Pharmacology of Antipsychotics(Neuroleptics)

Question 1

Describe Schizophrenia

Answer 1

A type of psychosis characterised by *delusions, hallucinations and thought disorder(positive symptoms) together with social withdrawal, blunted emotional responses (negative symptoms)

Question 2

Describe the drug treatment of Schizophrenia

Answer 2

DRUG TREATMENT
Neuroleptics/Antipsychotics drugs
>Block postsynaptics dopamine D2 receptors, which has antipsychotic actions
>Most neuroleptics also block cholinergic, alpha-adrenergic, serotonin and histamine receptors leading to corresponding side effects.

Question 3

Classify Neuroleptics

Answer 3

*Typical/Conventional Antipsychotics: First-Generation
1. Phenothiazines (Chlorpromazine, Fluphenazine)
2. Butyrophenones (Haloperidol)
3. Thioxanthenes (Flupenthixol)
These drugs act primarily by blocking D2 receptors

*Atypical/Second-generation Antipsychotics:
Include Clozapine etc
MOA: Block dopamine receptors more selectively than conventional antipsychotics.
> Less likely to cause extrapyramidal side effects
> Increase prolactin release slightly (except risperidone)

Question 4

Describe the Extrapyramidal Side Effects

Answer 4

Blockade of dopamine receptors may cause:
> Parkinsonism, especially in older patients; tardive dyskinesia, akathisia, hyperprolactinaemia
> Parkinsonian symptoms relieved by administration of antimuscarinic drugs.

Question 5

Describe the effects, dose and A/E of Chlorpromazine

Answer 5

Low potency: blockade of D2 receptors
Effects:
> Improves disturbed thought and blunkted effect
> Changes withdrwal and autistic behaviour
> Reduces Hallucinations
> Effective for restless aggressive patients and patients who are difficult to control.
Dose
>Initiate with 25mg tds po, increase gradually until symptoms are controlled
>Usual maintenance dose is 75 to 300mg
Adverse Effects
Extrapyrimidal symptoms include parkisonism(seldom), anticholinergic effects, sedation, weight gain

Question 6

Describe the MOA, Dose and A/E of Haloperidol

Answer 6

MOA: The most potent D2 antagonist, blockade of D2 receptors»5HT2A,
used for both **acute and chronic schizophrenia. **

Dose
> 5-10 mg IM or PO, repeat 4-6 hours
> Common maintanance dose 4mg at bedtime

Adverse Effects
Akathisia(motor restlessness), extrapyramidal symptoms, anticholinergic effects.

Question 7

Describe the MOA, Indications, Dose and Adverse Effects of Clozapine

Answer 7

MOA: Weak D2-receptor antagonist
Indications
>Used in patients unresposnive to other antipsychotics
>Improves both the negative and positive symptoms
>Has few or no motor A/E
>minimal risk of causing tardive dyskinesia.
Dose
>12.5 mg PO OD or BD, increased daily in increments of 25

Adverse effects
Increased salivation, occasioanlly convulsions, sedations, hypotension, tachycardia, weight gain, agranulocytosis

Question 8

Descrribe Depot Antipsychotic Drugs (Agents, PK Dosages and A/E)

Answer 8

Depot Antipsychotic Drugs are slow-acting/ slow-release form of antipsychotics.

PK: Long-Acting

Agents
1. Haloperidol deconoate: 25 tp 150 mg IM q 28 days
2.
2. Fluphenazine Decanoate: 12.5 to 50 mg IM q 2-4 weeks

A/E: Higher incidence of Extrapyramidal side effects than oral medication.