Introduction to Psychopharmacology
Key concepts, drug classes, mechanisms, and clinical considerations
1. What Is Psychopharmacology?
| Aspect |
Description |
| Definition |
The scientific study of how drugs affect mood, cognition, behavior, and perception. |
| Goal |
To understand, develop, and use medications that treat mental‑health disorders safely and effectively. |
| Scope |
Includes basic neuroscience (receptor pharmacology, neurotransmitter systems) and clinical practice (prescribing, monitoring, side‑effect management). |
2. Fundamental Pharmacological Concepts
| Concept |
Key Points |
| Pharmacokinetics (PK) |
Absorption, distribution, metabolism, excretion (ADME). Determines drug concentration over time. |
| Pharmacodynamics (PD) |
Interaction of drug with its target (receptor, enzyme, transporter) → agonist, antagonist, partial agonist, inverse agonist. |
| Therapeutic Window |
Range between the minimum effective concentration and the concentration at which adverse effects appear. |
| Half‑life (t½) |
Time for plasma concentration to drop by 50 %; influences dosing interval. |
| First‑Pass Metabolism |
Hepatic metabolism that reduces oral bioavailability; important for drugs like propranolol. |
| Drug–Drug Interactions |
Enzyme induction/inhibition (e.g., CYP450), pharmacodynamic synergy, additive toxicity. |
3. Major Neurotransmitter Systems Targeted in Psychiatry
| System |
Primary Neurotransmitters |
Typical Clinical Effects of Modulation |
| Monoamine |
Serotonin (5‑HT), Norepinephrine (NE), Dopamine (DA) |
Mood regulation, anxiety, cognition, reward. |
| GABAergic |
Gamma‑aminobutyric acid (GABA) |
Inhibition, anxiolysis, anticonvulsant. |
| Glutamatergic |
Glutamate, NMDA receptors |
Excitation, learning, memory; dysregulation implicated in psychosis and depression. |
| Cholinergic |
Acetylcholine (ACh) |
Attention, memory, autonomic function. |
| Neuropeptide |
Substance P, CRF, neuropeptide Y |
Stress response, mood, pain perception. |
4. Core Drug Classes in Psychopharmacology
| Class |
Representative Agents |
Primary Indications |
Mechanism of Action (MOA) |
| Antidepressants |
SSRIs (fluoxetine), SNRIs (venlafaxine), TCAs (amitriptyline), MAOIs (phenelzine), atypical (bupropion) |
Major depressive disorder, anxiety, OCD, PTSD |
↑ Synaptic serotonin/NE (reuptake inhibition), ↑ dopamine (bupropion), ↓ monoamine breakdown (MAOIs) |
| Anxiolytics |
Benzodiazepines (diazepam), Buspirone, Hydroxyzine |
Generalized anxiety, panic, insomnia |
Benzos: Positive allosteric modulators of GABA‑A; Buspirone: 5‑HT1A partial agonist |
| Antipsychotics |
First‑gen: haloperidol; Second‑gen: risperidone, olanzapine, aripipraz |
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