Drugs Used in Parkinsonism -An Introduction

Parkinson’s disease/Parkinsonism

Disease of old people after about 60 years of age. 1 in 200 elderly are affected. Mainly due to decrease in dopamine in dopaminergic pathways:

1. Nigrostriatal
2. Mesocortical
3. Mesolimbic
4. Tuberoinfundibular

Also present in the chemoreceptor trigger zone.

Two neurotransmitters are involved:

1. Dopamine -inhibitory
2. Acetyl choline –excitatory

Decrease in dopamine and increase in cholinergic activity leads to various symptoms.

Features

1. Tumors at rest
2. Rigidity
3. Hypokinesia/bradykinesia (difficulty in initiating movement) /akinesia
4. Flexed posture
5. Short steps
6. Excessive salivation due to cholinergic fibers

Etiology

• Idiopathic nigrostriatal degeneration most common
• Infections e.g. encephalitis
• Atherosclerosis (CVA)
• Drugs

1. Antipsychotics –block dopamine receptors
2. Reserpine
3. Alpha methyl dopa

• Poisoning (Wilson’s disease) –deposition of copper in basal ganglia

Classification

Drugs that increase dopaminergic activity

Dopamine precursor

Levo dopa

Peripheral dopa – decarboxylase inhibitors

Sinemet: levodopa+carbidopa (10:1)

(100 -250mg)          (10 -25 mg)

Madopar: levodopa+benserazide (4:1)

(50 -200mg)     (12.5 -50 mg)

Dopamine releasing drugs

Amantadine (100mg)

Dopamine receptor agonists

Ergot derivatives

Bromocriptine

Lisuride

Pergolide (0.5mg – 3mg/day)

Non ergot derivatives

Pramipexole (d3 agonist) (0.125mg – 0.5 -1.5mg)

Ropinirole (0.25mg – 2 – 8mg)

Apomorphine (2 – 8mg)

Selective COMT inhibitors

Tolcapone (100mg tds) nitrocatechol derivative

Entacapone (200mg tds)

MAO-b inhibitors

L-deprenil (selegiline) (5 – 10mg)

Rasagaline

Drugs that decrease cholinergic activity

Central anticholinergics

Benzhexol (2-20mg)

Benztropine (0.5 mg – 6mg)

Procyclidine, (7.5 – 30 mg)

Biperiden (1mg – 20 mg)

Antihistamines with anticholinergic activity

Orphenadrine (200 – 400 mg)

Diphenhydramine (25 – 100 mg)

Continue Reading

Levo Dopa

Peripheral DOPA decarboxylase inhibitors and Dopamine Releasing Drugs

Dopamine Receptor Antagonists

Drugs Decreasing Cholinergic Activity