Antipsychotic drugs Flashcards
(50 cards)
antipsychotic targeting implications
-multiple receptors targeted w benefit
-unable to predict efficacy
-need to individualize tx based on response
-multiple receptors = more side effects = poor adherence
Autonomic antipsychotic mech and side effects
-muscarinic cholinoceptor blockade:
-dry mouth
-constipation
-difficulty urinating
-alpha block:
-orthostatic hypotension
CNS antipsychotic mech and side effects
-dopamine block: PD, akathasia, dystonias
-supersensitivity of DA receptors: tardive dykinesia
-muscarinic block: toxic-confusional state
-histamine block: sedation
Typical (1st gen) antipsychotic drugs
-phenothiazines (chloropromazine)
-butyrophenones (haloperidol)
Typical antipsychotics MOA
-strong D2 ANTAgonists
-affect mesolimbic system
-D1 antagonists not effective
slide 5
typical antipsychotic clinical features
-effective in positive symptoms
-extrapyramidal sx side effect
-risk of tardive dykinesia after months/years of tx
typical antipsychotic structure (chlorpromazine)
-phenothiazine nucleus
-3 ring in row, middle one not aromatic and has N on bottom S on top
Phenothiazine drugs
-chlorpromazine
-promazine
-triflupromazine
Chlorpromazine (phenothiazine)
-first drug that worked well
-D2 antagonist w 5HT2A activity
-multiple undesired targets (dirty drug) (antihistamine)
-no longer first line
Butyrophenone drugs
-haloperidol
-droperidol +/- fentanyl
-aromatic ring w F on one end and chain with 2 rings at other end
Haloperidol
-butyrphenone
-more selective D2 ANTAgonist than chlorpromazine
-no longer first line bc EPS
Delayed onset of typical antipsychotics
-takes days to weeks
-delay phase: block D2 receptors, initially offset by D2 antagonism
-antagonism phase: D2 internalized (desensitization) and D2 autoreceptors respond better to DA inhibitory effect (sensitation)
-post-synaptic vs pre-synaptic?
-
slide 9 idk
De
Delay phase
-blockade at postsynaptic D2 receptors, initially offset by
antagonist binding to D2 autoreceptors
-dopamine metabolites inc initially after start of antipsychotic tx
-graph is bell curve
antagonism phase
-D2 internalized (desensitization) and D2 autoreceptors respond better to DA inhibitory effect (sensitation)
-post-synaptic vs pre-synaptic?
-as dopamine metabolite levels dec, efficacy inc
-graph is line inc
Actions of D2 antagonists in different brain regions
-mesolimbic : primary tx effects!!!
-basal ganglia: motor, EPS
-mesocorticol: hypofunction in scz, antagonists may cause cognitive deficits
-hypothalmus and endocrine: hyperprolactinemia
-medulla: chemoreceptor trigger zone, anti-emetic
Receptor occupancy of antipsychotics
-determines balance between tx effects and EPS
-70-80% receptor occupancy ideal
->80% = EPS
Movement disorders induced by D2 antagonists
-EPS
-tardive dyskinesia
-neuroleptic malignant syndrome (NMS)
Extrapyramidal Symptoms (EPS)
-30-50% pt will experience
-days/weeks after initiation
-reversible
-dystonia (inc muscle tone)
-pseudoparkinsonism (muscle rigidity)
-tremor
-akathisia (restlessness)
Drug therapy for EPS
-anticholinergics: benztropine, trihexyphenidyl, akineton
-antihistamines: diphenhydramine
-amantadine (dopamine releasing agent)
-beta blockers: propranolol for akathisia
Neurons involved in EPS
-nigrostriatial pathway
-excitatory amplified and inhbitory diminished under D2 antagonism
Tardive Dykinesia sx
-late
-IRREVERSIBLE
-rhythmic involuntary movements of the mouth
-choreiform movements: irregular purposelessness (HD)
-athetoid (worm-like) movements
-axial hyperkinesias (to and fro movements
Tardive Dykinesia MOA
-not well understoof
-maybe adaptive response, antagonist supersensitivity of receptors to dopamine?