Here is the complete, textbook-grounded guide:
Psychiatric Pharmacology: Major Drug Classes
1. 🧠 ANTIPSYCHOTICS
Introduction
Antipsychotic drugs reduce psychotic symptoms across a wide variety of conditions — schizophrenia, bipolar disorder, psychotic depression, dementia-related psychoses, and drug-induced psychoses. They work primarily by blocking dopamine (D₂) receptors in the brain. There are two generations:
- First-generation (typical/conventional) — e.g., haloperidol, chlorpromazine. Highly effective but cause significant extrapyramidal side effects (EPS) such as dystonia, akathisia, and tardive dyskinesia.
- Second-generation (atypical) — e.g., clozapine, olanzapine. Block both dopamine and serotonin (5-HT₂) receptors, causing fewer EPS and now being the most widely used. They also improve mood and reduce anxiety.
(Katzung's Basic and Clinical Pharmacology, 16th Ed.)
5 Common Antipsychotic Drugs
| Drug | Class | Key Use | Notable Side Effects |
|---|
| Haloperidol (Haldol) | 1st generation (typical) | Schizophrenia, acute agitation | High EPS, tardive dyskinesia |
| Chlorpromazine (Thorazine) | 1st generation (typical) | Schizophrenia, nausea, hiccups | Sedation, photosensitivity, EPS |
| Clozapine (Clozaril) | 2nd generation (atypical) | Treatment-resistant schizophrenia | Agranulocytosis (requires WBC monitoring), weight gain |
| Olanzapine (Zyprexa) | 2nd generation (atypical) | Schizophrenia, bipolar mania | Weight gain, metabolic syndrome, sedation |
| Risperidone (Risperdal) | 2nd generation (atypical) | Schizophrenia, bipolar, autism | Hyperprolactinemia, mild EPS at high doses |
2. 😔 ANTIDEPRESSANTS
Introduction
Antidepressants are medications used primarily to treat major depressive disorder (MDD), but also anxiety disorders, OCD, PTSD, panic disorder, and chronic pain syndromes. They work by increasing the availability of monoamine neurotransmitters — particularly serotonin, norepinephrine, and/or dopamine — in the synaptic cleft. The major classes include:
- SSRIs (Selective Serotonin Reuptake Inhibitors) — first-line agents; safer side effect profile
- SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors)
- TCAs (Tricyclic Antidepressants) — older, effective but more toxic
- MAOIs (Monoamine Oxidase Inhibitors) — reserved for refractory cases
- Atypicals — e.g., bupropion, mirtazapine
Full antidepressant effect typically takes 2–6 weeks to develop.
(Kaplan & Sadock's Comprehensive Textbook of Psychiatry; Katzung's Pharmacology)
5 Common Antidepressant Drugs
| Drug | Class | Key Use | Notable Side Effects |
|---|
| Fluoxetine (Prozac) | SSRI | Depression, OCD, bulimia, panic disorder | Insomnia, sexual dysfunction, GI upset |
| Sertraline (Zoloft) | SSRI | Depression, PTSD, social anxiety, OCD | Nausea, diarrhea, sexual dysfunction |
| Amitriptyline (Elavil) | TCA | Depression, neuropathic pain, migraines | Anticholinergic effects, cardiac arrhythmia, sedation |
| Venlafaxine (Effexor) | SNRI | Depression, generalized anxiety, fibromyalgia | Hypertension, nausea, discontinuation syndrome |
| Bupropion (Wellbutrin) | Atypical (NDRI) | Depression, smoking cessation | Seizure risk (dose-dependent), insomnia, no sexual dysfunction |
3. 😰 ANXIOLYTICS
Introduction
Anxiolytics are drugs used to reduce anxiety, tension, and nervousness. The most widely used class are benzodiazepines, which act by enhancing the effect of GABA (gamma-aminobutyric acid) at the GABA-A receptor, producing sedation, muscle relaxation, and anxiolysis. After their introduction in the 1960s, benzodiazepines rapidly became the most prescribed drugs in the US — about 15% of Americans have had one prescribed. However, due to risk of dependence and tolerance, their long-term use is carefully regulated (Schedule IV controlled substances). Non-benzodiazepine options (e.g., buspirone, SSRIs) are now preferred for chronic anxiety.
(Kaplan and Sadock's Synopsis of Psychiatry)
5 Common Anxiolytic Drugs
| Drug | Class | Key Use | Notable Side Effects |
|---|
| Diazepam (Valium) | Benzodiazepine | Anxiety, alcohol withdrawal, muscle spasm, seizures | Sedation, dependence, respiratory depression |
| Lorazepam (Ativan) | Benzodiazepine | Acute anxiety, status epilepticus, pre-op sedation | Sedation, amnesia, dependence |
| Alprazolam (Xanax) | Benzodiazepine | Panic disorder, generalized anxiety | High dependence potential, rebound anxiety |
| Clonazepam (Klonopin) | Benzodiazepine | Panic disorder, seizures, social anxiety | Sedation, cognitive blunting, dependence |
| Buspirone (Buspar) | Azapirone (non-BZD) | Generalized anxiety disorder (long-term) | No dependence, dizziness, delayed onset (2–4 weeks) |
4. 🔄 MOOD STABILIZERS
Introduction
Mood stabilizers are medications used to treat and prevent mood episodes in bipolar disorder (mania, hypomania, and depression). Lithium was the first and prototypical mood stabilizer, discovered to be effective for mania in 1949. A group of anticonvulsant drugs (valproate, carbamazepine, lamotrigine) has since become widely used and in many settings more common than lithium. Atypical antipsychotics (e.g., olanzapine, quetiapine) are also FDA-approved for bipolar mania. The mechanism of action of mood stabilizers is not fully understood but involves modulation of sodium channels, second messenger systems (inositol pathway), and neurotransmitter signaling.
(Katzung's Basic and Clinical Pharmacology, 16th Ed.)
5 Common Mood Stabilizer Drugs
| Drug | Class | Key Use | Notable Side Effects |
|---|
| Lithium (Eskalith) | Alkali metal salt | Bipolar mania & depression, suicide prevention | Narrow therapeutic index — tremor, polyuria, hypothyroidism, toxicity risk |
| Valproic Acid / Valproate (Depakote) | Anticonvulsant | Bipolar mania, seizures, migraine prophylaxis | Weight gain, hepatotoxicity, teratogenic (neural tube defects), thrombocytopenia |
| Carbamazepine (Tegretol) | Anticonvulsant | Bipolar mania, trigeminal neuralgia, seizures | Agranulocytosis, Stevens-Johnson syndrome, drug interactions |
| Lamotrigine (Lamictal) | Anticonvulsant | Bipolar depression (prevention of recurrence) | Serious rash (Stevens-Johnson), dizziness — slow titration required |
| Quetiapine (Seroquel) | Atypical antipsychotic | Bipolar mania & depression, schizophrenia | Sedation, weight gain, metabolic syndrome |
5. 🏃 ANTI-PARKINSONIAN DRUGS
Introduction
Anti-parkinsonian drugs are used to manage Parkinson's disease (PD) — a progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra, leading to the cardinal features of tremor, rigidity, bradykinesia, and postural instability. Treatment aims to restore dopaminergic activity in the striatum. The main approaches are:
- Dopamine precursors (levodopa) — the most effective therapy
- Dopamine agonists — stimulate dopamine receptors directly
- MAO-B inhibitors — slow dopamine breakdown
- COMT inhibitors — prolong levodopa effect
- Anticholinergics — used historically and for tremor control
Levodopa remains the gold standard but long-term use causes motor complications (wearing off, dyskinesias).
(Harrison's Principles of Internal Medicine, 22nd Ed.)
5 Common Anti-Parkinsonian Drugs
| Drug | Class | Key Use | Notable Side Effects |
|---|
| Levodopa/Carbidopa (Sinemet) | Dopamine precursor | Gold standard for PD — all motor symptoms | Dyskinesias, wearing off, nausea, orthostatic hypotension |
| Pramipexole (Mirapex) | Dopamine agonist | Early PD, restless legs syndrome | Impulse control disorders (gambling, hypersexuality), somnolence |
| Ropinirole (Requip) | Dopamine agonist | PD (early or adjunct), restless legs | Similar to pramipexole — somnolence, orthostatic hypotension |
| Selegiline (Eldepryl) | MAO-B inhibitor | Early PD, adjunct to levodopa | Insomnia, nausea; hypertensive crisis if combined with tyramine-rich foods |
| Benztropine (Cogentin) | Anticholinergic | Tremor in PD; drug-induced EPS (from antipsychotics) | Dry mouth, urinary retention, confusion (especially in elderly) |
Quick Summary Table
| Drug Class | Primary Target | Prototype Drug | Main Use |
|---|
| Antipsychotics | D₂ receptor blockade | Haloperidol / Clozapine | Schizophrenia, psychosis |
| Antidepressants | Serotonin / NE reuptake | Fluoxetine / Amitriptyline | Depression, anxiety disorders |
| Anxiolytics | GABA-A receptor | Diazepam / Buspirone | Anxiety, panic, seizures |
| Mood Stabilizers | Multiple (Na⁺ channels, etc.) | Lithium / Valproate | Bipolar disorder |
| Anti-Parkinsonian | Dopamine replenishment | Levodopa/Carbidopa | Parkinson's disease |
*Sources: Katzung's Basic and Clinical Pharmacology (16th Ed.); Kaplan & Sadock's Comprehensive Textbook of Psychiatry; Kaplan and Sadock's Synopsis of Psychiatry; Harrison's Principles of Internal Medicine (22nd Ed.)*The guide covers all 5 drug classes with a concise intro and 5 representative drugs each. Here's a quick recap of what's included:
- Antipsychotics — Typical vs. atypical, dopamine blockade; drugs: Haloperidol, Chlorpromazine, Clozapine, Olanzapine, Risperidone
- Antidepressants — SSRIs, SNRIs, TCAs, atypicals; drugs: Fluoxetine, Sertraline, Amitriptyline, Venlafaxine, Bupropion
- Anxiolytics — GABA-A enhancers (benzodiazepines); drugs: Diazepam, Lorazepam, Alprazolam, Clonazepam, Buspirone
- Mood Stabilizers — Lithium + anticonvulsants; drugs: Lithium, Valproate, Carbamazepine, Lamotrigine, Quetiapine
- Anti-Parkinsonian — Dopamine replacement strategy; drugs: Levodopa/Carbidopa, Pramipexole, Ropinirole, Selegiline, Benztropine
Each drug entry includes its drug class, key use, and notable side effects — making it practical for health teaching in a psychiatric setting.