ANTIPSYCHOTICS

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Now lets go through briefly about the drugs used in the treatment of SCHIZOPHRENIA

CLASSIFICATION OF ANTIPSYCHOTIC DRUGS: (1)

MECHANISM OF ACTION: (2)

There are two types of dopamine receptors.

D1 and D2.


D1 includes D1 and D5 receptors and D2 include D2, D3, and D4 receptors.

D2 receptors are the main targets for the antipsychotic activity. If the 80% of the D2 receptors get occupied, then it causes the antipsychotic activity. Drugs like chlorpromazine, haloperidol, flupentixol mainly bind to D2 receptors whem compared to the D1receptors. Whereas drugs like sulpiride and amisulpiride only antagonize D2receptors. Though clozapine has is not specific to Particular type of receptors, they have high capability to bind to the D4 receptors.


It is believed that the antipsychotic activity is because of the action of the drugs on the mesolimbic pathways and the motor effects that are not desired are because of the action of drugs on nigrostriatal pathways.

antipsychotic drugs takes some week to show their action even though they bind as soon as they are

administered.

EFFECTS OF THE DRUGS: (2)

The motor activity will be reduced with the use of antipsychotics and the animal does not respond to the even if it is kept in the environment which is unusual.

In case of human being, antipsychotics cause:

-anti emetic property is also shown

-displays less emotions

-patient can give the answers to the questions correctly

-Aggressive behavior will be stopped

Side effects:

There are two kinds of side effects that occur with the use of antipsychoticdrugs.

They are acute dystonias and tardive dyskinesia

On endocrine system: Neurons present in the tuberohypophyseal pathway liberate dopamine which is stops the prolaction secretion. So antiphychotics drugs administration disturbs this process and hence more amount of prolactin is produced which causes the breast
swelling and lactation not only in women but in men.

PHARMACOKINETICS: (2)

The levels of the antipsychotics in the plasma and their effect is not related. Hence the dose is determine with trail and error method. However we are lucky that the toxicity caused by these drugs is very less.

Plasma half life : 15 to 30 hours

Route of administration : oral route or IM injection

uSeS: (2)

Mainly used to treat schizophrenia


Conclusion: (2)

The antipsychotics are able to treat only70% of the patients where as the other 30% are called 'treatment resistant'patients. And they are unable to control the negative symptoms though they are effective against hallucinations and demulsions. Atypical antipsychotics are effective even the treatment resistant patients and can relieve from negative symptoms too. But they didn't overcome the side effects.

Reference:

1.Essentials of Medical pharmacology by KD Tripathi, 5th edition, Jaypee publishers, page no 391

2. Rang and Dales Pharmacology by Rang, Dale, ritter, moore, churchill Livingstone publishers, 6th edition, page no 545 to 555

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Author: Siva Mavuduru

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