High potency antipsychotics
This graphic shows the pharmacological activity of the classic antipsychotics. The receptor affinity profile of haloperidol is used as the representative of this class of agents. Haloperidol is relatively specific for the D2 post-synaptic receptor, and as such, doesn't have many side effects associated with the blockade of other receptors.
However, since the post-synaptic D2 receptor blockade is not in balance in the nigrostriatal tract, the classic antipsychotics are highly potent and are associated with significant extrapyramidal effects.
Haloperidol’s receptor affinity can best be described as D1, D2 > α1> 5-HT2A, M1.
Extra info: aloperidol's activity can best be described as D2 > α1> 5-HT2A, M1, haloperidol does not significant D1 activity.
High potency antipsychotics are the principle etiology of acute dystonias.
Extra info: High potency antipsychotics are the most common cause as they lack a counter balance of antagonism of the muscarinic receptor.
The 5-HT2A-antagonism activity of haloperidol is insufficient to overcome the D2 antagonism.
Extra info: Haloperidol's activity of 5HT2A antagonism is much too low to counterbalance its D2 antagonism.