•WHAT IS PARKINSONISM DRUGS:-
Parkinsonism is an extrapyramidal motor disorder. It is characterized by rigidity, tremor, and hypokinesia. Secondary manifestations, like excessive salivation, changes in mood, and dementia, may also occur.
• How many types of Classification of drugs
A. Drug affecting brain dopaminergic system
1. dopaminergic system a). Levodopa
2. Decarboxylase inhibitors
a) Carbidopa
b) Benzserazide
3. Dopaminergic agonists
a). Bromocryptine
b). Ropinirole
c). Pramipexole
4. MAO- B inhibitor
a). Selegiline
5. Dopamine facilitator
a). Amantadine
B. Drugs affecting brain cholinergic system
1. Central anticholinergic a). Trihexyphenidyl b). Benztropine
c). Procyclidine
2. Antihistaminics
a). Promethazine
b). Orphenadrine
• what is LEVODOPA:-
It is a precursor of dopamine. It acts by getting converted into dopamine. Dopamine by itself is not helpful since it does not cross the blood-brain barrier.
Decarboxylase inhibitors like carbidopa and benserazide are given with levodopa. They decrease the peripheral decarboxylation of levodopa. So, more levodopa can enter the brain for getting converted into dopamine.
• Actions of LEVODOPA:-
1. Levodopa tremorInitially is there also improves relief. Is relief all from the manifestations of rigidity and hypokinesia? Of pParkinsonismLater
Tremor is also relieved.
2. Levodopa is ineffective in drug-induced parkinsonism
3. The peripherally formed dopamine can cause tachycardia by acting on beta-adrenergic receptors.
4. Peripherally formed dopamine can act on the CTZ, producing nausea and vomiting.
5. Also, levodopa inhibits prolactin secretion.
• What is the Adverse effect of levodopa :
1. Nausea and vomiting
2. Postural hypotension
3. Cardiac arrhythmias
4. Exacerbation of angina
5. Alteration of taste sensation
6. On-off phenomenon (alternative phases of response and no response).
• What is CARBIDOPA and BENZSERAZIDE :
They are peripheral decarboxylase inhibitors. They prevent the peripheral decarboxylation of levodopa. So more levodopa enters the brain for getting converted into dopamine.
• What is the Advantages of CARBIDOPA and BENZSERAZIDE
1. The t/2 of levodopa is increased, and so the dose is decreased.
2. Systemic concentration of dopamine is reduced, so nausea and vomiting are less.
3. Cardiac toxicities are reduced.
4. On-off effect is minimized.
5. Degree of improvement is higher.
• WHAT IS BROMOCRYPTINE :
It is an ergot derivative. It is a dopaminergic agonist—improvement in pParkinsonismoccurs within 30 to 60 minutes after oral administration. The effect lasts for 6 to 10 hours. It is effective in patients who do not respond or are resistant to levodopa. It inhibits prolactin release.
• WHAT IS Adverse effects:-
Nausea, vomiting, postural hypotension, insomnia, hallucinations, nasal stuffiness, and cardiac arrhythmias.
• WHAT IS SELEGILINE :
It is a selective MAO-B inhibitor. It leads to the accumulation of dopamine in the brain by preventing its breakdown. When used in early cases, it retards the progression of symptoms. Commonly it is used with levodopa to prolong its action. The clinical benefit of selegiline is short (6 to 24 months).
• Advantage:
Absence of hypertensive crisis (cheese phenomenon) with levodopa or tyramine.
• WHAT IS AMANTADINE :
It is an antiviral agent effective in parkinsonism. It increases the synthesis and release of dopamine and inhibits its neuronal uptake. Also, it has some anticholinergic effects. It is less effective than levodopa. Dose: 100 mg twice daily.
• Adverse effects :
Insomnia, confusion, hallucinations, dizziness, and nightmares. Also, livedo reticularis and ankle edema (due to local release of catecholamines which produce vasoconstriction).
• WHAT IS CENTRAL ANTICHOLINERGICS :
The central anticholinergics used in pParkinsonismare trihexyphenidyl, benztropine, and procyclidine. They are effective in drug-induced parkinsonism.
They improve termor but are less effective in reducing rigidity and hypokinesia.
•Adverse effects: dry mouth, blurred vision, amnesia. Confusion, nightmares, hallucination, increased intraocular pressure, and constipation.
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