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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

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