, orthostatic hypotension
Tolcapone (Tasmar)	COMT inhibitor	T: 100 mg, 200 mg	100–200 mg 3 times/day	Dyskinesias, nausea, diarrhea, urine discoloration

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