Medical Pharmacology • COMLEX & USMLE Pre-Clerkship

Foundational Pharmacology & Autonomics

Real-time pharmacokinetic and pharmacodynamic equations, autonomic second messenger cascades (HAVe 1 M&M vs MAD 2s), CYP450 metabolic modulators, and an exhaustive 20-antidote toxicology lookup vault.

Parameters

Interactive Pharmacokinetics Lab

Modify dosing variables to observe real-time recalculation of volume of distribution, clearance, half-life, and maintenance schedules.

Volume of Distribution (Vd) [L]: 50 L

Low Vd (<10L) = stays in intravascular plasma. High Vd (>45L) = lipophilic, tissue sequestration.

Clearance (CL) [L/hr]: 5.0 L/hr

Volume of plasma cleared of drug per unit time (renal + hepatic).

Target Steady-State Plasma Conc (Cp) [mg/L]: 10 mg/L

Bioavailability (F): 1.0 (100% IV)

Dosing Interval (τ) [Hours]: 8 hrs

Elimination Half-Life (t1/2)

6.9 hrs

t1/2 = (0.693 × Vd) / CL

Time to steady state (∼4-5 half-lives): 27.7 to 34.7 hrs

Loading Dose (LD)

500 mg

LD = (Cp × Vd) / F

Depends only on Volume of Distribution (Vd); unaffected by renal/hepatic impairment!

Maintenance Dose (MD)

400 mg q8h

MD = (Cp × CL × τ) / F

Depends directly on Clearance (CL); must be decreased in renal/hepatic failure!

Dosing Rate (Steady State)

50.0 mg/hr

Rate In = Rate Out = CL × Cp

At steady-state equilibrium, the rate of drug administration equals rate of drug elimination.

Zero-Order vs First-Order Elimination (Board Favorite)

Zero-Order Elimination

Constant AMOUNT eliminated per unit time

Rate is independent of plasma concentration. Metabolic enzymes become saturated. Linear decrease on linear plot. Half-life increases as concentration rises!

Mnemonic: "PEA = Phenytoin, Ethanol, Aspirin (at high toxic doses)"

First-Order Elimination

Constant FRACTION eliminated per unit time

Rate is directly proportional to plasma concentration. Constant half-life (t1/2). Exponential decay on linear plot; linear on logarithmic plot. Most drugs follow first-order.

93.75% of drug eliminated after 4 half-lives; 96.88% after 5 half-lives.

Autonomic Second Messenger Pathways

The definitive board mnemonics: HAVe 1 M&M (Gq) and MAD 2s (Gi)

Gq • HAVe 1 M&M

H1, α1, V1, M1, M3

Receptor → Gq → Phospholipase C (PLC) → ↑ IP3 + ↑ DAG → ↑ Intracellular Ca2+ → Protein Kinase C (PKC)

α1: Vascular smooth muscle constriction (mydriasis, ↑ SVR/BP, ↑ urinary sphincter tone).
M1: CNS excitation, gastric acid secretion.
M3: Bronchoconstriction, miosis (pupillary sphincter), lacrimation, salivation, sweating, bladder detrusor contraction.
H1: Bronchoconstriction, nasal mucus, pruritus, vascular permeability.
V1: Vascular smooth muscle contraction (vasopressin pressor effect).

Gi • MAD 2s

M2, α2, D2

Receptor → Gi → ↓ Adenylate Cyclase → ↓ cAMP → ↓ Protein Kinase A (PKA)

α2: Presynaptic negative feedback autoreceptor (↓ NE release, ↓ insulin release, ↓ aqueous humor production). Clonidine, α-methyldopa.
M2: Cardiac SA/AV nodal inhibition (↓ heart rate, ↓ conduction velocity, vagal tone).
D2: CNS inhibition of prolactin secretion (tuberoinfundibular pathway); extrapyramidal pathways.

Gs • All the Rest

β1, β2, β3, D1, H2, V2

Receptor → Gs → ↑ Adenylate Cyclase → ↑ cAMP → ↑ Protein Kinase A (PKA)

β1: Heart (↑ inotropy, ↑ chronotropy, ↑ dromotropy), Kidney (↑ renin release by juxtaglomerular cells).
β2: Smooth muscle relaxation: bronchodilation (Albuterol), vasodilation in skeletal muscle, uterine relaxation (tocolysis), ↑ glycogenolysis, ↑ insulin.
β3: Bladder detrusor relaxation (Mirabegron), adipose lipolysis.
H2: Gastric parietal cells (↑ H+ secretion into lumen; blocked by Famotidine).
V2: Renal collecting ducts (aquaporin-2 water reabsorption).

Organ System	Sympathetic Action & Receptor	Parasympathetic Action & Receptor	Clinical High-Yield Pearl
Pupil & Eye	Mydriasis / Dilation (pupillary dilator muscle, α1)	Miosis / Constriction (pupillary sphincter, M3); Ciliary contraction for near vision (M3)	Atropine causes severe cycloplegia (blurred near vision) and mydriasis; precipitates acute angle-closure glaucoma!
Heart	↑ HR and inotropy (β1)	↓ HR and AV conduction velocity (M2)	Carotid sinus massage stimulates CN IX afferents → ↑ vagal CN X efferents → terminates PSVT.
Bronchioles	Bronchodilation (β2)	Bronchoconstriction, ↑ secretions (M3)	Ipratropium/Tiotropium (M3 blockers) treat COPD. Non-selective β-blockers (Propranolol) can trigger fatal asthma bronchospasm.
Urinary Bladder	Internal sphincter contraction (α1), Detrusor relaxation (β3)	Detrusor contraction (M3), Internal sphincter relaxation	Bethanechol (muscarinic agonist) treats postoperative urinary retention. Oxybutynin (M3 blocker) treats urge incontinence.
Male Genitalia	Ejaculation (α1)	Erection (pelvic splanchnic nerves, NO release)	Mnemonic: "Point and Shoot" • Parasympathetic = Point (erection); Sympathetic = Shoot (ejaculation).

High-Yield Organ System Pharmacology

Cardiovascular, Renal & Antiarrhythmic Pharmacology

Nephron transport physiology, diuretic electrolyte profiles, Vaughan Williams antiarrhythmic electrophysiology, and characteristic drug-induced ECG toxicities.

Diuretics Master Class & Nephron Transport Targets

Tubular sites of action, electrolyte shifts, acid-base alterations, and high-yield board traps.

Diuretic Class & Prototype	Nephron Site & Target	Electrolyte & Acid-Base Shifts	Clinical Indications	Key Adverse Effects & Board Traps
Carbonic Anhydrase Inhibitors Acetazolamide	Proximal Convoluted Tubule (PCT) Inhibits luminal CA IV and cytoplasmic CA II	↑ Urine HCO3-, ↑ Na+, ↑ K+ Normal anion gap metabolic acidosis	Open-angle glaucoma, acute mountain (altitude) sickness, idiopathic intracranial hypertension (pseudotumor cerebri), urine alkalinization (uric acid / cystine stones).	Hyperchloremic metabolic acidosis, calcium phosphate renal stones (insoluble in alkaline urine), sulfa allergy, paresthesias.
Osmotic Diuretics Mannitol	Descending limb of Henle & PCT Non-reabsorbed sugar increases tubular osmolarity	↑ Water excretion >> ↑ Na+ Increases serum osmolarity acutely	Elevated intracranial pressure (cerebral edema), acute angle-closure glaucoma (lowers intraocular pressure).	Contraindicated in active CHF and pulmonary edema (rapid extracellular volume expansion worsens heart failure!); severe dehydration.
Loop Diuretics Furosemide, Bumetanide, Torsemide, Ethacrynic Acid	Thick Ascending Limb (TAL) Inhibits Na+/K+/2Cl- cotransporter (NKCC2); abolishes hypertonic medullary gradient	↑↑ Na+, ↑ K+, ↑ Cl-, ↑ Mg2+, ↑ Ca2+ Hypokalemic hypochloremic metabolic alkalosis	Acute pulmonary edema, acute decompensated heart failure, cirrhosis with ascites, hypercalcemia.	"Loops Lose Calcium" (hypocalcemia), Ototoxicity (dose-dependent, synergistic with aminoglycosides), sulfa allergy. Ethacrynic acid is NOT a sulfa drug (use in sulfa-allergic patients with severe edema!).
Thiazide Diuretics Hydrochlorothiazide, Chlorthalidone	Early Distal Convoluted Tubule (DCT) Inhibits Na+/Cl- cotransporter (NCCT)	↑ Na+, ↑ K+, ↑ Cl-, ↓ Ca2+ excretion Hypokalemic metabolic alkalosis, Hyponatremia	Essential hypertension (1st line), recurrent calcium nephrolithiasis (hypercalciuria), nephrogenic diabetes insipidus.	"Thiazides Save Calcium" (↑ Ca2+ reabsorption via basolateral Na+/Ca2+ exchanger). Mnemonic "hyperGLUC": HyperGlycemia, HyperLipidemia, HyperUricemia (precipitates acute gout!), HyperCalcemia. Sulfa allergy.
Aldosterone Antagonists Spironolactone, Eplerenone	Cortical Collecting Tubule (CCT) Competitively blocks intracellular mineralocorticoid receptors	↑ Na+, ↓↓ K+, ↓ H+ excretion Hyperkalemic metabolic acidosis	Heart failure with reduced ejection fraction (HFrEF - proven mortality reduction!), primary hyperaldosteronism (Conn syndrome), hepatic ascites, female hirsutism.	Hyperkalemia (peaked T waves on ECG). Spironolactone causes painful gynecomastia, decreased libido, and erectile dysfunction due to anti-androgenic effects. Eplerenone is a selective aldosterone blocker without anti-androgenic effects.
ENaC Inhibitors Amiloride, Triamterene	Cortical Collecting Tubule (CCT) Directly blocks luminal Epithelial Sodium Channels (ENaC)	↑ Na+, ↓↓ K+, ↓ H+ excretion Hyperkalemic metabolic acidosis	Liddle syndrome (gain-of-function ENaC mutation), lithium-induced nephrogenic diabetes insipidus (amiloride blocks lithium entry through ENaC).	Hyperkalemia. Does NOT cause endocrine/gynecomastia side effects.

Vaughan Williams Antiarrhythmic Electrophysiology

Myocardial and nodal action potential phase targets, QRS and QT interval impacts, and lethal drug toxicities.

Class & Prototype Drugs	Primary Channel & Mechanism	Action Potential Duration (APD) & ERP	ECG Effect (QRS / QT)	Clinical Utility & Severe Board Toxicities
Class IA Quinidine, Procainamide, Disopyramide "Double Quarter Pounder"	Moderate Na+ channel block (intermediate binding/unbinding kinetics) + some K+ block	↑ APD • ↑ Effective Refractory Period (ERP)	↑ QRS, ↑ QT interval	Atrial and ventricular arrhythmias. Torsades de pointes (due to QT prolongation). Procainamide: Drug-induced lupus erythematosus (anti-histone antibodies in slow acetylators). Quinidine: Cinchonism (headache, tinnitus, vertigo) and thrombocytopenia.
Class IB Lidocaine, Mexiletine "Lettuce, Mayo"	Weak Na+ channel block (fast unbinding kinetics). Preferentially binds ischemic / depolarized purkinje fibers.	↓ APD • ↓ ERP	No change or ↓ QT interval	Acute post-MI ventricular arrhythmias, digitalis-induced arrhythmias. Completely ineffective against supraventricular arrhythmias! Neurologic toxicity: seizures, tremor, confusion, paresthesias.
Class IC Flecainide, Propafenone "Fries, Please"	Strong Na+ channel block (slow dissociation kinetics). Marked use-dependence (stronger effect at higher heart rates).	No change in APD • ERP unchanged	↑↑ QRS duration markedly (normal QT)	Refractory atrial fibrillation, SVT in normal hearts. STRICTLY CONTRAINDICATED in structural or ischemic heart disease / post-MI (CAST trial demonstrated increased mortality from lethal ventricular proarrhythmias!).
Class II Metoprolol, Atenolol, Esmolol, Propranolol	β-adrenoceptor blockade → ↓ cAMP → ↓ Ca2+ and If pacemaker currents in SA & AV nodes	↓ SA nodal conduction • ↑ AV nodal ERP	↑ PR interval (slows AV node)	Ventricular rate control in AFib/AFlutter; SVT; post-MI mortality reduction. Adverse effects: bradycardia, AV block, bronchospasm (non-selective beta blockers in asthma), masking hypoglycemia. Esmolol has ultra-short half-life (~9 min).
Class III Amiodarone, Sotalol, Dofetilide, Ibutilide	K+ channel blockers (inhibits delayed rectifier IKr channels) → delays Phase 3 repolarization	↑↑ APD • ↑↑ ERP	↑↑ QT interval markedly	AFib, AFlutter, ventricular tachycardia. Amiodarone Quintet of Toxicities: 1) Pulmonary fibrosis, 2) Thyroid (hypo- or hyperthyroidism due to 40% iodine content), 3) Hepatotoxicity, 4) Corneal microdeposits & optic neuropathy, 5) Blue-gray photodermatitis. Remarkably low Torsades risk despite prolonged QT! Sotalol/Dofetilide have high Torsades risk.
Class IV Verapamil, Diltiazem (Non-Dihydropyridines)	L-type Ca2+ channel blockers → ↓ conduction velocity & prolonged repolarization in AV node	↓ AV nodal conduction • ↑ ERP in AV node	↑ PR interval	Rate control in AFib/AFlutter, PSVT. Contraindicated in HFrEF / systolic heart failure (negative inotropic effect worsens decompensation) and AV conduction block. Verapamil causes severe constipation and hyperprolactinemia.
Adenosine & Digoxin Miscellaneous Antiarrhythmics	Adenosine: Activates A1 receptors → Gi → ↑ K+ efflux / hyperpolarization of AV node. Digoxin: Inhibits Na+/K+ ATPase → ↑ intracellular Ca2+ (positive inotrope) + ↑ vagal parasympathetic tone (↓ AV node).	Transient AV block (Adenosine) Shortened APD • ↑ PR (Digoxin)	Transient asystole (Adenosine) Scooped ST depression (Digoxin)	Adenosine: Drug of choice for acute paroxysmal SVT conversion. Blocked by caffeine and theophylline! Causes transient flushing, chest tightness, feeling of doom. Digoxin: HFrEF + AFib. Toxicity exacerbated by hypokalemia (K+ and digoxin compete for binding site). Toxic symptoms: nausea, vomiting, yellow-green halos (xanthopsia), bidirectional VT, and hyperkalemia. Antidote: Digoxin-specific Fab fragments.

High-Yield Pharmacologic ECG Manifestations

Classic rhythm strip and lead patterns induced by QT-prolonging drugs, electrolyte modulations, and digitalis.

Lethal Ventricular Arrhythmia Lead II Continuous Strip

Torsades de Pointes (Polymorphic VT)

Sinusoidal twisting of QRS complexes around the isoelectric baseline. Preceded by prolonged QT interval (QTc > 500 ms) and an "R-on-T" PVC.

High-Yield QT-Prolonging Culprits: Class IA & Class III antiarrhythmics, Macrolides (Azithromycin), Fluoroquinolones, Antipsychotics (Haloperidol), TCAs, Methadone, Ondansetron. Triggered by hypokalemia and hypomagnesemia.

Treatment of Choice: IV Magnesium Sulfate (even if serum Mg2+ is normal!). Defibrillation if hemodynamically unstable.

Electrolyte Toxicity Precordial Leads V2-V4

Hyperkalemia (Tall, Symmetrical Peaked T Waves)

Narrow-based, tall, symmetric "tented" T waves. As potassium rises (>7.0 mEq/L): PR prolongation, loss of P waves, widening QRS → classic "sine wave" pattern and asystole/VFib.

Pharmacologic Precipitating Agents: ACE inhibitors (-prils), ARBs (-sartans), K+-sparing diuretics (Spironolactone, Amiloride), Non-selective beta blockers, Digoxin toxicity, NSAIDs, Trimethoprim (blocks ENaC).

First Step in Treatment: IV Calcium Gluconate (stabilizes cardiac myocyte membrane). Then insulin + D50, albuterol, or sodium zirconium cyclosilicate.

ST-Segment "Scooping"

Salvador Dali Mustache Sign

Cardiac Glycoside Digitalis Therapeutic vs Toxic

Digoxin Effect & Lethal Toxicity

Therapeutic Digoxin Effect: Downsloping, concave ST depression resembling "Salvador Dali's mustache", shortened QT interval, flattened/inverted T waves.

Classic Toxicity Presentation: GI upset (anorexia, nausea, vomiting), neuro (yellow-green chromatic halos / xanthopsia, confusion), arrhythmias (bidirectional VT, junctional tachycardia, accelerated AV block). Renal clearance → elderly renal insufficiency triggers toxicity.

Antidote: Digoxin-specific Fab antibody fragments (DigiFab). Normalize K+ (if hypokalemic) or treat hyperkalemia without calcium (calcium can cause stone heart!).

Medical Toxicology

25-Toxin Clinical Antidote Vault

Searchable clinical antidote registry with molecular reversal mechanisms and emergency board scenarios.

Toxin / Overdose	Specific Antidote	Reversal Mechanism	Clinical Board Vignette Clues

CNS & Psychopharmacology

Neuro & Psychiatric Pharmacology

Antidepressant mechanisms, antipsychotic extrapyramidal symptoms, antiepileptic drug toxicity matrices, and Parkinson disease therapeutics.

Antidepressants & Serotonin Syndromes

Reuptake inhibitors, receptor modulators, enzyme blockers, and hyperadrenergic toxicity distinctions.

1st-Line Agents

SSRIs & SNRIs

Fluoxetine, Sertraline, Escitalopram, Citalopram; Venlafaxine, Duloxetine.

Mechanism: SSRIs inhibit 5-HT reuptake transporter (SERT). SNRIs inhibit both SERT and NET (norepinephrine transporter). Takes 4-6 weeks for clinical response.

Adverse: Sexual dysfunction (anorgasmia, decreased libido), GI upset, SIADH (hyponatremia in elderly). Venlafaxine causes dose-dependent hypertension. Duloxetine also treats diabetic neuropathy & fibromyalgia.

Tricyclics (TCAs)

Amitriptyline & Nortriptyline

Imipramine, Clomipramine (1st-line for severe OCD), Doxepin.

Mechanism: Inhibit 5-HT and NE reuptake; also block α1, H1, mACh, and cardiac fast Na+ channels.

3 Cs of TCA Toxicity:
1. Convulsions (GABA antagonism)
2. Coma (antihistaminic / anticholinergic)
3. Cardiotoxicity (wide QRS arrhythmia & hypotension via fast Na+ channel blockade).
Antidote: IV Sodium Bicarbonate (overcomes Na+ blockade by alkaline pH & Na+ load).

MAO Inhibitors

Phenelzine, Tranylcypromine, Selegiline

MAO-A (serotonin/NE) and MAO-B (dopamine) irreversible inhibition.

Atypical Depression: Mood reactivity, leaden paralysis, interpersonal rejection sensitivity, hypersomnia.

Tyramine Reaction: Ingestion of aged cheeses, red wine, or cured meats → dietary tyramine not degraded by gut MAO-A → enters circulation and displaces stored NE → malignant hypertensive crisis. Must enforce strict 2-week washout before starting SSRIs to avoid Serotonin Syndrome!

Atypical Antidepressants

Bupropion, Mirtazapine, Trazodone

Distinct receptor targets tailored to patient comorbidities.

Bupropion (NDRI): Inhibits NE/dopamine reuptake. Zero sexual side effects, weight neutral/loss, smoking cessation. Absolute contraindication: Bulimia, anorexia nervosa, and epilepsy (significantly lowers seizure threshold!).

Mirtazapine: α2-adrenergic antagonist → ↑ NE and 5-HT release; blocks 5-HT2/3 and H1. Promotes sedation and marked appetite stimulation with weight gain (ideal for frail, underweight depressed geriatric patients!).

Trazodone: 5-HT2 and α1 blocker. Primarily used for insomnia. Adverse: Priapism ("trazo-BONE").

Antipsychotics & Extrapyramidal Symptom (EPS) Staging

First generation (typical) vs Second generation (atypical), receptor affinities, and acute vs late extrapyramidal sequelae.

Class & Specific Drugs	Receptor Binding Profile	Hallmark Adverse Effects & Clinical Pearls	Antidote / Management Strategy
1st Gen High Potency Haloperidol, Fluphenazine, Trifluoperazine	Potent D2 receptor blockade in mesolimbic pathway	Very high risk of Extrapyramidal Symptoms (EPS) and Hyperprolactinemia (galactorrhea, amenorrhea, gynecomastia). Low anticholinergic/sedative effect. EPS Chronological Timeline: • 4 hours: Acute Dystonia (painful torticollis, oculogyric crisis, trismus). • 4 days to 4 weeks: Akathisia (intense subjective motor restlessness, pacing). • 4 weeks to 4 months: Parkinsonism (cogwheel rigidity, bradykinesia, mask facies, pill-rolling tremor). • 4 months to years: Tardive Dyskinesia (involuntary choreoathetoid movements of face/tongue; often irreversible!).	Acute dystonia: IV Benztropine or Diphenhydramine (anticholinergics). Akathisia: Propranolol (Beta-blocker) or Benzodiazepine. Tardive Dyskinesia: Discontinue drug, switch to Clozapine; VMAT2 inhibitor (Valbenazine).
1st Gen Low Potency Chlorpromazine, Thioridazine	Weak D2 blockade; potent α1, H1, mACh antagonism	Low EPS risk, but prominent anticholinergic dry mouth, orthostatic hypotension (α1), and heavy sedation (H1). • Chlorpromazine: Corneal epithelial deposits ("corneal deposits = Chlorpromazine"). • Thioridazine: Retinal pigmentation ("retinal deposits = Thioridazine"), QT prolongation / Torsades risk.	Dose reduction; switch to atypical antipsychotic; monitor annual ophthalmologic exams.
2nd Gen Atypicals Clozapine, Olanzapine, Risperidone, Quetiapine, Aripiprazole, Ziprasidone	5-HT2A antagonist + D2 antagonist (Aripiprazole is partial D2 agonist)	Treats both positive and negative symptoms of schizophrenia; lower risk of EPS. • Metabolic Syndrome: Massive weight gain, dyslipidemia, diabetes (highest risk: Olanzapine & Clozapine). • Clozapine: Reserved for treatment-resistant schizophrenia and suicidality. Causes fatal Agranulocytosis (mandatory regular absolute neutrophil count [ANC] monitoring!), myocarditis, and lowers seizure threshold. • Risperidone: Highest prolactin elevation among 2nd gen. • Ziprasidone: Black box warning for QT prolongation.	Monitor fasting glucose, lipid panel, and BMI. Clozapine requires strict REMS ANC registry (>1500/µL to continue therapy).
Neuroleptic Malignant Syndrome (NMS) Idiosyncratic reaction to all antipsychotics	Acute profound central dopamine D2 receptor hypofunction	Classic Tetrad: "Lead-pipe" generalized muscle rigidity, extreme hyperthermia (>40°C), autonomic instability (tachycardia, labile BP, diaphoresis), and altered mental status. Laboratory: massive creatine kinase (CK) elevation and rhabdomyolysis with acute tubular necrosis. Distinction from Serotonin Syndrome: NMS has lead-pipe rigidity and hyporeflexia; Serotonin Syndrome has hyperreflexia, clonus, and tremor!	Immediate discontinuation of antipsychotic; ICU aggressive cooling; Dantrolene (blocks Ryanodine receptor Ca2+ release from SR) and/or Bromocriptine (dopamine agonist).

Antiepileptics, Mood Stabilizers & Parkinson Therapeutics

Channel blockers, vesicular SV2A modulators, dopamine replenishment, and dopa-decarboxylase synergy.

Broad Spectrum

Valproate, Lamotrigine, Levetiracetam

First-line for both generalized tonic-clonic and focal seizures.

Valproic Acid: Prolongs Na+ inactivation and increases GABA synthesis. Adverse: Fatal fulminant hepatotoxicity (monitor LFTs), acute pancreatitis, weight gain, alopecia, and severe neural tube defects (spina bifida) in utero!

Lamotrigine: Blocks voltage-gated Na+ channels and inhibits glutamate release. Bipolar depression. Adverse: Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) → must titrate very slowly!

Levetiracetam (Keppra): Modulates synaptic vesicle protein SV2A. Minimal drug interactions. Adverse: neuropsychiatric agitation and mood changes.

Narrow Spectrum

Phenytoin, Carbamazepine, Ethosuximide

Sodium channel blockers & absence seizure specific therapy.

Phenytoin: Blocks Na+ channels; exhibits zero-order elimination kinetics at therapeutic levels! Adverse: Gingival hyperplasia (PDGF release), hirsutism, peripheral neuropathy, megaloblastic anemia (folate), drug-induced lupus, fetal hydantoin syndrome (cleft lip/palate).

Carbamazepine: 1st line for trigeminal neuralgia & focal seizures. Potent CYP450 inducer. Adverse: Agranulocytosis / aplastic anemia, SIADH (hyponatremia), DRESS syndrome, SJS (HLA-B*1502 in Asian ancestry).

Ethosuximide: 1st line for Absence Seizures (3-Hz spike-and-wave on EEG). Blocks thalamic T-type Ca2+ channels. Mnemonic: "EFGHIJ: Ethosuximide, Fatigue, GI distress, Headache, Itching, Stevens-Johnson".

Parkinson Therapeutics

Levodopa/Carbidopa & Adjuncts

Rebalance dopamine vs acetylcholine in nigrostriatal pathway.

Levodopa / Carbidopa: L-DOPA crosses blood-brain barrier (converted to dopamine by DOPA decarboxylase). Carbidopa inhibits peripheral DOPA decarboxylase → increases CNS bioavailability from 1% to 10% and dramatically reduces peripheral side effects (nausea, arrhythmias, postural hypotension). Long-term: "on-off" motor fluctuations.

COMT Inhibitors: Entacapone (peripheral), Tolcapone (central + peripheral, hepatotoxic). Prevent peripheral degradation of L-DOPA to 3-OMD.

Dopamine Agonists: Pramipexole, Ropinirole (non-ergot, restless legs syndrome). Side effect: impulse control disorders (gambling, hypersexuality).

Amantadine: Increases dopamine release; causes livedo reticularis (purplish mottled lace rash on legs).

Anticholinergics (Benztropine, Trihexyphenidyl): M1 antagonists; improves resting tremor and rigidity.

Endocrine • Oncology • GI

Endocrine, GI & Antineoplastic Pharmacology

Diabetes insulin kinetics, oral antihyperglycemic targets, thyroid storm management, and the comprehensive Chemotherapy & Targeted Monoclonal Antibody Matrix.

Diabetes Mellitus Pharmacotherapy

Insulin PK profiles, Biguanides, SGLT2 inhibitors, GLP-1 receptor agonists, and Sulfonylureas.

Exogenous Insulins

Rapid vs Basal Kinetics

Rapid-acting (Lispro, Aspart, Glulisine): "No LAG". 15-min onset, 1-hr peak. Taken immediately before meals for postprandial glycemic spikes.

Short-acting (Regular): 30-min onset, 2-3 hr peak. IV drug of choice for Diabetic Ketoacidosis (DKA), Hyperosmolar Hyperglycemic State (HHS), and severe hyperkalemia (+ D50).

Intermediate (NPH): 1-2 hr onset, 4-10 hr peak.

Long-acting (Glargine, Detemir, Degludec): Peakless flat 24-hr basal release.

First-Line Oral Agents

Metformin & SGLT2 Inhibitors

Metformin (Biguanide): First-line type 2 DM. Inhibits mitochondrial complex I → activates AMPK → suppresses hepatic gluconeogenesis and increases peripheral insulin sensitivity. Weight neutral/loss, zero hypoglycemia risk. Adverse: GI distress, B12 deficiency, lactic acidosis (contraindicated in eGFR < 30 mL/min or before iodinated contrast!).

SGLT2 Inhibitors (-flozins: Empagliflozin, Dapagliflozin): Block Na+/glucose cotransporter 2 in proximal convoluted tubule → glucosuria. Proven mortality reduction in Heart Failure (HFrEF/HFpEF) and diabetic nephropathy! Adverse: Vulvovaginal candidiasis, UTIs, euglycemic DKA.

Incretin System

GLP-1 Agonists & DPP-4i

GLP-1 Receptor Agonists (-tides: Semaglutide, Liraglutide): Incretin mimetics → glucose-dependent insulin secretion, decreased glucagon, delayed gastric emptying, and significant central weight loss. Reduces cardiovascular events. Adverse: Nausea, gastroparesis, pancreatitis. Contraindicated in MEN2 / medullary thyroid cancer.

DPP-4 Inhibitors (-gliptins: Sitagliptin, Linagliptin): Inhibit dipeptidyl peptidase-4 → prolong endogenous GLP-1 half-life. Weight neutral, zero hypoglycemia risk.

Secretagogues & Sensitizers

Sulfonylureas & Glitazones

Sulfonylureas (Glipizide, Glyburide, Glimepiride): Close ATP-sensitive K+ channels on pancreatic β-cells → depolarization → Ca2+ influx → endogenous insulin exocytosis. High risk of hypoglycemia and weight gain (Glipizide preferred in renal insufficiency due to shorter half-life).

TZDs / Glitazones (Pioglitazone, Rosiglitazone): Bind PPAR-γ nuclear transcription factor → upregulate GLUT4 and adiponectin. Adverse: Fluid retention / peripheral edema (strictly contraindicated in Heart Failure NYHA III/IV!), bone fractures in postmenopausal women.

Antineoplastic & Targeted Monoclonal Master Matrix

Antimetabolites, DNA cross-linkers, microtubule poisons, tyrosine kinase inhibitors, and toxic rescue antidotes.

Drug Class & Agents	Molecular Mechanism & Cell Cycle Phase	Hallmark Toxicity & Adverse Profile	Specific Rescue Agent / Clinical Antidote
Methotrexate (MTX) Antimetabolite • S Phase	Competitively inhibits Dihydrofolate Reductase (DHFR) → blocks dTMP synthesis and de novo purine synthesis	Severe myelosuppression, mucositis/stomatitis, pulmonary fibrosis, and hepatotoxicity. Teratogen.	Leucovorin (Folinic Acid): bypasses DHFR to rescue non-cancerous bone marrow cells. Glucarpidase for acute renal failure.
5-Fluorouracil (5-FU) & 6-MP Pyrimidine & Purine Analogs	5-FU: Covalently complexes with folic acid to inhibit Thymidylate Synthase → dTMP starvation. 6-MP / Azathioprine: Activated by HGPRT; inhibits de novo purine synthesis.	5-FU: Myelosuppression, coronary vasospasm, hand-foot syndrome. 6-MP: Bone marrow suppression. CRITICAL DRUG INTERACTION: 6-MP is metabolized by Xanthine Oxidase → concurrent Allopurinol or Febuxostat causes lethal 6-MP accumulation!	Uridine triacetate for 5-FU overdose. Reduce 6-MP dose by 75% if patient is taking Allopurinol!
Cyclophosphamide & Ifosfamide Alkylating Agent • Cell Cycle Non-Specific	Cross-links DNA at guanine N-7 position, halting replication and transcription. Activated by hepatic CYP450.	Myelosuppression, SIADH, and Hemorrhagic Cystitis (gross hematuria, dysuria, transitional cell bladder carcinoma) caused by toxic metabolite Acrolein!	Mesna (2-mercaptoethane sulfonate) binds acrolein in urine + aggressive IV hydration.
Cisplatin & Carboplatin Platinum Compounds • Cross-linkers	Cross-link DNA intra- and interstrand strands, inducing apoptosis in solid tumors (testicular, ovarian, lung).	Severe Nephrotoxicity (acute tubular necrosis, magnesium wasting), Ototoxicity (sensorineural hearing loss / tinnitus), and peripheral neuropathy. Highly emetogenic.	Amifostine (free radical scavenger preventing nephrotoxicity) + vigorous IV saline hydration diuresis.
Doxorubicin & Bleomycin Antitumor Antibiotics	Doxorubicin: Intercalates DNA, inhibits Topoisomerase II, generates iron-dependent free radicals. Bleomycin: Binds iron and oxygen to generate free radicals → breaks DNA strands in G2 phase.	Doxorubicin: Dilated Cardiomyopathy with congestive heart failure. Bleomycin: Pulmonary Fibrosis (cough, dyspnea, bilateral basilar crackles) and hyperpigmentation (minimal myelosuppression!).	Dexrazoxane: iron-chelating agent administered to prevent Doxorubicin cardiotoxicity.
Vincristine vs Vinblastine & Taxanes Microtubule Inhibitors • M Phase	Vincristine & Vinblastine: Bind β-tubulin and inhibit microtubule polymerization (prevents mitotic spindle formation). Paclitaxel / Docetaxel: Hyperstabilize polymerized microtubules, preventing depolymerization.	• Vincristine: Peripheral Neuropathy (distal paresthesias, foot drop, paralytic ileus / severe constipation). Mnemonic: "Vincristine crisps nerves". • Vinblastine: Severe bone marrow suppression. Mnemonic: "Vinblastine blasts bone marrow". • Paclitaxel: Myelosuppression and hypersensitivity infusion reactions.	Premedicate Taxanes with corticosteroids and antihistamines. Dose adjust Vincristine for neurotoxicity.
Targeted Monoclonals & TKIs Imatinib, Trastuzumab, Rituximab, Bevacizumab	• Imatinib: Inhibits Bcr-Abl tyrosine kinase (CML t(9;22)) & c-kit (GIST). • Trastuzumab: Monoclonal antibody against HER2/neu (erbB2) receptor tyrosine kinase. • Rituximab: Monoclonal against CD20 on B-cell lymphocytes. • Bevacizumab: Monoclonal against VEGF-A (inhibits angiogenesis).	• Trastuzumab: Cardiotoxicity (decreased ejection fraction; reversible, not dose-dependent!). • Rituximab: Risk of JC virus reactivation → Progressive Multifocal Leukoencephalopathy (PML). • Bevacizumab: Severe bleeding, GI perforation, hypertension, impaired wound healing.	Echocardiogram monitoring before and during Trastuzumab. Hold Bevacizumab ≥ 4 weeks before and after major surgery.