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Now after having discussed about the classification that is typical and as well as atypical antipsychotics now let me discuss the actions of the typical antipsychotics so if you take the actions of the typical antipsychotics remember these drugs they act by blocking the dito receptors and they differ significantly in their potency like we have low potency drugs
In typical antipsychotics and we have high potency drugs under typical antipsychotics but the basic mechanism of action of these drugs is these drugs they act by blocking the d2 receptors right these drugs they act by blocking okay so these drugs they act by blocking the d2 receptors and they differ significantly in their potency right now let me tell you the low
Potency drugs and as well as the high potency drugs now if you take the low potency drugs right you take this particular low potency drugs low potency drugs the example like what we have is chlorpromazine so remember chlorpromazine is a low potency drug what is the property of this particular low potency drugs is these low potency drugs they are highly sedative
Whereas the high potency drugs they cause very less sedation right they are highly sedative whereas you take the high potency drugs the high potency drugs or the high potency typical antipsychotics they cause less sedation alright next now a point that you should remember regarding the high potency drugs is they cause less sedation that is the advantage of these
High potency over the low potency drug but remember these high potency drugs are more likely to cause the extrapyramidal symptoms right one of the example of this high-potency drug is your haloperidol okay haloperidol is a high potency drug right now this particular high potency drug they are more likely to cause the extrapyramidal symptoms okay they are more
Likely to cause the extrapyramidal symptoms and this extra criminal symptoms are maximum with haloperidol right the extrapyramidal symptoms are maximum with haloperidol whereas this extrapyramidal symptoms are maximum with haloperidol this can be asked as a multiple choice question and extrapyramidal symptoms are least common with thioridazine right least common
With thioridazine okay so that is about your the extrapyramidal symptoms next let me tell you another very important point you take this high potency drug high potency drug they have very low anticholinergic and as well as the autonomic side effects as compared to the low potency drug right so these low potency drugs they have the anticholinergic and as well as
The autonomic side effects right anticholinergic and as well as autonomy side effects okay whereas you take with the high potency drugs high potency drugs they have low anticholinergic and autonomic side effects as compared to the low potency drugs right so these high potency drugs remember they have low anticholinergic and as well as the autonomic side effects
Okay next remember these high potency drugs they have very lower seizure threshold and these high potency drugs like your haloperidol or tyrosine can precipitate the convulsions in an epileptic patient right so another important point what you should remember is these high potency drugs they have very low seizure threshold right they have very lower caesar
Threshold so because they have very lower seizure threshold they can precipitate right they can precipitate convulsions okay so they can precipitate convulsions in epileptic patient right they can precipitate the convulsions in epileptic patients all right next another important point is all of these agents they are potent antiemetic drugs except thioridazine
So thyer it is in it is not it does not have the anti empty property whereas the other high potency drugs they have a potent antiemetic activity so one another important point what you should remember is these high potency drugs they have 4/10 antiemetic activity right in the sense these drugs they will reduce the vomiting of the individual except thioridazine
Right and this will be asked as a multiple-choice question because thioridazine does not have the antiemetic activities next you take this low potency drugs right low potency drugs the low potency drugs they possess the significant alpha blocking activity right they have right they have significant alpha blocking activity the maximum alpha blocking activity is
Seen with the chlorpromazine right chlorpromazine is a low potency drug this particular chlorpromazine it is having maximum alpha blocking activity so maximum is with chlorpromazine okay so low potency drugs they possess significant alpha blocking the maximum is with chlorpromazine and not only that this particular low potency drugs right this particular low
Potency drugs they also have the anticholinergic activity right anticholinergic activity but a point what you should remember here is you take this particular theory design thioridazine is the drug which is having maximum anticholinergic activity right it has maximum anticholinergic activity alright next now you take this particular high potency compounds so
High potency compounds they have less activity on these receptors that is one important point now due to blockade of the d2 receptors right what is the mechanism of action of these particular drugs they block the d2 receptors due to blockade of the d2 receptors in hypothalamus and as well as in the pituitary gland these drugs can increase the prolactin levels in
The individual and that will result in gallic toria and as well as amenorrhea right this is the important adverse effect with these particular drugs so remember these drugs by blocking d2 receptors in hypothalamus and as well as the pituitary gland what will happen if the d2 receptors are blocked which is nothing but the dopamine receptors when dopamine receptors
Are blocked there is increase in the prolactin secretion now what is the effect of the prolactin on the secretion of the milk the prolactin will increase the synthesis and secretion of the milk and what is the effect of the prolactin on the menstruation remember prolactin will reduce the levels of fsh and lh and thereby prolactin will cause amenorrhea if there is
Hyperprolactinemia in the female okay so remember this increased prolactin will cause galacto riya and as well as even amenorrhea right jarek toria and as well as even amenorrhea so this is the or these are the actions of the typical antipsychotics so remember these typical antipsychotics they act by blocking the d2 receptors right they differ in their potency
Into a low potency drugs and as well as the high potency drugs the low potency drugs example what we have is chlorpromazine which is a highly sedative drug whereas the high potency drug they cause less addition the examples what we have is the haloperidol and as well as thioridazine but the problem with this particular haloperidol or with your high potency drugs
They have the extrapyramidal symptoms and the maximum is with haloperidol and this extrapyramidal symptoms are least common with thioridazine and these drugs they have low anticholinergic and as well as the autonomic side effects and these drugs they have low seizure threshold so in epileptic patients they can precipitate the convulsions and let me tell you
Another important point these high potency drug they have potent antiemetic action except thioridazine and thyroidism remember it has maximum anticholinergic effect now you take the low potency drugs low potency drugs as i have said you already they are highly sedative they also have anticholinergic and as well as autonomic side effects and they have significant
Alpha blocking activity and the maximum is with your chlorpromazine now because of the blocking of the d2 receptors in hypothalamus and as well as the pituitary gland they will increase the prolactin level of the individual will result in gaelic toria and as well as amenorrhea by these particular drugs now let me discuss the actions of atypical antipsychotics
So if you see this atypical antipsychotics like these drugs they act by antagonistic action at 5ht two receptors right so if you take the mechanism of action of these drugs they have antagonistic action at 5ht to a receptors right now and remember these atypical antipsychotics these drugs they act by antagonistic action at 5-ht two air receptors and it these
Drugs they may or may not possess the d2 blocking activity right these drugs they may or may not possess the d2 blocking activity alright next now the point what you should remember here is they are not having they may or may not possess the d2 blocking activity that is the reason why these drugs they are less likely to cause they are less likely to cause the
Extrapyramidal symptoms whereas you take the typical antipsychotics the typical antipsychotics they were predominantly blocking the d2 receptors that is the reason why the extrapyramidal symptoms are very common with them very particularly with the high potency drug whereas you take the atypical like antipsychotics they may or may not possess the d2 blocking
Activity because there may or may not possess the d2 blocking activity that is the reason why they have less likely to cause the extrapyramidal symptoms right less likely to cause the extra criminal symptoms next another important point you see here most of these agents right most of these agents which one the atypical antipsychotics they will cause weight gain
They will cause hyperlipidemia and they will also cause the new onset diabetes mellitus so if you take the adverse effects of these drugs they can cause weight gain right they can cause weight gain they will also cause hyperlipidemia right they will also cause hyperlipidemia and the other one is new onset diabetes mellitus right new onset diabetes mellitus but
There is an exception most of your atypical antipsychotics they will cause weight gain hyperlipidemia and as well as new onset diabetes mellitus but there are certain drugs there are certain atypical antipsychotics which do not cause weight gain hyperlipidemia and as well as new onset diabetes mellitus the exceptions are ziprasidone right the exceptions are
Ziprasidone and then we have the aripiprazole right re-pipe resolved so remember except this ziprasidone and as well as aripiprazole they do not cause weight gain right these drugs they do not cause weight gain hyperlipidemia a new onset diabetes mellitus whereas the other drugs they will cause these adverse effects okay right so remember if you take the actions
Of atypical antipsychotics the mechanism of action is the antagonistic action at 5ht to a receptors they may or may not possess the d2 blocking activity because they may or may not possess the d2 blocking activity they are less likely to cause the extrapyramidal symptoms so these are the actions of the atypical antipsychotics
Transcribed from video
Anti psychotic Drugs Part 3 – Mechanism of action – CNS Pharmacology By Dr.G Bhanu Prakash Animated Medical Videos