Teach me everything about ANS pharmacology,, everything,, every drugs,every mechanisms,,every inhibitors,,every inducers,,every adverse effect,,every privileges.... From basic to scientist

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I now have extensive textbook content from Goodman & Gilman, Katzung, Lippincott, Guyton & Hall, and Barash's Clinical Anesthesia. Let me compile the complete, comprehensive guide.

🧠 AUTONOMIC NERVOUS SYSTEM (ANS) PHARMACOLOGY

The Complete Guide - Basic to Expert Level

Sources: Goodman & Gilman's Pharmacological Basis of Therapeutics | Katzung's Basic & Clinical Pharmacology 16e | Lippincott Illustrated Reviews: Pharmacology | Guyton & Hall Medical Physiology | Barash's Clinical Anesthesia 9e

PART 1: ANS ANATOMY & PHYSIOLOGY FOUNDATION

1.1 Division Overview

Division	Outflow	Preganglionic NT	Postganglionic NT	Key Receptors
Sympathetic (SNS)	Thoracolumbar (T1-L2)	ACh (nicotinic)	Norepinephrine (NE)	α1, α2, β1, β2, β3
Parasympathetic (PNS)	Craniosacral (CN III, VII, IX, X; S2-4)	ACh (nicotinic)	ACh	M1-M5 (muscarinic)
Adrenal Medulla	Preganglionic only	ACh (nicotinic)	Epinephrine (80%) + NE (20%)	Nicotinic

Both divisions use acetylcholine (ACh) at the ganglia (nicotinic receptors). The difference is the POSTGANGLIONIC transmitter.

1.2 Neurotransmitter Synthesis

Acetylcholine (ACh) Synthesis

Choline + Acetyl-CoA  →[ChAT]→  ACh

Choline is taken up by high-affinity choline transporter (CHT1) at the nerve terminal
ChAT = choline acetyltransferase (the synthetic enzyme)
ACh is stored in vesicles via VAChT (vesicular acetylcholine transporter)
Release is Ca²⁺-mediated exocytosis triggered by action potential
Degradation: Acetylcholinesterase (AChE) cleaves ACh → choline + acetate (in synaptic cleft)
Choline is recycled back into the neuron

Norepinephrine (NE) Synthesis - The Catecholamine Pathway

Tyrosine →[TH]→ DOPA →[AADC]→ Dopamine →[DβH]→ Norepinephrine →[PNMT]→ Epinephrine

TH = Tyrosine hydroxylase - RATE-LIMITING STEP
AADC = Aromatic L-amino acid decarboxylase (DOPA decarboxylase)
DβH = Dopamine β-hydroxylase (inside vesicle)
PNMT = Phenylethanolamine-N-methyltransferase (in adrenal medulla only, converts NE → Epi)
NE is stored in vesicles via VMAT2 (vesicular monoamine transporter 2)
After release, NE is removed by:
- Reuptake-1 (NET) - back into neuron (major mechanism, ~70%)
- COMT (catechol-O-methyltransferase) - in synaptic cleft/postsynaptic cell
- MAO (monoamine oxidase) - inside nerve terminal

PART 2: RECEPTORS - THE COMPLETE MAP

2.1 Cholinergic Receptors

MUSCARINIC RECEPTORS (M1-M5) - G Protein Coupled

Receptor	G Protein	Second Messenger	Location	Response
M1	Gq	↑IP₃/DAG, ↑Ca²⁺	CNS (cortex), gastric parietal cells, ganglia	Cognitive function, ↑gastric acid
M2	Gi	↓cAMP, ↑K⁺ current	Heart (SA/AV node), presynaptic terminals	↓HR, ↓AV conduction, autoreceptor inhibition
M3	Gq	↑IP₃/DAG, ↑Ca²⁺	Smooth muscle (GI, bladder, bronchi), glands, eye	Contraction, secretion, miosis, accommodation
M4	Gi	↓cAMP	CNS (striatum), presynaptic	CNS modulation
M5	Gq	↑IP₃/DAG	CNS (substantia nigra, dopaminergic neurons)	Dopamine modulation

Key mnemonic for M2/M3 in heart vs. smooth muscle: M2 = heart (EVEN number = calm down), M3 = smooth muscle/glands (ODD = active).

NICOTINIC RECEPTORS (nAChR) - Ion Channels (Ionotropic)

Subtype	Subunit Composition	Location	Clinical Relevance
NM (Muscle type)	α1₂β1δε	Neuromuscular junction	Blocked by curare, succinylcholine
NN (Neuronal type)	α3β4, α3β2	Autonomic ganglia, adrenal medulla	Blocked by hexamethonium, trimethaphan
α7 (CNS)	α7₅ (homomeric)	CNS (hippocampus), immune cells	Cognition, anti-inflammatory; target for schizophrenia drugs
α4β2 (CNS)	α4β2	Brain (most abundant neuronal type)	Nicotine addiction, smoking cessation target

All nicotinic receptors are ligand-gated Na⁺/K⁺ (and Ca²⁺) ion channels - activation causes membrane depolarization.

2.2 Adrenergic Receptors

ALPHA RECEPTORS

Receptor	G Protein	Second Messenger	Location	Response
α1	Gq	↑IP₃/DAG → ↑Ca²⁺	Vascular smooth muscle, iris (dilator), bladder neck, prostate	Vasoconstriction, mydriasis, urinary retention
α2	Gi	↓cAMP	Presynaptic terminals (autoreceptor), platelets, fat cells, CNS	↓NE release, platelet aggregation, ↓lipolysis, sedation
α2A/B/C subtypes	Gi	↓cAMP	Presynaptic, CNS, kidney	Subtype-specific effects

BETA RECEPTORS

Receptor	G Protein	Second Messenger	Location	Response
β1	Gs	↑cAMP → PKA	Heart (SA node, AV node, ventricles), kidney (JGA)	↑HR, ↑contractility, ↑renin release
β2	Gs	↑cAMP → PKA	Bronchial smooth muscle, vascular SM (skeletal muscle), uterus, liver	Bronchodilation, vasodilation, relaxation, glycogenolysis
β3	Gs	↑cAMP	Adipose tissue, bladder (detrusor)	Lipolysis, bladder relaxation

Dopamine Receptors (D1-D5) also part of catecholamine signaling:

D1/D5: Gs → ↑cAMP → vasodilation in renal/mesenteric/coronary vessels
D2/D3/D4: Gi → ↓cAMP

PART 3: CHOLINERGIC PHARMACOLOGY (PARASYMPATHOMIMETICS)

3.1 Direct-Acting Muscarinic Agonists (Choline Esters)

Drug	Cholinesterase Sensitivity	Muscarinic	Nicotinic	Duration	Clinical Use
Acetylcholine	++++ (rapid)	+++	+++	Ultra-short (<1 min)	Intraocular (miosis)
Methacholine	+ (resistant)	++++	None	Short	Bronchoprovocation testing
Carbachol	Negligible	++	+++	Longer	Glaucoma, post-op GI/bladder
Bethanechol	Negligible	++	None	30-60 min	Urinary retention, neurogenic bladder

Bethanechol is most selective for GI/bladder (no cardiac or nicotinic effects) - used for post-op urinary retention and non-obstructive urinary retention.

3.2 Direct-Acting Muscarinic Agonists (Alkaloids)

Drug	Source	Receptor	Key Use
Pilocarpine	Pilocarpus plant	M3	Glaucoma (↓IOP), Sjögren's (dry mouth/eyes), xerostomia after radiation
Muscarine	Amanita muscaria mushroom	M	Poisoning (SLUDGE) - no clinical use
Cevimeline	Synthetic	M3	Sjögren's syndrome (dry mouth)
Nicotine	Tobacco	NN, NM	Smoking cessation (NRT)
Lobeline	Lobelia	N	Investigational only

3.3 Indirect-Acting Cholinergic Agonists: REVERSIBLE AChE Inhibitors

Mechanism: Inhibit acetylcholinesterase → ↑[ACh] at all cholinergic synapses

Drug	Binding	Duration	CNS penetration	Key Uses	Key Adverse Effects
Edrophonium	Electrostatic only	Very short (5-15 min)	Poor	Diagnosis of myasthenia gravis (Tensilon test)	Bradycardia, bronchospasm
Neostigmine	Carbamylation	Medium (0.5-2h)	Poor (quaternary)	Myasthenia gravis, reverse NMJ blockade, post-op urinary retention	Cholinergic crisis, bronchospasm
Pyridostigmine	Carbamylation	Longer (3-6h)	Poor	Myasthenia gravis (drug of choice), nerve agent prophylaxis	Nausea, diarrhea, cramps
Physostigmine	Carbamylation	Medium	Good (tertiary)	Glaucoma, reverse anticholinergic toxicity, Alzheimer's (older)	CNS effects (seizures possible)
Rivastigmine	Pseudo-irreversible	~1.5h half-life	Good	Alzheimer's disease, Parkinson's dementia	GI distress (N/V/D)
Donepezil	Reversible	70h half-life	Good	Alzheimer's (mild-severe)	GI distress, insomnia
Galantamine	Reversible + allosteric	7h half-life	Good	Alzheimer's (mild-moderate)	GI distress
Tacrine	Reversible	Short	Good	Alzheimer's (OBSOLETE)	Hepatotoxicity (withdrawn)

Alzheimer's note: Donepezil is preferred for moderate-severe AD (long half-life, once daily). Combination with memantine (NMDA antagonist) improves functional outcomes in moderate-severe AD.

3.4 Irreversible AChE Inhibitors (Organophosphates)

Mechanism: Covalent phosphorylation of serine at AChE active site → permanent inactivation. New enzyme synthesis required for recovery. "Aging" = loss of alkyl group over time, making regeneration impossible.

Drug	Use	Notes
Echothiophate	Glaucoma (ophthalmic)	Long-acting, used topically
Isoflurophate (DFP)	Glaucoma (historical)	Largely obsolete
Sarin, Soman, VX, Tabun	Chemical warfare (nerve agents)	Highly toxic, CNS penetration
Parathion, Malathion	Agricultural insecticides	Parathion more toxic; malathion safer for mammals

Organophosphate Toxicity - SLUDGE/DUMBELS

SLUDGE: Salivation, Lacrimation, Urination, Defecation, GI distress, Emesis DUMBELS: Diarrhea/Diaphoresis, Urination, Miosis, Bradycardia/Bronchospasm, Emesis, Lacrimation, Salivation/Seizures

Organophosphate Poisoning Treatment

Atropine (high doses, 2-4 mg IV, repeat every 5-10 min) - blocks muscarinic effects
Pralidoxime (2-PAM) - regenerates AChE if given BEFORE aging occurs (within hours). Reactivates phosphorylated AChE by cleaving the phosphate bond. Cannot cross BBB well (poor CNS action)
Benzodiazepines - for seizures
Supportive care - airway, oxygen

PART 4: ANTICHOLINERGIC DRUGS (MUSCARINIC ANTAGONISTS)

4.1 Mechanism

Competitive antagonism at muscarinic receptors (M1-M5). Atropine blocks ALL subtypes. Block both excitatory (gut) and inhibitory (heart) muscarinic effects.

4.2 Physiological Effects of Muscarinic Blockade

System	Effect	Dose dependency
Heart	↑HR (tachycardia), ↑AV conduction	Low dose: initial bradycardia (presynaptic M1 block → ↑ACh release) then tachycardia
Eye	Mydriasis (pupil dilation), cycloplegia (loss of accommodation), ↑IOP	Medium dose
Bronchi	Bronchodilation, ↓secretions	Medium dose
GI	↓motility, ↓secretions, dry mouth (xerostomia)	Medium-high dose
Bladder	Urinary retention, ↓detrusor tone	High dose
Glands	Anhidrosis (↓sweating), dry skin	Low-medium dose
CNS	Sedation, amnesia, confusion, delirium (atropine toxic psychosis at high doses)	High dose (tertiary only)
Vascular	Cutaneous vasodilation (hot, flushed skin)	High dose

Atropine toxicity mnemonic: "Hot as a hare, dry as a bone, red as a beet, blind as a bat, mad as a hatter"

4.3 Non-selective Muscarinic Antagonists

Drug	Key Properties	Clinical Uses
Atropine	Tertiary, CNS penetrant, short-acting	Bradycardia, organophosphate antidote, pre-op (↓secretions), pupil dilation
Scopolamine	Tertiary, high CNS penetration, sedating	Motion sickness (transdermal patch), pre-op sedation, nausea
Homatropine	Tertiary, shorter than atropine	Ophthalmology (mydriasis, cycloplegia)
Ipratropium	Quaternary, NOT absorbed systemically	COPD, asthma (inhaled bronchodilator) - first-line in COPD
Tiotropium	Quaternary, once daily, M3-selective kinetics	COPD maintenance (long-acting, 24h)
Glycopyrrolate	Quaternary, no CNS penetration	Pre-op (↓secretions), peptic ulcer, with neostigmine reversal
Propantheline	Quaternary	Irritable bowel, enuresis (older use)
Hyoscine	= Scopolamine	Same uses

4.4 Selective Muscarinic Antagonists

Drug	Selectivity	Use
Pirenzepine	M1 selective	Peptic ulcer disease (↓gastric acid without major side effects)
Tripitramine	M2 selective	Research tool
Darifenacin	M3 selective	Overactive bladder (OAB) - fewer cognitive side effects
Solifenacin	M3 > M2	Overactive bladder
Tolterodine	M3 > M2 (non-selective kinetics)	Overactive bladder
Oxybutynin	M1/M3, also Na⁺ channel block	Overactive bladder, hyperhidrosis
Trospium	Quaternary, M3	Overactive bladder (no CNS, renally cleared)
Fesoterodine	Prodrug → 5-hydroxymethyl tolterodine (M3)	Overactive bladder
Aclidinium	Long-acting M3	COPD (inhaled)
Umeclidinium	Long-acting M3	COPD (inhaled, once daily)

4.5 Nicotinic Antagonists - Ganglionic Blockers

Mechanism: Block NN nicotinic receptors at autonomic ganglia (both SNS and PNS) → unpredictable, mixed effects

Drug	Mechanism	Properties	Use
Hexamethonium	Non-competitive channel block	Poorly absorbed	Research/historical; hypertensive crises (obsolete)
Trimethaphan	Competitive ganglionic block	Short-acting IV	Hypertensive emergencies, aortic dissection (historical)
Pentolinium	Non-competitive	Longer acting	Obsolete
Mecamylamine	Competitive, tertiary (CNS entry)	Oral	Hypertension (obsolete), smoking cessation research

Clinical effects of ganglionic blockade (which division predominates determines the effect):

Heart: tachycardia (PNS dominates heart) → blockade → tachycardia
Vessels: vasodilation (SNS dominates) → blockade → hypotension
GI: constipation, ↓secretions (PNS dominates) → blockade → reduced motility
Eye: mydriasis (PNS dominates) → blockade → dilated pupils
Bladder: urinary retention (PNS dominates) → blockade

4.6 Neuromuscular Junction Blockers (NM Nicotinic Antagonists)

Non-depolarizing (Competitive) Blockers - "Curariform"

Drug	Onset	Duration	Metabolism/Elimination	Notes
Tubocurarine (d-Tc)	Slow	Long	Renal, biliary	Prototype; histamine release; ganglionic block
Pancuronium	Moderate	Long	Renal (80%)	↑HR (vagolytic), ↑BP
Vecuronium	Moderate	Intermediate	Biliary (hepatic)	Minimal CV effects; pregnancy
Rocuronium	Fast (60-90 sec)	Intermediate	Hepatic/biliary	Fastest non-depolarizer; reversed by sugammadex
Atracurium	Moderate	Intermediate	Hofmann elimination (pH/temp)	Safe in renal/hepatic failure; laudanosine metabolite (seizures)
Cisatracurium	Moderate	Intermediate	Hofmann elimination	Fewer histamine release, no laudanosine issue
Mivacurium	Moderate	Short	Plasma cholinesterase	Prolonged block in pseudocholinesterase deficiency

Reversal of non-depolarizing NMB:

Neostigmine + glycopyrrolate (anticholinesterase + antimuscarinic to prevent bradycardia)
Sugammadex - modified gamma-cyclodextrin that encapsulates rocuronium/vecuronium (does NOT need anticholinesterase combination); also reverses profound blockade

Depolarizing Blockers

Drug	Mechanism	Duration	Metabolism	Notes
Succinylcholine	Persistent depolarization (Phase I block), then desensitization (Phase II)	Ultra-short (~10 min)	Plasma pseudocholinesterase	Fastest onset of all NMBs; only depolarizing agent in use

Succinylcholine adverse effects:

Hyperkalemia (dangerous in burns >24h, crush injuries, prolonged immobilization, upper motor neuron lesions - CONTRAINDICATED)
Malignant hyperthermia (with volatile anesthetics - genetic susceptibility, RYR1 mutation)
Bradycardia (especially 2nd dose in children - muscarinic stimulation)
Increased IOP, intragastric pressure
Myalgias (post-op)
Prolonged blockade in pseudocholinesterase deficiency

PART 5: ADRENERGIC PHARMACOLOGY (SYMPATHOMIMETICS)

5.1 Classification of Sympathomimetics

Direct-acting: Act directly on adrenergic receptors Indirect-acting: Cause NE release from nerve terminals (tyramine, amphetamine, ephedrine) Mixed-acting: Both (ephedrine, pseudoephedrine)

5.2 Catecholamines (Direct-Acting)

All catecholamines are metabolized rapidly by MAO and COMT → short half-life, IV use only (except epinephrine auto-injector, inhaled).

EPINEPHRINE (Adrenaline)

Receptors: α1, α2, β1, β2, β3 (all adrenergic receptors, dose-dependent)
Low dose: β2 > α → vasodilation (skeletal muscle) → ↓DBP, ↓PVR, ↑HR, ↑contractility
High dose: α1 > β → vasoconstriction → ↑SVR, ↑BP
Uses: Anaphylaxis (1st line - IM 0.5 mg 1:1000), cardiac arrest (IV 1 mg 1:10000), severe asthma, with local anesthetics (vasoconstriction → ↑duration), open-angle glaucoma
Adverse effects: Hypertension, arrhythmias, tachycardia, anxiety, headache, pulmonary edema, cerebral hemorrhage

NOREPINEPHRINE (Noradrenaline)

Receptors: α1 >> α2 > β1 (minimal β2)
Effect: Marked vasoconstriction (↑SVR, ↑DBP, ↑SBP) → reflex bradycardia (via baroreceptors)
Uses: Septic shock (vasopressor of choice per Surviving Sepsis), severe hypotension
Adverse effects: Severe hypertension, tissue necrosis (extravasation), reflex bradycardia, ischemia of extremities/kidneys

DOPAMINE

Dose-dependent receptor selectivity:
- Low ("renal") dose (1-3 mcg/kg/min): D1/D5 → renal and mesenteric vasodilation (↑GFR/renal blood flow - clinical benefit controversial)
- Medium ("cardiac") dose (3-10 mcg/kg/min): β1 → ↑HR, ↑contractility, ↑CO
- High ("vasopressor") dose (>10 mcg/kg/min): α1 → vasoconstriction (similar to NE)
Uses: Cardiogenic shock, hemodynamic support
Adverse effects: Arrhythmias, nausea, ↑IOP, tissue necrosis on extravasation

DOBUTAMINE

Receptors: β1 >>> β2 (selective beta-1 agonist; mild α1)
Effect: ↑Contractility, ↑CO, mild ↓SVR (β2); minimal ↑HR
Uses: Acute decompensated heart failure, cardiogenic shock, stress echocardiography
Adverse effects: Tachycardia, arrhythmias, ↑myocardial oxygen demand, tolerance with prolonged use

ISOPROTERENOL

Receptors: β1 = β2 (pure, non-selective beta agonist)
Effect: ↑HR, ↑contractility, ↑CO; profound vasodilation (↓SVR, ↓DBP); ↑pulse pressure
Uses: Complete heart block (temporary), refractory torsades de pointes, bradyarrhythmias (rare)
Adverse effects: Tachycardia, arrhythmias, myocardial ischemia, hypotension

5.3 Non-Catecholamine Sympathomimetics

Selective Alpha Agonists

Drug	Receptor	Use	Adverse Effects
Phenylephrine	α1 (pure)	Nasal decongestant, hypotension during spinal anesthesia, ophthalmic mydriasis, SVT (reflex vagal slowing)	Reflex bradycardia, hypertension, tissue ischemia
Oxymetazoline	α1, α2	Nasal decongestant (topical)	Rebound congestion (rhinitis medicamentosa)
Xylometazoline	α1, α2	Nasal decongestant	Same as oxymetazoline
Methoxamine	α1 (pure)	Hypotension, paroxysmal SVT	Hypertension, reflex bradycardia
Midodrine	α1 (prodrug → desglymidodrine)	Orthostatic hypotension, reflex syncope	Supine hypertension, piloerection, urinary retention
Clonidine	α2 agonist (CNS)	Hypertension, ADHD, opioid/alcohol withdrawal, pain (epidural), migraine	Sedation, dry mouth, rebound hypertension on withdrawal
α-Methyldopa	α2 agonist (central, via false transmitter α-methylNE)	Hypertension in pregnancy (drug of choice)	Sedation, positive Coombs test, hemolytic anemia, hepatotoxicity
Tizanidine	α2 agonist (spinal)	Muscle spasticity	Sedation, hepatotoxicity
Dexmedetomidine	α2 agonist (highly selective, CNS)	ICU sedation, procedural sedation	Bradycardia, hypotension, non-REM-like sedation
Brimonidine	α2 agonist (eye)	Glaucoma (↓aqueous humor production)	Local irritation, minimal systemic effects
Apraclonidine	α2 agonist (eye)	Glaucoma, post-laser IOP spike	Follicular conjunctivitis

Selective Beta-2 Agonists (SABAs and LABAs)

Drug	Duration	Route	Key Use
Albuterol (Salbutamol)	Short (4-6h)	Inhaled/IV	Acute asthma, COPD exacerbation (SABA)
Levalbuterol	Short	Inhaled	Asthma (R-enantiomer, fewer CV effects)
Terbutaline	Short-medium	SC/oral/inhaled	Asthma, tocolysis (premature labor)
Metaproterenol (Orciprenaline)	Short-medium	Inhaled/oral	Asthma (less β2-selective than albuterol)
Pirbuterol	Short	Inhaled	Asthma
Salmeterol	Long (12h)	Inhaled	Asthma maintenance (LABA - never as monotherapy), COPD
Formoterol	Long (12h)	Inhaled	Asthma maintenance, COPD (also rapid onset)
Indacaterol	Ultra-long (24h)	Inhaled	COPD (once daily)
Olodaterol	Ultra-long (24h)	Inhaled	COPD
Vilanterol	Ultra-long (24h)	Inhaled	Asthma/COPD (in combination products)
Ritodrine	Variable	IV	Tocolysis (premature labor)

β2 agonist adverse effects: Tachycardia (from β1 spillover), tremor, hypokalemia (↑cellular K⁺ uptake), hyperglycemia, lactic acidosis (high dose)

Mixed/Indirect Sympathomimetics

Drug	Mechanism	Key Effects & Uses
Amphetamine	NE/DA release from nerve terminals	CNS stimulant, ADHD, narcolepsy, appetite suppression
Methamphetamine	NE/DA release (more potent CNS)	ADHD (some uses), substance abuse
Ephedrine	Mixed (direct α/β + NE release)	Hypotension during anesthesia, nasal decongestant, asthma (older)
Pseudoephedrine	Mixed (weaker than ephedrine)	Nasal decongestant (OTC)
Tyramine	Indirect (displaces NE from vesicles)	No clinical use; dietary (cheese, wine) → hypertensive crisis in MAO inhibitor patients
Cocaine	Blocks NET (reuptake-1)	Local anesthetic (ENT), also blocks DAT → euphoria, addiction

PART 6: ADRENERGIC ANTAGONISTS (SYMPATHOLYTICS)

6.1 Alpha Blockers

Non-selective Alpha Blockers (α1 + α2)

Drug	Mechanism	Duration	Uses	Notable Properties
Phenoxybenzamine	Irreversible covalent alkylation	Very long (24-48h)	Pheochromocytoma (pre-op); phenoxybenzamine is given BEFORE beta-blockers	Non-competitive; reflex tachycardia; postural hypotension
Phentolamine	Competitive reversible	Short (15-30 min)	Pheochromocytoma (acute crisis), reversal of local anesthetic vasoconstriction	IV use; reflex tachycardia

Selective Alpha-1 Blockers

Drug	Half-life	Uses	Adverse Effects
Prazosin	3h	Hypertension, BPH, PTSD (nightmares), Raynaud's	First-dose syncope (orthostatic hypotension), dizziness, reflex tachycardia (mild)
Terazosin	12h	Hypertension, BPH	Less first-dose effect than prazosin
Doxazosin	22h	Hypertension, BPH	Least first-dose effect
Tamsulosin	14h	BPH (uroselective α1A)	Intraoperative floppy iris syndrome (IFIS) with cataract surgery
Silodosin	13h	BPH	Ejaculatory dysfunction
Alfuzosin	10h	BPH	Less CV effects than tamsulosin

Selective Alpha-2 Blockers

Drug	Mechanism	Use
Yohimbine	Competitive α2 blockade	Erectile dysfunction (historical), research tool, orthostatic hypotension
Mirtazapine	α2 presynaptic + 5HT2/3 block	Antidepressant (↑NE/5HT), sedation, appetite stimulation

6.2 Beta Blockers

General mechanism: Competitive antagonism at β1 and/or β2 receptors → ↓HR, ↓contractility, ↓renin release, ↓AV conduction, ↓CO, ↓BP

General adverse effects of ALL beta blockers:

Bradycardia, heart block
Bronchoconstriction (β2 block - worse with non-selective)
Fatigue, cold extremities
Masking of hypoglycemia (block tremor, tachycardia; sweating preserved)
Impotence
Rebound phenomenon on abrupt withdrawal (↑adrenergic sensitivity → angina, hypertension, arrhythmias)
Depression, nightmares (lipid-soluble agents: propranolol, metoprolol)
Dyslipidemia (↑TG, ↓HDL)

Beta Blocker Classification

Drug	β1 Selectivity	ISA	Lipid Solubility	Additional Properties	Key Uses
Propranolol	Non-selective	No	High	Membrane-stabilizing (quinidine-like), Na⁺ channel block	Hypertension, angina, arrhythmias, tremor, migraine prophylaxis, hyperthyroidism, performance anxiety
Nadolol	Non-selective	No	Low (renal excretion)	Long-acting	Hypertension, angina; once daily
Timolol	Non-selective	No	Moderate	-	Glaucoma (ophthalmic), hypertension, post-MI
Pindolol	Non-selective	Yes (high)	Moderate	ISA (partial agonist)	Hypertension (less bradycardia and rebound)
Oxprenolol	Non-selective	Yes	Moderate	-	Hypertension
Sotalol	Non-selective	No	Low	K⁺ channel block (Class III)	Ventricular arrhythmias, AF; prolongs QT
Labetalol	β1 = β2, also α1 block	No	Moderate	α1 blockade (3:1 to 7:1 β:α ratio)	Hypertensive urgency/emergencies, pregnancy-induced hypertension, aortic dissection
Carvedilol	β1 = β2, also α1 block	No	High	α1 blockade + antioxidant	Heart failure (all classes), hypertension, post-MI
Metoprolol	β1 selective	No	Moderate-High	-	Hypertension, angina, heart failure (succinate: MERIT-HF), MI, arrhythmias
Atenolol	β1 selective	No	Low (renal)	-	Hypertension, angina, post-MI
Bisoprolol	β1 highly selective	No	Moderate	-	Heart failure (CIBIS-II), hypertension
Betaxolol	β1 selective	No	High	-	Hypertension, glaucoma (ophthalmic)
Esmolol	β1 selective	No	Low	Very short t½ (9 min) - ester hydrolysis by RBC esterases	Supraventricular tachycardia, intraoperative hypertension, thyroid storm
Acebutolol	β1 selective	Yes (mild)	Low	Mild ISA	Hypertension, arrhythmias; less rebound
Nebivolol	β1 highly selective	No	Moderate	↑NO release via β3 and L-arginine pathway	Hypertension, heart failure; vasodilatory
Celiprolol	β1 selective, β2 partial agonist	Yes (β2)	Low	Mild bronchodilation	Hypertension (safe in mild asthma)

ISA (Intrinsic Sympathomimetic Activity) = partial agonist at receptor. Less bradycardia at rest, less bronchoconstriction, less dyslipidemia, less cold extremities. Disadvantage: Less effective for angina and post-MI cardioprotection.

Beta-blocker use in heart failure (evidence-based, only 3 approved):

Carvedilol (CAPRICORN, US Carvedilol), Metoprolol succinate (MERIT-HF), Bisoprolol (CIBIS-II)
Must be started in STABLE HF at LOW doses and titrated up

6.3 Combined Alpha + Beta Blockers

Drug	α:β Block Ratio	Route	Key Use
Labetalol	1:3 (oral), 1:7 (IV)	Oral/IV	Hypertensive emergencies, pre-eclampsia
Carvedilol	1:10	Oral	Heart failure, hypertension

PART 7: DRUGS AFFECTING CATECHOLAMINE SYNTHESIS AND STORAGE

7.1 Synthesis Inhibitors

Drug	Target Enzyme	Mechanism	Use
Metyrosine (α-methyltyrosine)	TH (tyrosine hydroxylase)	Competitive inhibitor of rate-limiting step	Pheochromocytoma (pre-op or inoperable)
Carbidopa	AADC	Peripheral DOPA decarboxylase inhibitor (doesn't cross BBB)	Parkinson's (with levodopa - ↑brain L-DOPA, ↓peripheral conversion/side effects)
Benserazide	AADC	Same as carbidopa	Parkinson's (Europe)
α-Methyldopa	AADC → forms α-methyl-NE (false transmitter, more potent α2 agonist than NE)	↓Sympathetic outflow centrally	Hypertension (especially in pregnancy)

7.2 Storage Inhibitors / Vesicular Depleters

Drug	Target	Mechanism	Use	Adverse Effects
Reserpine	VMAT1 + VMAT2	Irreversible blockade of vesicular monoamine uptake → slow depletion of NE, DA, 5-HT from ALL tissues	Hypertension (obsolete), Huntington's chorea	Depression, sedation, Parkinsonian symptoms, nasal congestion, peptic ulcer (↑PNS)
Tetrabenazine (TBZ)	VMAT2	Reversible, selective VMAT2 block → ↓DA, NE, 5-HT in CNS preferentially	Huntington's chorea (hyperkinetic movements), tardive dyskinesia	Depression, suicidal ideation, sedation, Parkinsonism
Valbenazine	VMAT2	Selective VMAT2 inhibitor (prodrug of (+)-α-HTBZ)	Tardive dyskinesia (FDA-approved 2017)	Sedation, QTc prolongation
Deutetrabenazine	VMAT2	Deuterated TBZ (longer t½, fewer peaks)	Huntington's chorea, tardive dyskinesia	Similar to TBZ but better tolerated

7.3 Release Inhibitors

Drug	Target	Mechanism	Use
Guanethidine	Adrenergic nerve terminal	Blocks NE release by displacing from vesicles + membrane stabilization; also depletes NE	Hypertension (obsolete), thyroid eye disease (eye drops)
Guanadrel	Same as guanethidine	Similar	Hypertension (obsolete)
Bretylium	Adrenergic nerve terminal	Blocks NE release	Ventricular fibrillation (historical antiarrhythmic)
Clonidine	α2 presynaptic autoreceptor	↓NE release (CNS + peripheral)	Hypertension, ADHD, opioid withdrawal
Botulinum toxin (BoTox)	Presynaptic vesicle fusion (SNARE proteins - cleaves SNAP-25, synaptobrevin)	Prevents ACh/NE exocytosis	Dystonia, blepharospasm, strabismus, cosmetic, hyperhidrosis, overactive bladder, migraine prophylaxis

PART 8: MAO AND COMT INHIBITORS

8.1 Monoamine Oxidase Inhibitors (MAOIs)

MAO metabolizes catecholamines and 5-HT in nerve terminals and gut. MAO-A > NE, 5-HT; MAO-B > DA, phenylethylamine.

Irreversible MAOIs

Drug	MAO Selectivity	Use	Key Interactions
Phenelzine	Non-selective (A+B)	Depression (treatment-resistant), atypical depression	Cheese reaction (tyramine - hypertensive crisis); sympathomimetics (→ crisis); meperidine (→ serotonin syndrome, death); SSRIs (→ serotonin syndrome)
Tranylcypromine	Non-selective (A+B)	Depression	Same dangerous interactions as phenelzine
Isocarboxazid	Non-selective (A+B)	Depression	Same
Selegiline	MAO-B selective (low dose)	Parkinson's (adjunct to L-DOPA), depression (transdermal high dose)	At higher doses loses selectivity; avoid tyramine-rich foods at doses >9mg/day

Tyramine "Cheese Effect": Tyramine normally metabolized by MAO-A in gut → harmless. On MAOIs, tyramine enters systemic circulation, enters nerve terminals, displaces NE → massive NE surge → hypertensive crisis (severe headache, HTN, stroke, death).

Reversible MAOIs (RIMAs)

Drug	Selectivity	Use	Advantage
Moclobemide	MAO-A reversible (RIMA)	Depression	Less tyramine interaction (competitive displacement); safer
Rasagiline	MAO-B irreversible	Parkinson's	More selective than selegiline; no amphetamine metabolites
Safinamide	MAO-B reversible	Parkinson's (adjunct)	Also glutamate release inhibitor

8.2 COMT Inhibitors

Catechol-O-methyltransferase (COMT) converts L-DOPA → 3-O-methylDOPA (peripherally) and DA → 3-methoxytyramine. COMT inhibitors used ONLY in Parkinson's (to enhance levodopa effect).

Drug	Type	Properties	Use	Adverse Effects
Entacapone	Peripheral COMT inhibitor	Does NOT cross BBB; given WITH each L-DOPA dose	Parkinson's (wearing off)	Diarrhea, orange discoloration of urine, dyskinesia
Tolcapone	Peripheral + Central	Crosses BBB; given TID (not with each L-DOPA dose)	Parkinson's	Hepatotoxicity (fatal cases - requires LFT monitoring); diarrhea
Opicapone	Peripheral COMT inhibitor	Once daily; potent	Parkinson's	Dyskinesia, constipation

PART 9: REUPTAKE INHIBITORS

9.1 Norepinephrine Reuptake Inhibitors (NET Blockers)

Drug	Selectivity	Use
Cocaine	NET + DAT + SERT (non-selective)	Local anesthetic (ENT), stimulant/abuse
Atomoxetine	NET selective	ADHD (non-stimulant)
Reboxetine	NET selective	Depression (Europe)
Desipramine	NET >> SERT (TCA)	Depression
Nortriptyline	NET > SERT (TCA)	Depression, neuropathic pain
Venlafaxine	SERT >> NET (SNRI)	Depression, anxiety, pain
Duloxetine	SERT + NET balanced	Depression, anxiety, neuropathic pain, fibromyalgia, SUI

9.2 Dopamine Reuptake Inhibitors (DAT Blockers)

Drug	Selectivity	Use
Cocaine	DAT + NET + SERT	Stimulant, local anesthetic
Bupropion	DAT + NET (weak)	Depression, smoking cessation (↓craving), ADHD
Methylphenidate	DAT > NET	ADHD, narcolepsy
Amphetamine	NET + DAT release + reuptake block	ADHD, narcolepsy

PART 10: EFFECTS ON SPECIFIC ORGAN SYSTEMS

10.1 Cardiovascular System

Effect	Sympathetic (via NE/Epi)	Parasympathetic (via ACh)
Heart Rate	↑ (β1 → ↑pacemaker current)	↓ (M2 → ↑IKAch, hyperpolarization)
Contractility	↑ (β1 → ↑cAMP → PKA → phospholamban)	↓ (atria)
AV conduction	↑ (β1)	↓, AV block (M2)
Ventricular automaticity	↑ (β1 → arrhythmias)	Minimal
Vascular tone	↑ (α1 - vasoconstriction) or ↓ (β2 - vasodilation)	↓ (M3 on endothelium → NO → vasodilation; mostly in special vascular beds)
Renin release	↑ (β1 in JGA)	-

10.2 Respiratory System

Drug/System	Effect
Sympathetic (β2)	Bronchodilation, ↓secretions
Parasympathetic (M3)	Bronchoconstriction, ↑secretions
β2 agonists	Bronchodilation (asthma/COPD)
Ipratropium/Tiotropium	Bronchodilation (COPD > asthma; blocks M3)

10.3 Eye

Drug/Mechanism	Effect
Muscarinic agonists (M3)	Miosis (pupil constriction), accommodation (near vision), ↓IOP
α1 agonists (phenylephrine)	Mydriasis, no cycloplegia
Anticholinergics (atropine, tropicamide)	Mydriasis + cycloplegia, ↑IOP
β blockers (timolol, betaxolol)	↓IOP (↓aqueous humor production, β2)
α2 agonists (brimonidine, apraclonidine)	↓IOP (↓aqueous humor production)
Pilocarpine	↓IOP (opens trabecular meshwork), miosis
Carbachol	↓IOP, miosis

10.4 GI Tract

Action	Drug
↑Motility/secretion	Muscarinic agonists, AChE inhibitors
↓Motility/secretion	Anticholinergics (atropine, hyoscine, glycopyrrolate)
↑Secretion via H2	Histamine; blocked by H2 antagonists (cimetidine, ranitidine)
↓Acid (M1 block)	Pirenzepine

PART 11: CLINICAL TOXIDROMES

11.1 Cholinergic Toxidrome (Organophosphate / AChE Inhibitor Poisoning)

Muscarinic (DUMBELS/SLUDGE): Diarrhea, Urination, Miosis, Bradycardia/Bronchospasm/Bronchorrhea, Emesis, Lacrimation, Salivation/Seizures Nicotinic: Muscle fasciculations, weakness, paralysis, hypertension, tachycardia (ganglionic) CNS: Anxiety, seizures, coma, respiratory depression

Treatment:

Atropine IV (titrate to dry secretions, NOT HR): 2-4 mg q5-10 min (large doses needed)
Pralidoxime (2-PAM) 1-2g IV: within first few hours before aging
Diazepam for seizures
Airway support

11.2 Anticholinergic Toxidrome

"Hot, dry, red, blind, mad" - Hyperthermia, dry skin/mouth, flushed (vasodilation), mydriasis, delirium Causes: Atropine OD, tricyclic antidepressants, antihistamines (diphenhydramine), antipsychotics, jimsonweed (Datura) Treatment: Physostigmine (tertiary AChE inhibitor - crosses BBB; 1-2 mg IV slowly), supportive care

11.3 Adrenergic Toxidrome (Sympathomimetic Toxidrome)

Features: Hypertension, tachycardia, hyperthermia, diaphoresis, mydriasis, agitation, seizures Causes: Cocaine, amphetamines, phenylephrine OD, tyramine + MAOI Treatment: Benzodiazepines first; phentolamine for severe hypertension; avoid beta-blockers alone (can worsen hypertension via unopposed alpha)

11.4 Serotonin Syndrome (vs. NMS)

Caused by excess serotonergic activity (MAOI + SSRI, MAOI + meperidine, linezolid + SSRI): Triad: Neuromuscular abnormalities (clonus, hyperreflexia), autonomic instability, altered mental status Treatment: Discontinue offending drugs; cyproheptadine (5-HT2A antagonist); benzodiazepines; cooling

PART 12: SPECIAL DRUGS AND UNIQUE MECHANISMS

12.1 Vasopressin and Vasopressin Analogs

Vasopressin (ADH): V1 receptors → vasoconstriction (via IP3/Ca²⁺, smooth muscle); V2 → water reabsorption (kidney). Used in: septic shock (0.03 units/min - vasopressor-sparing), cardiac arrest (40 units IV), bleeding esophageal varices
Terlipressin: V1 selective; hepatorenal syndrome, variceal bleeding
Desmopressin (DDAVP): V2 selective; diabetes insipidus, hemophilia A/vWD, nocturnal enuresis

12.2 Phosphodiesterase Inhibitors

These increase cAMP (and/or cGMP) by preventing its breakdown → positive inotropic and vasodilatory effects

Drug	PDE Isoform	Effect	Use
Milrinone	PDE3 (cardiac + vascular)	↑cAMP → inodilation (↑contractility + vasodilation)	Acute decompensated HF, post-cardiac surgery
Amrinone	PDE3	Same	Acute HF (obsolete/historical)
Sildenafil	PDE5 (vascular, especially pulmonary)	↑cGMP (NO pathway) → pulmonary + penile vasodilation	Erectile dysfunction, pulmonary arterial hypertension
Tadalafil	PDE5	Longer t½ (17h)	ED, PAH, BPH
Vardenafil	PDE5	Similar to sildenafil	ED
Dipyridamole	PDE3, PDE5 + adenosine uptake inhibition	Coronary vasodilation	Coronary vasodilation (stress testing), antiplatelet
Theophylline	Non-selective PDE (A1 antagonism also)	Bronchodilation, mild inotrope	COPD/asthma (narrow therapeutic index)
Caffeine	Non-selective PDE + A1/A2 antagonism	CNS stimulation, bronchodilation	Apnea of prematurity, CNS stimulant

DANGER: Sildenafil + nitrates → life-threatening hypotension (both ↑cGMP → additive vasodilation). Absolute contraindication.

12.3 Direct-Acting Vasodilators (not strictly ANS but clinically related)

Drug	Mechanism	Use
Nitroprusside	NO release → ↑cGMP in vascular SM	Hypertensive emergency (IV), controlled hypotension
Hydralazine	Direct arteriolar dilation (mechanism unclear, may involve NO)	Hypertension, heart failure (with nitrates in AAN HF)
Minoxidil	K⁺ channel opener → hyperpolarization → vasodilation	Severe refractory hypertension, male pattern baldness (topical)
Diazoxide	K⁺ channel opener	Hypertensive emergency, hypoglycemia (↓insulin)

PART 13: SUMMARY DRUG REFERENCE TABLE

13.1 Master Drug List by Category

Category	Drugs (key examples)	Receptor	Clinical Niche
Muscarinic agonists	Bethanechol, pilocarpine, methacholine, cevimeline	M1-M5	Urinary retention, glaucoma, Sjögren's, bronchoprovocation
Reversible AChE-I	Neostigmine, pyridostigmine, physostigmine, edrophonium, donepezil, rivastigmine, galantamine	↑ACh all sites	MG, NMJ reversal, Alzheimer's, anticholinergic toxicity
Irreversible AChE-I	Organophosphates (echothiophate, nerve agents, insecticides)	↑ACh all sites	Glaucoma (echothiophate), toxins
Muscarinic antagonists	Atropine, scopolamine, ipratropium, tiotropium, glycopyrrolate, oxybutynin, tolterodine, darifenacin	M1-M5	Bradycardia, COPD, OAB, pre-op, motion sickness
Ganglionic blockers	Hexamethonium, trimethaphan, mecamylamine	NN	Hypertension (historical)
NMJ blockers (non-dep)	Rocuronium, vecuronium, atracurium, pancuronium, cisatracurium	NM	Surgical paralysis, intubation
NMJ blockers (dep)	Succinylcholine	NM	Rapid sequence intubation
Non-selective sympath	Epinephrine, norepinephrine	α1, α2, β1, β2	Anaphylaxis, cardiac arrest, shock
α1 selective agonists	Phenylephrine, midodrine, methoxamine	α1	Hypotension, nasal decongestant
α2 selective agonists	Clonidine, dexmedetomidine, α-methyldopa, brimonidine	α2	HTN, sedation, glaucoma, pregnancy HTN
β1/β2 agonist	Isoproterenol	β1+β2	Heart block, refractory torsades
β2 selective agonists	Albuterol, salmeterol, formoterol, terbutaline	β2	Asthma, COPD, tocolysis
Indirect sympathomimet	Amphetamine, tyramine, ephedrine	↑NE release	ADHD, stimulants
Non-sel alpha blockers	Phenoxybenzamine, phentolamine	α1+α2	Pheochromocytoma
Sel α1 blockers	Prazosin, terazosin, doxazosin, tamsulosin	α1	HTN, BPH
β1+β2 blockers	Propranolol, nadolol, timolol, sotalol	β1+β2	HTN, angina, arrhythmias, glaucoma
β1 selective blockers	Metoprolol, atenolol, bisoprolol, esmolol, nebivolol	β1	HTN, HF, angina, arrhythmias
α+β blockers	Labetalol, carvedilol	α+β	HTN emergencies, HF
MAOIs	Phenelzine, tranylcypromine, selegiline, rasagiline	MAO-A/B	Depression, Parkinson's
COMT inhibitors	Entacapone, tolcapone, opicapone	COMT	Parkinson's (adjunct)
VMAT2 inhibitors	Reserpine, tetrabenazine, valbenazine	VMAT2	Huntington's, tardive dyskinesia
TH inhibitors	Metyrosine	TH	Pheochromocytoma

PART 14: HIGH-YIELD EXAM FACTS & CLINICAL PEARLS

Atropine low dose causes initial bradycardia - due to block of presynaptic M1 autoreceptors on vagal nerves → paradoxical ↑ACh release
Prazosin first-dose syncope - give at bedtime, start low
Phenoxybenzamine BEFORE beta-blocker in pheochromocytoma - preventing unopposed alpha-mediated vasoconstriction
Succinylcholine contraindicated after 24h in burns, crush injuries, UMN lesions, prolonged denervation (hyperkalemia risk)
Sugammadex reverses rocuronium/vecuronium regardless of depth of block (unlike neostigmine which needs partial recovery)
Sotalol is both a beta-blocker AND a class III antiarrhythmic (↑QT, risk of torsades de pointes)
Labetalol is safe in pregnancy for hypertensive emergencies
α-Methyldopa is drug of choice for hypertension in pregnancy (does not affect fetal blood flow)
Neostigmine requires anticholinergic coverage (glycopyrrolate preferred - does not cross BBB) to prevent muscarinic side effects during NMJ reversal
Tyramine + MAOI = hypertensive crisis - MAOI must be washed out 14 days before starting another serotonergic drug or dietary tyramine
Cholinesterase inhibitors for Alzheimer's only delay progression; donepezil has longest t½ (70h), tacrine withdrawn due to hepatotoxicity
Reserpine - the only antihypertensive that causes depression (depletes brain catecholamines and 5-HT)
Botulinum toxin works at cholinergic (somatic + autonomic) nerve terminals by cleaving SNARE proteins
Clonidine withdrawal syndrome - abrupt discontinuation causes severe rebound hypertension (treat with IV clonidine or labetalol)
Ipratropium preferred over atropine for COPD bronchodilation - quaternary (no systemic/CNS effects)
Physostigmine (tertiary amine) for anticholinergic toxicity because it crosses BBB; neostigmine (quaternary) does NOT cross BBB and would NOT work
Metoprolol + diltiazem/verapamil = dangerous combination - additive negative chronotropy and dromotrophy → complete heart block
Dobutamine is used for stress echocardiography due to its positive inotropic effect (↑myocardial oxygen demand unmasks ischemia)
Dexmedetomidine produces "cooperative sedation" (patient arousable) - ideal for ICU and procedural sedation
Valbenazine and deutetrabenazine - newer VMAT2 inhibitors for tardive dyskinesia with FDA approval (2017, 2017)

Sources: Goodman & Gilman's Pharmacological Basis of Therapeutics 14e | Katzung's Basic and Clinical Pharmacology 16e | Lippincott Illustrated Reviews: Pharmacology | Guyton and Hall Textbook of Medical Physiology | Barash, Cullen & Stoelting's Clinical Anesthesia 9e

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