Final answer:
Selective D2 receptor antagonists like sulpiride are considered inadequate for antipsychotic treatment due to their narrow targeting of dopamine receptors. Effective antipsychotics, such as risperidone, antagonize multiple receptor types, which better manages the range of symptoms associated with psychotic disorders such as schizophrenia.
Step-by-step explanation:
Selective D2 receptor antagonists like sulpiride are considered unacceptable as antipsychotic agents because they lack the comprehensive pharmacological profile required to effectively treat all symptoms of disorders like schizophrenia.
Schizophrenia and similar psychotic disorders involve overactive dopamine neurotransmission, which is why antipsychotics are designed to block dopamine's effects by binding to its receptors without activating them. This action prevents dopamine from signaling information to adjacent neurons, thus mitigating symptoms.
However, effective antipsychotic medications, such as risperidone (Risperdal), not only antagonize D2 receptors but also serotonin type 2 (5HT2) receptors, and often have affinity for other receptor types, including adrenergic and histaminergic H1 receptors.
The broader receptor activity of risperidone contributes to its ability to reduce psychotic symptoms such as hallucinations, delusions, and disorganized thinking and also to influence other symptoms and behaviors associated with schizophrenia.
In contrast, selective D2 antagonists may not be sufficient in providing a comprehensive treatment for schizophrenia, possibly leading to less effective control of the full spectrum of psychotic symptoms or to an inadequate response in some patients.