CNS Part- 2
In comparing side effects profiles of chlorpromazine and haloperidol, we find that haloperidol tends to cause or is associated with which of the following?
|A||Higher incidence of extrapyramidal reactions|
|B||Intense atropine – like side effects|
|C||More frequent and lethal blood dyscrasias|
|D||More frequent orthostatic hypotension|
a. It is common to classify chlorpromazine and other phenothiazine antipsychotics as “low potency” agents, in comparison with haloperidol (butyrophenone class), which has been called “high potency” Potency, of course, usually refers to the dose needed to cause a stated effect of a certain intensity In that regard, haloperidol is more potent than phenothiazines and is more selective for blocking dopamine D2 receptors.
b. But another implied meaning of using this term is that chlorpromazine and other “low potency” agents tend to cause a higher incidence of peripheral autonomic side effects (from α blockade and antimuscarinic effects) than haloperidol; and a lower incidence of extrapyramidal reactions, which can be severe and of sudden onset with haloperidol—a very rapidly acting drug, especially when given parenterally (as for acute psychosis).