List of Drugs Used in the Treatment Of Parkinson Disease / Parkinsonism

As we know that in Parkinsonism balance between cholinergic and dopaminergic neurons is disturbed. There is a loss of dopaminergic neurons. So we can achieve the balance again either by

Þ   Increasing the dopaminergic transmission

Þ   Or by decreasing the cholinergic transmission

Following Classes Of drugs are used in the Treatment of Parkinsonism

1.   Dopamine Precursor.

Þ   Levodopa.

Dopamine can’t cross blood-brain barrier but Levodopa can.

Levodopa is metabolized in the plasma and intestine by an enzyme called dopa decarboxylase. To inhibit this enzyme Levodopa is given in combination with Carbidopa

Carbidopa inhibits the dopa decarboxylase and increases the availability of Levodopa to the brain.

2.   MAO type B inhibitors.

Þ   Selegiline

Þ   Rasagiline

These Drugs inhibit the MAO type B enzyme which is responsible for the degradation of dopamine in the brain. Therefore, it increases the availability of dopamine in the substantia nigra.

3.   COMT inhibitor

Þ   Tolcapone

Þ   Entacapone

Catechol-O-Methyl Transferase (COMT) is an enzyme responsible for conversion of Levodopa into 3-O-Methyldopa. Although it is a minor pathway, when dopa decarboxylase is inhibited in the presence of Carbidopa this become major. And a sufficient quantity of Levodopa is metabolized and become useless by this pathway. Therefore Tolcapone or Entacapone is used to prevent this loss of Levodopa.

4.   Dopamine Receptor Agonists.

Þ   Bromocriptine

Þ   Apomorphine

Þ   Pramipexole

Þ   Ropinirole

Þ   Rotigotine.

These drugs stimulate the available dopamine receptors in the brain and thus useful in the treatment of Parkinsonism.

5.   Amantadine

This is an antiviral drug. It was accidentally discovered that this drug has additional anticholinergic, antiglutamate and dopamine-releasing effects.

All these combine effects are beneficial for treating Parkinsonism.

6.   AntiCholinergic Agents.

Þ   Benztropine

Þ   Trihexyphenidyl

Þ   Procyclidine

Þ   Biperiden

As we know that in Parkinsonism balance between cholinergic and dopaminergic neurons is disturbed. There is a loss of dopaminergic neurons. So we can achieve the balance again either by

Þ   Increasing the dopaminergic transmission

Þ   Or by decreasing the cholinergic transmission

Hence by using anticholinergics, we decrease the cholinergic transmission.