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:
- Nigrostriatal
- Mesocortical
- Mesolimbic
- Tuberoinfundibular
Also present in the chemoreceptor trigger zone.
Two neurotransmitters are involved:
- Dopamine -inhibitory
- Acetyl choline –excitatory
Decrease in dopamine and increase in cholinergic activity leads to various symptoms.
Features
- Tumors at rest
- Rigidity
- Hypokinesia/bradykinesia (difficulty in initiating movement) /akinesia
- Flexed posture
- Short steps
- Excessive salivation due to cholinergic fibers
Etiology
- Idiopathic nigrostriatal degeneration most common
- Infections e.g. encephalitis
- Atherosclerosis (CVA)
- Drugs
- Antipsychotics –block dopamine receptors
- Reserpine
- 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