Classify the anti-psychotic drugs (25% marks).
Outline the pharmacology of haloperidol (75% marks).
Excellent answers were able to provide a classification of antipsychotics based on either typical/atypical
or first/second generation categories, provide examples of each and identify key differences in
mechanism and effects. They also distinguished between butyrophenones and phenothiazines within the
typical antipsychotic group. Haloperidol was identified as a butyrophenone, with description of
pharmaceutics, dose and route, as well as pharmacodynamics and pharmacokinetics. Key adverse
effects were detailed, focusing on those specific to haloperidol, including a description of different types
of extrapyramidal symptoms and QT prolongation/ torsades de pointes.
For 20% of the marks, you would really only need to do something like this:
As for haloperidol:
|Routes of administration||Oral, IV, IM, s/c|
|Absorption||Rapidly and completely absorbed; oral bioavailability is about 60%|
|Solubility||pKa 8.66; minimally water-soluble|
|Distribution||VOD=18L/kg; 92% protein-bound|
|Target receptor||D2 receptors, as well as muscarinic cholinergic receptors, histamine receptors and alpha-adrenergic receptors|
|Metabolism||Hepatic metabolism into inactive metabolites|
|Elimination||Inactive metabolites are renally cleared|
|Time course of action||Elimination half-life of 14-36 hours|
|Mechanism of action||Antipsychotic effects are mediated mainly by the D2 antagonist effect on the dopaminergic neurons in the mesolimbic system|
|Clinical effects||Sedation (antihistamine effect).
Extrapyramidal side effects (dystonia, oculogyric crisis, laryngospasm, akathisia, rigidity, parkinsonism and tardive dyskinesia)
Hyperprolactinaemia (dopamine blockade)
Postural hypotension and sexual dysfunction (α-adrenergic receptor blockade)
Anticholinergic side effects (xerostomia, urinary retention, tachycardia, constipation, blurred vision, tachycardia and delirium)
Lowered seizure threshold
QT interval prolongation
|Single best reference for further information||Tyler et al (2017)|
Fischer-Barnicol, David, et al. "Typical and atypical antipsychotics–The misleading dichotomy." Neuropsychobiology 57.1-2 (2008): 80-87.
Sadek, Joseph. "Antipsychotics." Clinician’s Guide to Psychopharmacology. Springer, Cham, 2021. 113-145.
Zareba, Wojciech, and David A. Lin. "Antipsychotic drugs and QT interval prolongation." Psychiatric quarterly 74.3 (2003): 291-306.