Mechanism of Action: Neurotransmitter Modulation in Psychiatric
Medications
Submitted by
Sajid Bashir Shah
UW-23-Psy-MS-014
Submitted to
Sir Maaz
Department of Psychology
University of Wah
Wah Cantt
2024
I
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1. Anti-psychotics
1.1. First-generation (Typical) Antipsychotics
Mechanism of Action:
➢ These drugs primarily work by blocking dopamine D2 receptors in the brain.
(Stahl, 2013).
➢ By inhibiting dopamine transmission, they help to reduce symptoms of
psychosis such as delusions and hallucinations.
➢ Examples: Haloperidol, Chlorpromazine.
1.2. Second-generation (Atypical) Antipsychotics
Mechanism of Action
➢ These drugs block dopamine D2 receptors and serotonin 5-HT2A receptors.
➢ They have a broader mechanism of action compared to typical antipsychotics,
which can result in fewer side effects, particularly extrapyramidal symptoms
(movement disorders) (Muench & Hamer, 2010).
➢ Examples: Risperidone, Clozapine, Olanzapine.
2. Anxiolytics (Anti-anxiety medications):
2.1. Benzodiazepines
Mechanism of Action
➢ Benzodiazepines enhance the effect of the neurotransmitter gammaaminobutyric acid (GABA) at the GABA-A receptor.
➢ This leads to increased neuronal inhibition, resulting in sedative, hypnotic
(sleep-inducing), anxiolytic (anti-anxiety), anticonvulsant, and muscle relaxant
properties (Baldwin et al., 2013).
➢ Examples: Diazepam, Lorazepam, Alprazolam.
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2.2. Non-benzodiazepine Anxiolytics
Mechanism of Action
➢ These vary but often involve modulation of serotonin and/or dopamine
neurotransmission.
➢ For example, Buspirone, a common non-benzodiazepine anxiolytic, acts as a
partial agonist at serotonin 5-HT1A receptors.
➢ Unlike benzodiazepines, these drugs typically do not have sedative or musclerelaxant properties (Davidson, 2010).
3. Mood Stabilizers:
3.1. Lithium
Mechanism of Action
➢ Lithium's exact mechanism is not completely understood but is believed to
involve several mechanisms:
➢ Modulation of neurotransmitter release and reuptake.
➢ Inhibition of inositol monophosphates, affecting second messenger systems.
➢ Modulation of ion transport across cell membranes, particularly sodium and
calcium.
➢ It is effective in reducing manic episodes and stabilizing mood in bipolar
disorder (Malhi et al., 2017).
3.2. Anticonvulsants
Mechanism of Action
➢ These drugs are primarily used to treat epilepsy but also act as mood
stabilizers.
➢ They work by stabilizing neuronal activity through various mechanisms:
➢ Enhancing GABAergic (inhibitory) transmission (e.g., Valproate).
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➢ Inhibiting voltage-gated sodium channels (e.g., Carbamazepine).
➢ Inhibiting T-type calcium channels (e.g., Ethosuximide).
➢ The exact mechanisms for mood stabilization are not fully understood but are
thought to involve the regulation of neurotransmitter release and
neuroplasticity (Geddes & Miklowitz, 2013).
References
Baldwin, D. S., Aitchison, K., Bateson, A., Curran, H. V., Davies, S., Leonard, B.,
... & Wilson, S. (2013). Benzodiazepines: Risks and benefits. A
reconsideration. Journal of Psychopharmacology, 27(11), 967-971.
https://doi.org/10.1177/0269881113503509
Davidson, J. R. (2010). First-line pharmacotherapy approaches for generalized
anxiety disorder. Journal of Clinical Psychiatry, 71(Suppl 2), 24-29.
https://doi.org/10.4088/JCP.9058su1c.05
Geddes, J. R., & Miklowitz, D. J. (2013). Treatment of bipolar disorder. The Lancet,
381(9878), 1672-1682. https://doi.org/10.1016/S0140-6736(13)60857-0
Malhi, G. S., Tanious, M., Das, P., Coulston, C. M., & Berk, M. (2017). Potential
mechanisms of action of lithium in bipolar disorder.
Current
Understanding. https://doi.org/10.1007/s40263-017-0430-8
Muench, J., & Hamer, A. M. (2010). Adverse effects of antipsychotic medications.
American
Family
Physician,
81(5),
617-622.
https://www.aafp.org/pubs/afp/issues/2010/0301/p617.html
Stahl, S. M. (2013). Stahl's essential psychopharmacology: Neuroscientific basis
and
practical
applications.
Cambridge
https://doi.org/10.1017/CBO9781139626779.
University
Press.