Here is your complete deep-dive guide to all major psychiatric medication classes, based on Kaplan & Sadock:
PSYCHIATRIC MEDICATIONS - COMPLETE DEEP DIVE GUIDE
Based on Kaplan & Sadock's Synopsis and Comprehensive Textbook of Psychiatry
PART 1: ANTIPSYCHOTICS
Antipsychotics are divided into First Generation (Typical) and Second Generation (Atypical).
1A. TYPICAL (FIRST GENERATION) ANTIPSYCHOTICS (FGAs)
Mechanism of Action
"The primary mechanism of action of the typical antipsychotics/neuroleptics (e.g., chlorpromazine, haloperidol) is the antagonism of the D2 dopamine receptor." - Kaplan CTP
They block D2 receptors in all 4 dopamine pathways:
| Dopamine Pathway | Normal Function | Effect of D2 Blockade |
|---|
| Mesolimbic | Pleasure, motivation (overactive in psychosis) | ✅ THERAPEUTIC - reduces positive symptoms |
| Mesocortical | Cognition, executive function | ❌ Worsens negative symptoms, cognitive blunting |
| Nigrostriatal | Movement coordination | ❌ Extrapyramidal Side Effects (EPS) |
| Tuberoinfundibular | Inhibits prolactin | ❌ Hyperprolactinemia → galactorrhea, amenorrhea, sexual dysfunction |
Also block:
- Alpha-1 adrenergic → orthostatic hypotension, sedation
- Muscarinic (M1) → anticholinergic effects (dry mouth, urinary retention, constipation, blurred vision)
- H1 histamine → sedation, weight gain
Common FGAs
| Drug | Potency | Key Feature |
|---|
| Chlorpromazine | Low | First antipsychotic ever; most sedating; most anticholinergic |
| Haloperidol | High | Least sedating; highest EPS risk; IV available for acute agitation |
| Fluphenazine | High | Available as long-acting depot injection |
| Trifluoperazine | High | Used for anxiety as well |
| Thioridazine | Low | High anticholinergic; risk of pigmentary retinopathy; QTc prolongation |
Extrapyramidal Side Effects (EPS) - MUST KNOW
| EPS Type | Onset | Description | Treatment |
|---|
| Acute Dystonia | Hours to days | Sudden sustained muscle contraction (neck, eyes, tongue, jaw) | Benztropine IM/IV or diphenhydramine IM/IV |
| Akathisia | Days to weeks | Subjective restlessness, can't sit still - most distressing | Propranolol (first line), benzodiazepines |
| Parkinsonism | Weeks | Tremor, rigidity, bradykinesia, shuffling gait | Reduce dose, add anticholinergic (benztropine) |
| Tardive Dyskinesia (TD) | Months to years | Involuntary orofacial movements - potentially irreversible | Stop or switch drug; VMAT2 inhibitors (valbenazine, deutetrabenazine) |
Neuroleptic Malignant Syndrome (NMS) - LIFE-THREATENING
"NMS is a rare, potentially fatal consequence of neuroleptic administration. The syndrome consists of autonomic instability, hyperpyrexia, severe extrapyramidal symptoms (i.e., rigidity), and delirium." - Kaplan Synopsis
Mnemonic: FEVER
- Febrile (hyperpyrexia >38°C, can reach 41°C)
- Encephalopathy (delirium, altered consciousness)
- Vitals unstable (tachycardia, labile BP, diaphoresis)
- Elevated CK (from muscle breakdown → myoglobinuria → renal failure)
- Rigidity ("lead pipe" rigidity)
Labs: Elevated CK, leukocytosis (10,000-40,000/mm³), myoglobinuria, elevated LFTs
Treatment: Stop antipsychotic immediately, bromocriptine (dopamine agonist), dantrolene (muscle relaxant), supportive care, hydration
1B. ATYPICAL (SECOND GENERATION) ANTIPSYCHOTICS (SGAs)
Mechanism of Action
"Atypical antipsychotic agents such as clozapine and risperidone have different mechanisms of action compared to traditional neuroleptics and have an affinity for 5HT2a, alpha-adrenergic, and D4 receptors, among others." - Kaplan CTP
Key difference: Serotonin-Dopamine Antagonism (SDA)
- Block 5-HT2A (serotonin) receptors AND D2 receptors
- The 5-HT2A blockade in the nigrostriatal pathway releases dopamine → LESS EPS than FGAs
- Also less prolactin elevation (except risperidone/paliperidone)
Individual SGAs - Deep Dive
CLOZAPINE (Most important for this case!)
Class: Dibenzodiazepine - the "original" atypical antipsychotic
Receptors blocked: D1, D2, D4, 5-HT2A, 5-HT2C, alpha-1, alpha-2, H1, M1-M5 (very "dirty" drug - hits many receptors)
Unique indications:
- Treatment-resistant schizophrenia (failed ≥2 antipsychotics)
- FDA-approved to reduce suicidal behavior in schizophrenia and schizoaffective disorder - the ONLY antipsychotic with this indication
Dosing (for this patient):
- Start ½ tab (50mg) ODHS x 3 days → 1 tab (100mg) ODHS
- Usual therapeutic range: 300-450 mg/day
- Maximum: 900 mg/day
- Titrate slowly - reduces seizure and cardiovascular risk
Therapeutic drug monitoring:
- Trough level (morning, before dose)
- Minimum therapeutic threshold: 100 ng/mL
- For treatment-resistant cases: ≥350 ng/mL needed
- Seizure risk increases significantly at levels >1,200 ng/mL or doses >600 mg/day
The Famous Clozapine Side Effects:
| Side Effect | Mechanism | Notes |
|---|
| Agranulocytosis | Idiosyncratic (unknown) | 1-2% incidence; LIFE-THREATENING; requires mandatory CBC monitoring |
| Leukopenia | Direct bone marrow effect | More common; must interrupt treatment if moderate-severe |
| Seizures | Lowers seizure threshold | Dose-dependent; add valproate if seizures occur |
| Hypersalivation | M4 agonism (paradoxical) | Worst at night; treat with atropine drops, hyoscine |
| Weight gain | H1, 5-HT2C blockade | Significant - monitor BMI, glucose, lipids |
| Metabolic syndrome | Multiple mechanisms | DM, dyslipidemia, obesity |
| Myocarditis/cardiomyopathy | Unknown | Rare but fatal; monitor troponin, CRP in first month |
| Orthostatic hypotension | Alpha-1 blockade | Especially on initiation - titrate slowly |
| Sedation | H1, M1 blockade | Use to advantage (ODHS = once daily at hour of sleep) |
Mandatory CBC Monitoring Protocol:
- Baseline WBC before starting
- Weekly for first 6 months
- Biweekly for next 6 months
- Monthly thereafter (if stable)
Stop clozapine if:
- WBC < 3,000/mm³ OR
- Absolute Neutrophil Count (ANC) < 1,500/mm³
RISPERIDONE
MOA: D2 + 5-HT2A antagonist; also alpha-1, H1 blockade
Key features:
- At LOW doses (≤6 mg/day): atypical profile, minimal EPS
- At HIGH doses (>8 mg/day): behaves like a typical antipsychotic (high EPS, high prolactin)
- Highest prolactin elevation among all SGAs (more than FGAs)
- Available as: oral tablet, oral solution, IM long-acting injection (Risperdal Consta)
Dosing: 2-8 mg/day (schizophrenia); start at 1-2 mg
Side effects: Hyperprolactinemia (galactorrhea, amenorrhea, sexual dysfunction, gynecomastia), EPS at high doses, weight gain (moderate), QTc prolongation (mild)
OLANZAPINE
MOA: D1/D2/D4 + 5-HT2A + 5-HT2C + H1 + M1-M5 + alpha-1 blockade (similar to clozapine but without agranulocytosis risk)
Key features:
- One of the most effective SGAs for acute mania and schizophrenia
- Most weight gain of all SGAs (except clozapine)
- Very sedating (useful in acute agitation)
- Available as IM for acute agitation
Dosing: 5-20 mg/day
Side effects: Significant metabolic syndrome (weight gain, hyperglycemia, dyslipidemia), sedation, orthostasis
QUETIAPINE
MOA: D2 (loose binding - "hit and run"), 5-HT2A, H1, alpha-1, alpha-2 blockade; also norepinephrine reuptake inhibition (active metabolite norquetiapine)
Key features:
- Very low EPS risk (loosely binds D2)
- Commonly used for bipolar depression (approved indication)
- Active metabolite norquetiapine has antidepressant properties
- Used off-label for insomnia/anxiety at low doses (25-100 mg)
Dosing: Schizophrenia: 300-800 mg/day; Bipolar depression: 50-300 mg/day
Side effects: Sedation (most sedating SGA), weight gain, hypotension, cataracts (recommend annual eye exams), metabolic syndrome
ARIPIPRAZOLE
MOA: Partial agonist at D2 and D3 (NOT a full antagonist - acts as "dopamine stabilizer"), partial agonist at 5-HT1A, antagonist at 5-HT2A
Key features:
- "Goldilocks" of antipsychotics - stabilizes dopamine (not too much, not too little)
- Least metabolic effects of all SGAs (minimal weight gain, no glucose/lipid changes)
- Least sedating SGA
- Can cause akathisia (due to partial D2 agonism)
Dosing: 10-30 mg/day
Side effects: Akathisia (most notable), mild weight gain, nausea; low risk for metabolic syndrome
ZIPRASIDONE
MOA: D2 + 5-HT2A antagonist; also 5-HT1A partial agonist, NE/5-HT reuptake inhibition
Key features:
- Least weight gain of all SGAs
- QTc prolongation - most significant QTc effect of SGAs; avoid in patients with baseline QTc >500ms or on other QTc-prolonging drugs
- Must be taken with food (bioavailability increases 2x with food)
PALIPERIDONE (9-hydroxyrisperidone)
- Active metabolite of risperidone
- Similar profile to risperidone
- Renally excreted (safe in hepatic impairment)
- Available as once-monthly and once-3-monthly IM depot
Comparison Table: FGA vs SGA
| Feature | FGAs (e.g., Haloperidol) | SGAs (e.g., Olanzapine) |
|---|
| EPS | High | Low |
| Tardive dyskinesia | High risk | Lower risk |
| Anticholinergic effects | High (low-potency FGAs) | Low-moderate |
| Metabolic syndrome | Low | Higher (especially olanzapine, clozapine) |
| Prolactin elevation | High | Variable (risperidone = high; aripiprazole = low) |
| Negative symptoms | Less effective | Slightly better |
| Cost | Cheaper | More expensive |
PART 2: MOOD STABILIZERS
2A. LITHIUM
Drug class: Monovalent cation (salt)
Mechanism of Action
- Inhibits inositol monophosphatase → depletes inositol → alters intracellular signaling via IP3/DAG pathway
- Inhibits glycogen synthase kinase-3 (GSK-3β) → neuroprotective effects
- Modulates serotonin, dopamine, and norepinephrine neurotransmission
- Increases neurogenesis in the hippocampus
Indications
- Bipolar I Disorder - gold standard for mania (first-line)
- Bipolar maintenance (most evidence for reducing relapse)
- Augmentation in treatment-resistant depression
- Suicidality reduction (evidence for anti-suicidal effect)
Pharmacokinetics
- Absorption: Rapid and complete (oral); no protein binding
- Distribution: Distributes in total body water; crosses BBB and placenta
- Excretion: 100% renal (no hepatic metabolism)
- Half-life: ~24 hours (steady state reached in 5-7 days)
- NOT metabolized by liver - safe in hepatic disease; dose-adjust in renal disease
Dosing
- Start 300 mg TID; titrate to therapeutic level
- Usual dose: 900-2400 mg/day in divided doses
- Extended-release (Lithobid) - reduces GI side effects, once or twice daily
Therapeutic Drug Monitoring (CRITICAL)
| Level | Interpretation |
|---|
| 0.6-1.0 mEq/L | Maintenance (therapeutic range) |
| 0.8-1.2 mEq/L | Acute mania treatment |
| >1.2 mEq/L | Toxicity begins |
| >1.4 mEq/L | Toxicity common |
| >2.0 mEq/L | Severe toxicity - dialysis may be needed |
"Lithium has a narrow therapeutic index. Symptoms of toxicity include tremors, sedation, and confusion. At higher levels, delirium, seizures, and coma may occur." - Kaplan Synopsis
Draw trough level: 12 hours after last dose
Lithium Toxicity - Stages
| Level | Symptoms |
|---|
| 1.2-1.5 | Fine tremor, nausea, diarrhea, polyuria |
| 1.5-2.0 | Coarse tremor, ataxia, slurred speech, confusion |
| 2.0-2.5 | Severe tremor, fasciculations, delirium, seizures |
| >2.5 | Coma, cardiovascular collapse, death |
Memory tool for early lithium toxicity: "DARTS"
- Diarrhea
- Ataxia
- Remor (Tremor - coarse)
- Thirst (polyuria/polydipsia - NDI)
- Slurring of speech
Things that Increase Lithium Levels (→ toxicity risk)
- NSAIDs (reduce renal clearance)
- Thiazide diuretics (Na loss → lithium retention)
- ACE inhibitors / ARBs
- Dehydration, low-sodium diet, fever, vomiting
Monitoring Before and During Lithium
- Baseline: Renal function (BUN, Cr), TFTs (TSH), ECG, CBC, pregnancy test, serum calcium
- During: Lithium level every 3-6 months, Cr and TSH every 6-12 months
Side Effects
| System | Effect |
|---|
| Renal | Nephrogenic diabetes insipidus (NDI) - polyuria, polydipsia; chronic tubulointerstitial nephritis with long-term use |
| Thyroid | Hypothyroidism (up to 30% with long-term use); goiter |
| Cardiac | T-wave flattening/inversion on ECG; sinus node dysfunction |
| Neurological | Fine tremor (benign - treat with propranolol), cognitive dulling, memory complaints |
| Dermatology | Acne, psoriasis exacerbation, hair thinning |
| Teratogenicity | Ebstein's anomaly (tricuspid valve malformation) - AVOID in 1st trimester |
| GI | Nausea, diarrhea (take with food) |
| Weight | Weight gain |
2B. VALPROATE / DIVALPROEX (Valproic Acid, Sodium Valproate, Depakote)
Mechanism of Action
- Blocks voltage-gated sodium channels → membrane stabilization
- Enhances GABA activity (increases GABA synthesis, inhibits GABA breakdown)
- Inhibits T-type calcium channels
- Inhibits histone deacetylase → gene expression changes (neuroprotective)
Indications in Psychiatry
- Acute mania (as effective as lithium for mixed/dysphoric mania - possibly better)
- Bipolar maintenance
- Schizoaffective Disorder - Bipolar Type (as in our patient)
- Augmentation of antipsychotics → accelerates response in acute psychosis
- Alcohol withdrawal (CIWA-based management)
- Migraine prophylaxis
- Epilepsy (broad spectrum anticonvulsant)
Pharmacokinetics
- Protein binding: 80-95% (highly protein-bound; watch for interactions)
- Metabolism: Hepatic (glucuronidation, beta-oxidation, CYP450 minor)
- Half-life: 6-16 hours
- Active metabolite: 2-propyl-4-pentenoic acid (partially responsible for hepatotoxicity)
Dosing
- Start 250 mg BID-TID; titrate to therapeutic level
- For this patient: 500 mg x 2 tabs AM + 1 tab PM = 1500 mg/day
- Usual psychiatric dose: 750-2500 mg/day in divided doses
- Extended-release (Depakote ER) allows once-daily dosing
Therapeutic Drug Monitoring
- Therapeutic range: 50-125 mcg/mL (for psychiatry; epilepsy: 50-100 mcg/mL)
- Draw trough level (before morning dose)
Side Effects
| System | Effect | Notes |
|---|
| GI | Nausea, vomiting, diarrhea | Take with food; use extended-release form |
| Hepatotoxicity | Elevated LFTs (up to 3x normal - common); fatal hepatic necrosis (rare) | Obtain baseline LFTs; monitor regularly |
| Pancreatitis | Acute pancreatitis | Rare but potentially fatal |
| Teratogenicity | Neural tube defects (spina bifida), craniofacial defects, developmental delay | Highest teratogen risk of all mood stabilizers - AVOID in pregnancy; use contraception |
| Hematological | Leukopenia, thrombocytopenia | Monitor CBC; may need dose reduction |
| Metabolic | Hyperammonemia (even at normal levels) → confusion/encephalopathy | Check ammonia in any altered mental status on valproate |
| Neurological | Tremor, sedation, cognitive dulling | Fine tremor (treat with propranolol) |
| Weight | Significant weight gain | Common complaint |
| Hair | Hair thinning/loss (alopecia) | Can supplement with zinc/selenium |
| Endocrine | Polycystic ovary syndrome (PCOS) in women | Consider switch to lamotrigine in females |
Monitoring Before and During Valproate
- Baseline: LFTs, CBC (with platelets), pregnancy test, weight, ammonia
- During: LFTs and CBC every 6 months, drug level as needed
Drug Interactions (important!)
- Lamotrigine: Valproate inhibits lamotrigine metabolism → doubles lamotrigine levels → rash/Stevens-Johnson; must halve lamotrigine dose
- Carbamazepine: Mutual enzyme induction; complex interaction
- Aspirin: Displaces valproate from protein binding → increases free valproate
2C. CARBAMAZEPINE (Tegretol)
Mechanism of Action
- Blocks voltage-gated sodium channels (use-dependent)
- Also modulates NMDA glutamate receptors
Indications
- Bipolar disorder (especially dysphoric/mixed mania, rapid cycling)
- Trigeminal neuralgia
- Epilepsy
Key Features
- Induces its own metabolism (autoinduction) - plasma levels drop after 3-5 weeks; may need dose increase
- Induces CYP3A4 - reduces levels of many drugs including oral contraceptives, warfarin, haloperidol
Therapeutic Range: 4-12 mcg/mL
Side Effects
"Carbamazepine may produce changes in the levels of white blood cells, platelets, and, under rare circumstances, red blood cells. Anemia, aplastic anemia, leucopenia, and thrombocytopenia may all occur." - Kaplan Synopsis
| Effect | Notes |
|---|
| Aplastic anemia | Rare but life-threatening - monitor CBC |
| Agranulocytosis | Rare |
| Hyponatremia / SIADH | Usually mild; can be symptomatic |
| Teratogenicity | Spina bifida, craniofacial abnormalities, developmental delay |
| Toxicity signs | Nausea, vomiting, ataxia, nystagmus, diplopia, confusion |
| Stevens-Johnson Syndrome | Rare but severe; especially in Asian patients with HLA-B*1502 allele |
| Cardiac | Arrhythmias at high doses |
HLA-B*1502 Testing
- Mandatory before starting carbamazepine in Asian patients (Filipino, Chinese, Thai, etc.)
- This allele increases risk of Stevens-Johnson Syndrome dramatically
Monitoring: CBC, LFTs, electrolytes (sodium), drug level
2D. LAMOTRIGINE (Lamictal)
Mechanism of Action
- Blocks voltage-gated sodium channels
- Inhibits glutamate release (reduces excitatory neurotransmission)
Indications
- Bipolar depression (most effective mood stabilizer for depression component - better than lithium or valproate for depression)
- Bipolar maintenance
- Epilepsy
Key Feature: Very slow titration required
- Must titrate over 6-8 weeks
- Rapid titration = Stevens-Johnson Syndrome / Toxic Epidermal Necrolysis (TEN)
- CRITICAL INTERACTION: Valproate doubles lamotrigine levels → must use half the usual dose when combined
Typical dosing (without valproate): 25 mg/day → 50 → 100 → 200 mg over 6-8 weeks
With valproate: 25 mg every other day → 25 mg/day → 50 mg/day → 100 mg/day
Side Effects
- Stevens-Johnson Syndrome (most feared - especially with rapid titration or valproate co-administration)
- Rash (benign in most cases, but any rash requires evaluation)
- Dizziness, diplopia, ataxia
- Minimal metabolic effects - no weight gain, no cognitive dulling → preferred in women/younger patients
PART 3: ANTIDEPRESSANTS
3A. SSRIs (Selective Serotonin Reuptake Inhibitors)
Mechanism of Action
"By definition, SSRIs increase synaptic levels of serotonin by binding to the serotonin transporter." - Kaplan CTP
Block the serotonin transporter (SERT) → prevents serotonin reuptake → increases synaptic serotonin
Common SSRIs
| Drug | Dose Range | Half-life | Special Features |
|---|
| Fluoxetine (Prozac) | 20-80 mg/day | Very long (~6 days + active metabolite) | Only antidepressant safe in pregnancy (FDA Category C but most data); fewest discontinuation symptoms |
| Sertraline (Zoloft) | 50-200 mg/day | ~26 hours | Most commonly used; safe in cardiac disease; preferred in elderly |
| Escitalopram | 10-20 mg/day | ~27 hours | Most selective SSRI; fewer drug interactions; well tolerated |
| Citalopram | 20-40 mg/day | ~35 hours | QTc prolongation at doses >40 mg - max 20 mg in elderly |
| Paroxetine (Paxil) | 20-60 mg/day | Short (~21 hrs) | Most anticholinergic SSRI; most weight gain; most sexual dysfunction; worst discontinuation syndrome |
| Fluvoxamine | 50-300 mg/day | ~15 hours | Strong CYP1A2 inhibitor; used in OCD; raises clozapine levels significantly |
Indications
- Major Depressive Disorder (first-line)
- Anxiety disorders (GAD, panic disorder, social anxiety, OCD, PTSD)
- Premenstrual dysphoric disorder (PMDD)
- Bulimia nervosa
Side Effects
| Effect | Details |
|---|
| GI | Nausea, diarrhea, vomiting - most common early; take with food; usually resolves in 1-2 weeks |
| Sexual dysfunction | Decreased libido, delayed orgasm/ejaculation, anorgasmia - most common long-term complaint |
| Insomnia/agitation | Especially early in treatment; activating SSRIs (fluoxetine) worse |
| Weight gain | Variable; paroxetine worst; fluoxetine may cause initial weight loss |
| Serotonin syndrome | With other serotonergic drugs (see below) |
| SSRI discontinuation syndrome | Flu-like, dizziness, paresthesias, irritability - especially paroxetine; restart drug if needed |
| Hyponatremia | SIADH, especially in elderly |
| Bleeding risk | Platelets use serotonin; SSRIs reduce platelet aggregation - risk of GI bleed with NSAIDs |
Serotonin Syndrome (Emergency!)
Cause: Excess serotonergic activity - usually from drug combination (SSRI + MAOI, SSRI + tramadol, SSRI + linezolid, SSRI + St. John's Wort)
Triad:
- Altered mental status (agitation, confusion)
- Autonomic instability (hyperthermia, tachycardia, diaphoresis, hypertension)
- Neuromuscular abnormalities (clonus, hyperreflexia, tremor, myoclonus, incoordination)
Key differentiator from NMS: Serotonin syndrome has hyperreflexia and clonus; NMS has lead pipe rigidity (normal/decreased reflexes). Serotonin syndrome has RAPID onset (hours); NMS is gradual (days).
Treatment: Stop offending drugs, cyproheptadine (5-HT2A antagonist), benzodiazepines for agitation, supportive care
⚠️ MAOI + SSRI = ABSOLUTE CONTRAINDICATION (can cause fatal serotonin syndrome)
Washout: SSRIs 2 weeks before MAOI (fluoxetine: 5 weeks due to long half-life); MAOIs 2 weeks before SSRI
3B. SNRIs (Serotonin-Norepinephrine Reuptake Inhibitors)
MOA: Block both SERT (serotonin transporter) AND NET (norepinephrine transporter)
| Drug | Dose | Special Features |
|---|
| Venlafaxine (Effexor) | 75-375 mg/day | At low doses (<150 mg): mostly serotonergic; at high doses: both 5-HT + NE; can raise BP |
| Duloxetine (Cymbalta) | 30-120 mg/day | Approved for depression, GAD, fibromyalgia, diabetic neuropathy, chronic musculoskeletal pain |
| Desvenlafaxine | 50 mg/day | Active metabolite of venlafaxine; simpler pharmacokinetics |
Advantages over SSRIs: Better for pain syndromes (NE component), possibly more effective in severe depression
Extra side effects: Elevated BP (especially venlafaxine at high doses), more sweating, constipation (NE effect)
3C. TCAs (Tricyclic Antidepressants)
MOA
"Older generation tricyclic antidepressants (TCAs) (e.g., imipramine, doxepin) typically act as both serotonin and norepinephrine reuptake inhibitors." - Kaplan CTP
Block SERT + NET + block H1, M1, alpha-1 receptors → many side effects
Common TCAs
| Drug | Tertiary/Secondary | Special Use |
|---|
| Imipramine | Tertiary | Enuresis (bedwetting) in children |
| Amitriptyline | Tertiary | Chronic pain, migraine prophylaxis; very sedating |
| Clomipramine | Tertiary | Most potent 5-HT; OCD (most studied) |
| Nortriptyline | Secondary | Best tolerated TCA; less anticholinergic |
| Desipramine | Secondary | Most noradrenergic; least anticholinergic |
Side Effects (due to receptor blockade)
| Receptor Blocked | Effects |
|---|
| M1 (anticholinergic) | Dry mouth, urinary retention, constipation, blurred vision, tachycardia, confusion (anticholinergic delirium) |
| H1 (antihistamine) | Sedation, weight gain |
| Alpha-1 | Orthostatic hypotension, dizziness |
| Na channel blockade | Cardiac conduction delays - widened QRS, QTc prolongation, arrhythmias |
Critical Safety Issue: Cardiotoxicity
- TCAs are dangerous in overdose - narrow therapeutic index
- Lethal dose = ~10x therapeutic dose - only 1-2 week supply can be fatal
- Overdose: QRS widening → ventricular arrhythmias → seizures → death
- Avoid in suicidal patients - limit quantity dispensed
- Baseline ECG required before initiation
Monitoring: ECG, drug levels (for nortriptyline: 50-150 ng/mL)
3D. MAOIs (Monoamine Oxidase Inhibitors)
MOA
Inhibit monoamine oxidase (MAO-A and/or MAO-B) → prevents breakdown of serotonin, norepinephrine, dopamine, and tyramine
Types:
- Irreversible, non-selective: Phenelzine, Tranylcypromine, Isocarboxazid
- Reversible, selective MAO-A (RIMA): Moclobemide (fewer interactions)
- Selective MAO-B: Selegiline (Parkinson's; as antidepressant patch at high dose)
Indications
- Atypical depression (best evidence for MAOIs vs other antidepressants) - features: hypersomnia, hyperphagia, leaden paralysis, rejection sensitivity
- Treatment-resistant depression
- Panic disorder, social anxiety disorder
The Critical Interaction: Tyramine (HYPERTENSIVE CRISIS)
MAO normally breaks down dietary tyramine in the gut wall. When MAO is inhibited, tyramine from food absorbs systemically → massive norepinephrine release → hypertensive crisis
Foods to AVOID (tyramine-rich):
- Aged cheeses (the "cheese effect")
- Cured meats (salami, pepperoni)
- Fermented products (soy sauce, miso, tofu)
- Red wine, tap beer
- Overripe/spoiled foods
- Yeast extracts (Marmite)
"Treatment with MAOIs can cause orthostasis and, rarely, hypertensive crisis. Baseline blood pressure measurement should be obtained before initiation, and blood pressure should be monitored during treatment." - Kaplan Synopsis
Drug Interactions (Multiple life-threatening ones)
| Combination | Result |
|---|
| MAOI + SSRI/SNRI | Serotonin syndrome (FATAL) |
| MAOI + Meperidine (pethidine) | Hyperpyrexic coma, serotonin syndrome |
| MAOI + Sympathomimetics (decongestants, stimulants) | Hypertensive crisis |
| MAOI + TCAs | Serotonin syndrome / hypertensive crisis |
| MAOI + Tramadol | Serotonin syndrome |
Washout rule: 2 weeks between stopping MAOI and starting other serotonergic drugs (and vice versa); 5 weeks if switching FROM fluoxetine to MAOI
3E. OTHER ANTIDEPRESSANTS
| Drug | MOA | Key Feature |
|---|
| Bupropion (Wellbutrin) | NE + DA reuptake inhibitor (NDRI) | No sexual dysfunction; weight loss; used for smoking cessation; CONTRAINDICATED in eating disorders (bulimia/anorexia) and seizure disorder (lowers seizure threshold) |
| Mirtazapine (Remeron) | Alpha-2 antagonist + 5-HT2/5-HT3 antagonist (NaSSA) | Increases 5-HT and NE; very sedating; significant weight gain and appetite increase; good for depressed patients with insomnia and poor appetite; fewer sexual side effects |
| Trazodone | 5-HT2A antagonist + weak SERT inhibitor (SARI) | Low doses (50-100 mg): hypnotic/sleep aid; risk of priapism (painful sustained erection - urological emergency); alpha-1 blockade → hypotension |
| Vortioxetine | Multi-modal: SERT inhibitor + 5-HT3 antagonist + 5-HT1A agonist | Improves cognitive symptoms of depression; low sexual dysfunction |
PART 4: ANXIOLYTICS & SEDATIVE-HYPNOTICS
4A. BENZODIAZEPINES
Mechanism of Action
"Benzodiazepines potentiate the action of GABA by binding to a separate benzodiazepine site on the GABA-A receptor." - Kaplan CTP
Bind to BZ site on GABA-A receptor → increase FREQUENCY of chloride channel opening → hyperpolarization → CNS depression
(Mnemonic: Benzodiazepines = Frequency; Barbiturates = Duration of chloride channel opening)
Indications
- Acute anxiety, panic attacks
- Alcohol withdrawal (CIWA protocol - drug of choice)
- Acute agitation (IM lorazepam)
- Seizures / status epilepticus (IV diazepam, lorazepam)
- Insomnia (short-term only)
- Muscle relaxation
- Procedural sedation
Common Benzodiazepines
| Drug | Half-life | Special Features |
|---|
| Diazepam (Valium) | Long (~100 hrs with metabolites) | Status epilepticus; alcohol withdrawal; muscle relaxant |
| Lorazepam (Ativan) | Medium (~12 hrs) | No active metabolites (safe in liver disease, elderly); preferred for alcohol withdrawal (can give IM/IV); most versatile |
| Clonazepam (Klonopin) | Long (~30-40 hrs) | Panic disorder, social anxiety; less abuse potential |
| Alprazolam (Xanax) | Short-medium (~12 hrs) | Panic disorder; high abuse potential; severe discontinuation |
| Temazepam | Medium | Insomnia specifically |
| Triazolam | Very short | Insomnia (anterograde amnesia risk) |
| Midazolam | Very short | Pre-procedural sedation, ICU sedation; IV/IM |
Rule for liver disease / elderly: Use LOT - Lorazepam, Oxazepam, Temazepam → these are directly glucuronidated (no CYP450 needed, no active metabolites)
Side Effects
- CNS depression: Sedation, cognitive impairment, anterograde amnesia
- Respiratory depression: Especially combined with opioids or alcohol - potentially fatal
- Paradoxical disinhibition: Especially in elderly and children - increased agitation, aggression
- Dependence and tolerance: Both physical and psychological
- Withdrawal syndrome: Anxiety, tremor, seizures, insomnia, tachycardia - can be life-threatening (similar to alcohol withdrawal)
Benzodiazepine Overdose
- Treatment: Flumazenil (competitive antagonist at BZ receptor)
- Caution: Flumazenil can precipitate withdrawal seizures in dependent patients; short-acting (may need repeat dosing)
4B. BUSPIRONE (Buspar)
MOA
- 5-HT1A partial agonist (serotonin)
- Some D2 partial agonism
Key Features
- For Generalized Anxiety Disorder (GAD) - first-line non-benzodiazepine option
- No dependence, no tolerance, no withdrawal
- No abuse potential
- Takes 2-4 weeks to work (like an antidepressant - not acute)
- Does NOT work for acute anxiety/panic attacks
- Does NOT cross-tolerate with benzodiazepines (cannot substitute during benzo withdrawal)
- Minimal sedation, no cognitive impairment
Dosing: 15-30 mg/day in divided doses
4C. Z-DRUGS (Non-benzodiazepine hypnotics)
| Drug | MOA | Features |
|---|
| Zolpidem (Ambien) | GABA-A BZ receptor agonist (selective omega-1) | Most prescribed sleep aid; next-day sedation; complex sleep behaviors (sleepwalking, sleep-eating); amnesia |
| Zaleplon | Similar; ultra-short half-life | Can be taken in middle of night if ≥4 hrs sleep remaining |
| Eszopiclone (Lunesta) | Similar; longer half-life | Metallic taste; approved for long-term use |
All Z-drugs can cause dependence; use with caution in elderly (fall risk)
4D. HYDROXYZINE
- H1 antihistamine with anxiolytic properties
- Non-habit-forming; no dependence
- Used for acute anxiety, pruritus, nausea
- Can be used in patients with substance use disorder (safe)
- Side effects: sedation, anticholinergic effects
QUICK SUMMARY TABLE - "The Big Picture"
| Class | First-Line Use | Key MOA | #1 Danger |
|---|
| Typical Antipsychotics | Acute psychosis (low cost) | D2 blockade | NMS, Tardive Dyskinesia |
| Atypical Antipsychotics | Schizophrenia, Bipolar, SzAD | D2 + 5-HT2A blockade | Metabolic syndrome (clozapine: agranulocytosis) |
| Lithium | Bipolar I mania, maintenance | Inositol phosphatase inhibition | Narrow therapeutic index, toxicity |
| Valproate | Bipolar, mixed mania, SzAD | Na channel block, ↑GABA | Hepatotoxicity, teratogenicity |
| Carbamazepine | Bipolar, dysphoric mania | Na channel block | Aplastic anemia, SJS (HLA-B*1502) |
| Lamotrigine | Bipolar depression | Na channel block, ↓Glu | SJS (rapid titration), doubled by valproate |
| SSRIs | MDD, Anxiety (first-line) | SERT blockade | Serotonin syndrome with MAOIs |
| SNRIs | MDD, Pain syndromes | SERT + NET blockade | Hypertension (venlafaxine) |
| TCAs | Refractory MDD, OCD, pain | SERT + NET + multiple receptors | Cardiotoxicity in overdose |
| MAOIs | Atypical/refractory depression | MAO inhibition | Hypertensive crisis (tyramine), Serotonin syndrome |
| Benzodiazepines | Acute anxiety, alcohol withdrawal | GABA-A ↑Cl⁻ frequency | Dependence, respiratory depression |
| Buspirone | GAD (non-addictive) | 5-HT1A partial agonist | Slow onset (not for acute use) |
Sources: Kaplan & Sadock's Synopsis of Psychiatry (9781975145569); Kaplan & Sadock's Comprehensive Textbook of Psychiatry (9781975175733)