schizo – theory
1) dopamine theory: Amphetamine (overactive DA) produce similar sx to acute schizophrenia
* All antipsychotic drugs are D2 antagonists
2) 5HT theory: LSD (blocks 5HT) produce schizo sx
3) glutamate theory: ketamine (block NMDA receptor) produce schizo sx
5 schizo sx domains
1) +ve sx (abnormal behaviour)
2) -ve sx (substracted normal behaviour)
3) aggressive sx
4) ANX/ DEP
5) cognitive sx
DA pathways (1) DA theory
Nigrostriatal pathway (D1, D2)
- substantia nigra –> dorsal striatum
Mesolimbic pathway (D2, 3)
- ventral tegmental area (VTA) –> Limbic (emotional) brain
Mesocortical (D4)/ mesolimbic pathway
- ventral tegmental area (VTA) –> prefrontal cortex (emotional)
Tuberoinfundibular pathway (D3)
- hypothalamus –> anterior pituitary
Nigrostriatal pathway
substantia nigra –> dorsal striatum
Voluntary movement , prevent other movements
Mesolimbic pathway
ventral tegmental area (VTA) –> Limbic (emotional) brain
Reward and emotion
Mesocortical pathway
ventral tegmental area (VTA) –> prefrontal cortex
motion, cognition, attention
- Higher order thinking
- Executive functions
Tuberoinfundibular pathway (D3)
hypothalamus –> anterior pituitary (infundibular)
DA inhibits prolactin secretion into blood circ
1st vs 2nd gen
BOTH: block dopamine pathways = Control +ve sx of schizo
EPSE in 1st gen > 2nd gen
FGA eg
chlorpromazine
haloperidol
sulpiride
SGA eg
clozapine
olanzapine
quetiapine
risperidone
amisulpride
brexipiprazole
FGA SE
○ M1: dry mouth, constipation, blurred vision
○ H1: sedation, weight gain
○ A1: postural hypotension, dizzy
○ DA: EPSE, prolact
EPSE
EPSE description
SGA – atypical
produce less EPSE. more metabolic (-ine)
complex mixtures of actions:
diff SGA drug, diff receptor affinity – SE, efficacy
clozapine ADR
Clozapine-induced agranulocytosis
○ <1% of pt but fatal
○ Lack of granulocyte type WBC (monitor regular blood counts)
–> olanzapine (similar effect w/o this ADR)
drug-induced DM
clozapine, olanzapine, risperidone
(amisulpride exception)
MOA: unknown - may involve 5HT antagonism
* in hypothalamus
* in pancreatic beta cells
drug-induced weight gain
SGA: clozapine, olanzapine, risperidone
MOA: sedation (H1 antagonism) –> incr sedentary behaviour
maybe: A1 , 5HT2 antagonism on hypothalamus & feeding behaviour
WHY SGA < FGA EPSE
additional benefits of SGA
FGA: more on +ve sx control (not much for -ve sx, cognition and mood stability)
PK of APS and onset (tmax)
BAO
PK of APS and dosing freq (t1/2)
(divided dosing due to risk of hypoTEN, seizure)
most FGA, SGA
* long t1/2: OD dosing
eg haloperidol 12-36hrs
PO APS potency
HOR
low potency: sulpiride, chlorpromazine, Amisulpride, clozapine, quetiapine
high potency: risperidone (2-6mg), haloperidol, olanzapine (5-15mg)
dosing freq of LAI