Pharmacology - antipsychotics Flashcards
Antipsychotic method of action
D2 antagonist - Reduced level of dopamine activity at the D2 receptor
Dopamine receptors
Targetted pathways:
- Mesolimbic
- Mesocortical
Unwanted effects:
- Nigrostriatal - movement
- Tuberoinfundibular - HPA (prolactin)
Typical antipsychotic side effects
Sedation Extrapyramidal side effects Weight gain QTc prolongation Dizziness Sexual dysfunction
Acute Dystonic Reaction
Abnormal muscle tone resulting in muscular spasm and abnormal posture
- oculogyric crisis
- torticollis
Oculogyric crisis
Eyes point involuntarily upwards + hyperextended neck
Typical antipsychotics
- Older
- More likely to cause extrapyramidal side effects
- Bind more to muscarinic and histaminic receptors
Atypical antipsychotics
- Serotonergic activity
Examples of typical antipsychotics
Haloperidol Fluoenthixol Zuclopenthixol Chlorpromazine Sulpride
Examples of atypical antipsychotics
Clozapine Olanzapine Risperidone Quetiapine Amisulpride Aripiprazole - most tolerable
Aripiprazole
D2 partial agonist not an antagonist
Extrapyramidal side effects (EPSEs)
Parkinsonism:
- Bradykinesia
- Muscle stiffness
- Tremor
- Tardive dyskinesia
- Akathisia
- Acute dystonia - oculogyric crisis
Atypical antipsychotic side effects
Weight gain
Dyslipidaemia
Diabetes
Antipsychotic monitoring
Baseline - FBC, Lipids, HbA1c, Weight, ECG, BP and pulse
Weekly - weight (ideally but not in practice)
3 months - FBC, Lipids, HbA1c, Weight, ECG, BP and pulse
Yearly - FBC, Lipids, HbA1c, Weight, ECG, BP and pulse
Neuroleptic malignant syndrome
Rare and life-threatening rection to antipsychotics
- fever
- confusion
- muscle rigidity
- sweating
- autonomic instability
Cause of death due to neuroleptic malignant syndrome
Rhabdomyolysis
Renal failure
Seizures
Risks of neuroleptic malignant syndrome
High potency antipsychotics (typical)
Antipsychotic niave
High dose
Young men
Treatment of neuroleptic malignant syndrome
- Emergency referral to A&E
- Stop antipyschotics
- Give benzodiazepines for behavioural disturbance
- Fluid restriction
- Reduce temperature - cooling
- Oxygen - if necessary
- Rhabdomyolysis - fluids and sodium bicarbonate
- Relax muscles - dantrolene or lorazepam and 2nd line bromocriptine
How to treat an acute dystonic reaction
Procyclidine - anticholinergic
Clozapine side effects
- Agranulocytosis/ neutropenia - monitor FBC
- Sedation
- Myocarditis - ECG
- Arrhythmia
- excessive salivation
- weight gain
- constipation
- glucose intolerance
Treatment for tardive dyskinesia
Tetrabenazine
If clozapine doses are missed for 48+hrs
The dose will need to be restarted again slowly
Smoking and clozapine
Smoking speeds up the metabolism of clozapine so smoking cessation can cause clozapine toxicity
Torticollis
Unilateral neck pain, spasm and restricted range of movement
