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  1. Amisulpride :
    1. It is a D2/D3 dopamine receptor antagonist with well-characterized atypical antipsychotic properties.
    2. It has a role in negative symptoms as lower doses that is upto 200 mg and effective in positive symptoms in doses in more than 200 mg.
  2. Paliperidone:
    1. Paliperidone is a dopamine antagonist of the atypical antipsychotic class of medications.
    2. It is an extended release formulation of paliperidone that uses the OROS extended release system to allow for once-daily dosing.
    3. Paliperidone palmitate is a long-acting injectable formulation of paliperidone palmitoyl ester indicated for once-monthly injection after an initial titration period.
Paliperidone is the primary active metabolite of the older antipsychotic risperidone.
Mechanism of Action
  1. The proposed therapeutic activity of the drug in schizophrenia is mediated through a combination of :
    1. Central Dopamine Type 2 (D2)
    2. Serotonin Type 2 (5HT2A) receptor antagonism.
  2. With additional affinity for antagonism of histaminic (H1) and adrenergic receptors (1 & 2)
  3. BUT, it has no affinity for the Muscarinic-Cholinergic receptors or â1 and â2 adrenergic receptors
Side effects
The most common side effects of paliperidone are restlessness and extrapyramidal disorder, including involuntary movements, tremors and muscle stiffness.
  1. Asenapine
    Asenapine is an atypical antipsychotic developed for the treatment of schizophrenia and acute mania associated with bipolar disorder.
Asenapine shows high affinity for numerous receptors, including the serotonin receptors, the adrenergic receptors, the dopamine receptors, and the histamine H1 and H2 receptors.
It is used for the acute treatment of adults with schizophrenia and acute treatment of manic or mixed episodes associated with bipolar I disorder with or without psychotic features in adults.
Side effects
Common side effects: Severe akathisia, oral hypoesthesia, somnolence, dizziness, extrapyramidal symptoms other than akathisia, weight gain, insomnia, extreme sedation, headache.
Rare side effects: Neuroleptic malignant syndrome (Combination of fever, muscle stiffness, faster breathing, sweating, reduced consciousness, and sudden change in blood pressure and heart rate.), tardive dyskinesia.
  1. Tiapride
    1. It is a drug that selectively blocks D2 and D3 dopamine receptors in the brain.
    2. It is used to treat a variety of neurological and psychiatric disorders including dyskinesia, alcohol withdrawal syndrome, negative symptoms of psychosis, and agitation and aggression in the elderly.
  1. In alcoholic patients studies have found that tiapride has anxiolytic effects.
  2. Dopamine hyperactivity has been linked with alcohol withdrawal syndrome (AWS), suggesting that tiapride’s antidopamingergic effects are the most likely mechanism for its clinical efficacy.
Side effects
  1. Although it is considered a “safe” medicine, it is, like sulpiride, strictly contraindicated for patients under the age of 18 due to its effects during the process of puberty.
  2. Tiapride causes excess prolactin levels in plasma, which can cause decreased libido, infertility and increased risk of breast cancer.
  3. Other side-effect are rhabdomyolysis & Cardiac abnormalities such as prolongation of the QT interval and torsades de pointes have also been observed.
  1. Clozapine
    1. In addition to being a dopaminergic antagonist (weaker than the typical neuroleptics), this atypical antipsychotic is a 5-HT2A/2C blocker.
    2. Blockade of cerebral 5-HT2A/2C receptors may account for its efficacy in resistant cases of schizophrenia.
    3. Olanzapine is also a similar atypical antipsychotic drug.
  2. Risperidone
    1. This recently developed atypical antipsychotic is a combined 5-HT2A + dopamine 2 antagonist, similar to clozapine.
    2. Like the latter, it specially ameliorates negative / symptoms of schizophrenia and produces extrapyramidal side effects only at higher doses.

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