Module 1.5.1 (Antipsychotics) Flashcards
What does increase activity in mesolimbic pathway cause?
–Delusions – Hallucinations – Other +ve Sx of schizophrenia.
What does decrease activity in the mesocortical pathway cause?
– Apathy – Withdrawal – Lack of motivation & pleasure – Other –ve Sx of schizophrenia.
What does inhibition of the nigrostriatal pathway cause?
Causes extrapyramidal SE of antipsychotic drugs
What does inhibiton of the tuberoinfundibular pthway cause?
Elevated serum prolactin levels
How do most antipyschotic drugs work?
Most antipsychotic drugs block dopamine receptors
- clinical dose is proportional to D2 receptor blockade
> Single positive electron tomography ligand scans show an increase in D2 receptors in nucleus accumbens of schizophrenia patients
Psychotic symptoms can be induced by drugs that increase dopaminergic activity. What drugs does this?
anti-parkinsonian agents
Drug-indcued parkinsonism is a common adverse effects of FGAs, it usually develops after weeks or months of treatment. What are these symptoms?
- Stooped posture
- Drooling
- Back rigidity
- Flexed elbows and wrists
- Tremors in the legs
- Slight flexed hip and knees
- Shuffling gait
- Reduced arm swing
- Hand tremor
Bradykinesia (slow movements)
Akinesia (immobility) has also been reported
> Usually develops after weeks or months of treatment.
> Usually reversible with anticholinergics
What drugs mimic positive symptoms?
- Amphetamine, methamphetamine (release dopamine & inhibit its reuptake) –> mimic positive symptoms
- Psilocybin, LSD (5-HT2A agonists) mimic positive symptoms
What drugs mimic positive, negative and cognitive symptoms?
Phencyclidine, ketamine (glutamate NMDA receptor antagonists)
What are atypical antispychotics?
(Second Generation Antipsychotics)
What are positive symptoms of schizophrenia? Why does this happpen?
Agitation Delusions Disorganised speech Disorganised thinking Hallucination Insomnia
- Due to excessive neuronal activity in mesolimbic neuronal pathway
What are negative symptoms of schizophrenia? Why does this happpen?
Apathy (avolition) Withdrawal Lack of motivation Lack of pleasure (anhedonia) Limited speech (alogia)
- due to insufficient activity in mesocortical neuronal pathway
What MOA + drug is used to treat negative and cognitive symptoms that results from deficient cortical dopamine activity?
Respond to 5HT2A receptor antagonism produced by SGAs –> increase dopamine release
mesocortical pathway
What MOA + drug is used to treat positive symptoms that results from excessive subcortical dopamine activity?
Respond well to D2 receptor antagonism produced by FGAs & SGAs
mesolimbic pathway
5HT2A antagonists increase dopamine release in the mesocortical pathways but what effects do they have on D2 antagonists?
5HT2A antagonist enhance / complements action of D2 antagonist to reduce positive symptoms
What do neagative and cognitive symyptoms respond to?
respond to 5-HT2A receptor antagonism produced by SGAs
What do positive symptoms respond to?
Positive symptoms respond well to D2 receptor antagonism produced by FGAs & SGAs
Antipsychotics require 1-3 weeks to stabilise the positive symptoms of schizophrenia. What are the three-time dependent changes in dpamine neurotransmission?
- Immediate effects: An increase in dopamine synthesis, release, and metabolism but NO therapeutic effect
- 2Prolonged effects (1-3 weeks): Depolarization blockade –> reduced dopamine release from mesolimbic and nigrostriatal neurons –>alleviate the positive symptoms of schizophrenia while causing EPSE
- Extended prolong effects: Dopamine receptor up-regulation and supersensitivity to dopamine agonists –> may contribute to the development of a delayed type of EPS called tardive dyskinesia
What are examples of first gen antipsychotics (typical)?
clue: CDFHPZ
- Chlorpromazine
- Droperidol
- Flupentixol
- Haloperidol
- Periciazine
- Zuclopenthixol
What are examples of second gen antipsychotics (typical)?
Clozapine
Olanzapine
Quetiapine
Risperidone
Paliperidone
Amisulpride
Aripiprazole
Asenapine (Saphris wafer)
Ziprasidone (Zeldox®)
Lurasidone
Brexipiprazole (new drug)
What are some differences between FGAs and SGAs?
FGA only effective for positive symptoms
SGA can alleviate positive and negative symptoms
- Incidence of extrapyramidal side-effects (less in the SGAs )
- Efficacy in treatment-resistant groups of patients
- Receptor selectivity
- Pharmacological properties