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Antipsychotics Pharmacology
Ben Cunningham
14
Medical
Graduate
10/20/2010

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Term

Typical Antipsychotics

 

What do they act on in the CNS? (Give neuron, and 4 specific neuronal pathways)

Definition

They are dopamine D2 receptor blockers

 

Affected Dopaminergic Pathways:

1. Nigra-striatal

2. Mesolimbic

3. Mesocortical

4. Tubero-infundibular

Term

A. Nigro-Striatal Track

 

Function(s)?

Effects of low DA in this track?

Activity in schizophrenics?

Effect of typical antipsychotic on this track?

Definition

Track regulates movement

Low DA here = Parkinsonism

 

Nigrostriatal pathway functions normally in schizophrenics

 

Typical antipsychotic (D2 antagonist) acts on nigro-striatal path to cause Extra-pyramidal symptoms:

Parkinsonism

Akathisia

Dystonic reactions

Tardive dyskinesia is possible

Neuroleptic Malignant Syndrome

 

 

Term

 

B. Mesolimbic Pathway

 

Function(s)?

Activity in schizophrenics?

Effect of typical antipsychotic on this track?

 

Definition

Involved in pleasure sensations, drugs of abuse

 

Mesolimbic activity is HIGH in Schizophrenics:

Thought to mediate the positive symptoms of Schizophrenia (hallucinations)

 

D2 Antagonists (Typical Antipsychotics) cause a reduction in positive symptoms, but also unpleasant/uncomfortable mood (dysphoria) and lack of reward/pleasure response

 

 

Term

C. Mesocortical Pathway

 

Function(s)?

Activity in schizophrenics?

Effect of typical antipsychotic on this track?

Definition

Involved in emotional response and motivation

 

Mesocortical activity is low in untreated schizophrenics, responsible for the negative emotional/social/cognitive symptoms

 

Typical antipsychotics decrease DA, so they further lower mesocortical activity, making negative symptoms worse!

Term

D. Tuberoinfundibular pathway

 

Function(s)?

Activity in schizophrenics?

Effect of typical antipsychotic on this track?

Definition

Normal function is to inhibit the release of prolactin

Pathway is normal/unaffected in schizophrenics

 

typical antipsychotics results in hyperprolactinemia, w/ assoc. side effects:

galactorrhea

amenorrhea

sexual dysfunction

Term

Antipsychotics/Neuroleptics

 

Extra-pyramidal symptoms

 

Cause/pathway affected

3 acute levels of symptoms

1 late-onset symptom

Definition

Caused by antipsychotics blocking DA nigro-striatal pathway

 

Acute:

Dystonia within 4 hours (muscle spasm, stiffness, oculogyric crisis)

Parkinsonism within 4 days (parkinsonian symptoms)

Akathisia within 4 weeks (restlessness)

 

Late Onset:

Tardive Dyskinesia:

usually after 4 months

Involuntary repetitive movements,

generally irreversible

Term
What can you give to treat each of the EPS symptoms?
Definition

Dystonia - give anticholinergics

Akathisia - give anticholinergics or beta blockers

Parkinsonism - anticholinergics, or

amantadine (a DA agonist) - because Dopamine suppresses Ach effects

Term

Antipsychotics

 

Anticholinergic side effects (5)

Definition

Constipation

Dry mouth

Blurred vision

Drowsiness

Confusion/Impaired cognition

Term

Antipsychotics

 

Antihistaminergic side effects (2)

Definition

Weight gain

Drowsiness

Term

Antipsychotics

 

Anti-alpha adrenergic side effects (3)

Definition

Decreased BP

dizziness

drowsiness

Term

 

Antipsychotics

 

Describe the general side effects of low potency vs. high potency drugs

 

Give an example of a high/mid/low potency drug

 

Definition

Low potency, have to increase the dose to get effective anti-dopamine effect, results in non-specific neuro side effects (Anticholinergic/histaminergic/alpha-adrenergic)

 

High potency will result in EPS side effects and Prolactin elevation (both directly due to low dopamine)

 

High = Haloperidol

Mid = Perphenazine (like Purgatory)

Low = Chlorpromazine (like chlorine that's down in the pool)

Term

Atypical Antipsychotics

 

Closapine:

3 indications for use

How is it therapeutic?

Significant side effect(s)?

Definition

Indications:

1. treatment-resistant schizophrenia

2. schizophrenia w/ tardive dyskinesia

3. schizophrenia or schizoaffective disorder w/ recurrent suicidal behavior

 

Therapeutic value:

Treats positive symptoms, and improves negative/cognitive symptoms as well

Also, much lower incidence of EPS and TD

 

Side effect: Agranulocytosis, a life-threatening drop in WBC count

Dont use if you have a pre-existing blood disorder, and blood monitoring the entire time patient is on the drug

Term

 

Atypical Antipsychotics

 

What is the role of serotonin in the action of these drugs?

 

Definition

Serotonin inhibits the effects of dopamine in some places (i.e. the Nigro-striatal tract)

...so 5HT inhibition by atypical antipsychotics will increase dopamine in the nigrostriatal, resulting in a decrease in EPS symptoms

 

(and Serotonin doesn't act in the mesocortical and mesolimbic pathways, so the anti-DA effects still occur here as in treatment with typical neuroleptics)

Term

 

Atypical Antipsychotics

 

Arapiprazole - Brand name?

what type of drug is it?

 

Mech/Idea behind its therapeutic action?

 

Side effects?

 

How does it compare with other atypicals (like clozapine and olanzapine)

 

Definition

Abilify

Its a D2 partial agonist (its also a 5HT antagonist)

 

As a partial agonist, arapiprazole reduces the stimulation of the mesolimbic pathway (reducing pos symptoms), provides some stim to the mesocortical pathway (reduce neg symptoms), and does not overstimulate the nigrostriatal pathway (so no EPS)

 

Side effects are Metabolic:

Weight gain

Hyperlipidemia

Hyperglycemia, diabetes, ketoacidosis

 

araprazole treatment results in less metabolic side effects than clozapine or olanzapine, but may also be less efficacious

(olanzapine is most effective and worst for wt gain)

 


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