Adrenergic agonists

Direct acting selective α1 agonist

Phenylephrine

Direct acting selective α2 agonist

Clonidine

Direct acting selective β1 agonist

Dobutamine

Direct acting selective β2 agonist

Salbutamol

Direct acting non‑selective α1α2β1β2 agonist

Adrenaline

Direct acting non‑selective α1α2β1 agonist

Noradrenaline

Direct acting non‑selective β1β2 agonist

Isoprenaline

Direct acting dose‑dependent agonist (D1 β1 α1)

Dopamine

Indirect acting releasing agent

Amphetamine

Indirect acting uptake inhibitor

Amitriptyline

Indirect acting enzyme inhibitor (MAO/COMT)

Selegiline, Entacapone

Mixed acting sympathomimetic

Ephedrine

Neurotransmitter at all preganglionic sites

Acetylcholine

Neurotransmitter at parasympathetic postganglionic endings

Acetylcholine

Neurotransmitter at sympathetic sweat glands

Acetylcholine

Neurotransmitter at skeletal muscle NMJ

Acetylcholine

Neurotransmitter at most sympathetic postganglionic endings

Norepinephrine

Neurotransmitter secreted by adrenal medulla

Norepinephrine + Epinephrine

Neurotransmitter at renal vasculature

Dopamine

α1 receptor location

Vascular smooth muscle, bladder trigone/sphincter, radial iris muscle

α1 receptor action

Vasoconstriction, contraction, mydriasis

α2 receptor location

Presynaptic terminals, pancreas

α2 receptor action

Inhibition of transmitter release, inhibition of insulin release

β1 receptor location

Heart, kidney

β1 receptor action

Myocardial stimulation, renin secretion

β2 receptor location

Respiratory, uterine, vascular smooth muscle, pancreas, liver, muscle spindles

β2 receptor action

Bronchodilation, uterine relaxation, vasodilation, tremors, increased glucose output

β3 receptor location

Adipose tissue

β3 receptor action

Lipolysis

D1 receptor location

Renal vascular smooth muscle

D1 receptor action

Vasodilation, increased renal perfusion

D2 receptor location

Nerve endings in CNS and GIT

D2 receptor action

Modulation of transmitter release, CNS stimulation

Adrenaline low dose effect

β2 mediated vasodilation → fall in BP

Adrenaline high dose effect

α1 mediated vasoconstriction → rise in BP

Adrenaline cardiac effects

Positive ionotropic, chronotropic, dromotropic, bathmotropic → ↑ CO and systolic BP

Adrenaline vascular effects

Cutaneous vasoconstriction (α1), skeletal muscle vasodilation (β2)

Adrenaline respiratory effect

Bronchodilation (β2)

Adrenaline clinical uses

Cardiac arrest, anaphylaxis, severe asthma, prolongation of local anesthetics

Noradrenaline receptor profile

α1, α2, β1 agonist, no β2 action

Noradrenaline CVS effects

↑ systolic and diastolic BP via vasoconstriction, reflex bradycardia

Noradrenaline clinical uses

Septic shock, hypotension

Drug abolishing NA‑induced bradycardia

Atropine

Dopamine low dose effect

D1 stimulation → ↑ renal blood flow

Dopamine moderate dose effect

β1 stimulation → ↑ cardiac output

Dopamine high dose effect

α1 stimulation → vasoconstriction

Dopamine clinical uses

Cardiogenic shock, CHF with oliguria, renal insufficiency with circulatory failure

Isoprenaline receptor profile

β1 and β2 agonist

Isoprenaline CVS effects

↑ HR and contractility (β1), ↓ TPR and diastolic BP (β2)

Isoprenaline clinical uses

Bradycardia, AV block

Phenylephrine receptor profile

Selective α1 agonist

Phenylephrine effects

Arterial vasoconstriction, ↑ BP, mucosal decongestion, mydriasis

Phenylephrine clinical uses

Nasal decongestant, mydriatic agent, hypotension

Clonidine receptor profile

Selective central α2 agonist

Clonidine effects

↓ sympathetic outflow, ↓ BP, bradycardia

Clonidine clinical uses

Hypertension

Clonidine adverse effect

Rebound hypertension on withdrawal

Dobutamine receptor profile

Selective β1 agonist

Dobutamine effects

↑ HR, contractility, conduction, excitability

Dobutamine clinical uses

Acute CHF, cardiogenic shock

Salbutamol receptor profile

Selective β2 agonist

Salbutamol effects

Bronchodilation, vasodilation, uterine relaxation

Salbutamol clinical uses

Asthma, preterm labour

Salbutamol adverse effects

Tachycardia, palpitations, tremors

Amphetamine mechanism

Stimulates release of NA, dopamine, adrenaline from nerve terminals

Amphetamine effects

CNS stimulation, euphoria, excitation, ↑ BP, myocardial stimulation

Amphetamine clinical uses

ADHD, appetite suppressant, drug of abuse

Amitriptyline mechanism

Blocks NA reuptake → ↑ synaptic NA

Amitriptyline effects

Improves mood, tachycardia, arrhythmias

Amitriptyline clinical uses

Depression

MAO enzyme function

Metabolises catecholamines intracellularly, isoforms A (NA, Adr, serotonin) and B (dopamine)

COMT enzyme function

Metabolises catecholamines extracellularly in CNS and peripheral tissues

Selegiline mechanism

MAO‑B inhibitor → ↑ dopamine

Selegiline clinical use

Parkinson’s disease

MAO‑A inhibitors clinical use

Depression

MAO inhibitor adverse effect

Cheese reaction (hypertensive crisis with tyramine foods)

Ephedrine mechanism

Non‑selective α1, α2, β1, β2 agonist + ↑ NA release

Ephedrine effects

↑ TPR, ↑ HR, bronchodilation, CNS stimulation

Ephedrine clinical uses

Asthma (historical), nasal decongestant, drug of abuse

Adrenaline vs Noradrenaline in asthma

Adrenaline effective via β2 bronchodilation, Noradrenaline ineffective (no β2 action)

Pretreatment with β blockers effect

Blocks β2 bronchodilation → reduces adrenaline benefit in asthma

Pretreatment with α1 blockers effect

Blocks vasoconstriction → adrenaline causes only β2 vasodilation → ↓ BP

Adrenaline preferred in anaphylaxis

Provides bronchodilation + vasoconstriction, Noradrenaline lacks bronchodilation

Dopamine vs Noradrenaline in cardiogenic shock

Dopamine improves renal perfusion (D1) + ↑ CO (β1), Noradrenaline worsens renal perfusion (α1 vasoconstriction)

Catecholamine not endogenous

Isoprenaline

Catecholamine causing bradycardia

Noradrenaline (via reflex)

Catecholamine with biphasic BP effect

Adrenaline (↓ BP at low dose, ↑ BP at high dose)

Catecholamine useful in asthma

Adrenaline (β2 bronchodilation)

Catecholamine improving renal blood flow at low dose

Dopamine

Adrenaline cardiac effects except

Does not increase refractory period

False statement

NA increases HR (actually reflex bradycardia)

Pressor agent under halothane anesthesia not stimulating β1

Phenylephrine

Best sympathomimetic for renal perfusion in septic shock

Dopamine

Drug class causing cheese reaction

MAO inhibitors

Drug for pupillary dilation without cycloplegia

Phenylephrine

Drug least affecting HR in cardiac transplant patient

Phenylephrine

Drug X effects (↑ systolic BP, ↓ diastolic BP, ↑ HR)

β1, β2 agonist profile

Drug A trial profile (↑ systolic/diastolic BP, ↓ HR)

Noradrenaline

Drug B trial profile (↑ systolic BP, ↓ diastolic BP, ↑ HR)

Adrenaline

Drug C trial profile (↑ systolic BP, ↓ diastolic BP, ↑ HR strongly)

Isoprenaline