OIA1013 SYMPATHOMIMETIC AGENTS

Sympathetic Nervous System (SNS)

Controls fight-or-flight physiological responses.

Catecholamines

Hormones like epinephrine and norepinephrine.

Non-catecholamines

Agents lacking hydroxyl groups on benzene ring.

Adrenergic Receptors

Receptors mediating sympathetic nervous system responses.

Direct-acting Agonists

Bind and activate adrenergic receptors directly.

Indirect-acting Agonists

Increase norepinephrine and epinephrine levels.

Dual-acting Agonists

Exhibit both direct and indirect actions.

Epinephrine

Primary catecholamine for emergency situations.

Norepinephrine

Key neurotransmitter in sympathetic nervous system.

Phenylephrine

Non-catecholamine used as a decongestant.

Isoproterenol

Synthetic catecholamine for bronchodilation.

Dopamine

Precursor to norepinephrine and epinephrine.

Tyrosine Hydroxylase (TH)

Converts tyrosine to dopa in synthesis pathway.

Dopa Decarboxylase

Converts dopa to dopamine in neurons.

Dopamine β-Hydroxylase

Converts dopamine to norepinephrine.

Phentolamine N-methyltransferase

Converts norepinephrine to epinephrine.

Substance P

Neurotransmitter involved in pain transmission.

Adverse Effects

Negative reactions to sympathomimetic agents.

Cardiovascular Actions

Effects on heart rate and blood pressure.

Respiratory Actions

Effects on bronchial muscle relaxation.

MAO Inhibitors

Prevent breakdown of norepinephrine.

COMT Inhibitors

Inhibit catecholamine metabolism.

Clinical Uses

Applications of sympathomimetic agents in medicine.

Adrenergic receptors

G protein coupled receptors mediating sympathetic effects.

Epinephrine

Binds α1, α2, β1; treats allergic reactions.

Norepinephrine

Precursor to epinephrine; controls blood pressure.

Dopamine

Binds dopamine receptors; affects α1, β1 receptors.

Direct-acting agonists

Bind directly to adrenergic receptors.

Isoproterenol

Synthetic agonist; primarily β receptor activity.

Dobutamine

Primarily β1 agonist; increases cardiac output.

Phenylephrine

Selective α1 agonist; causes vasoconstriction.

Clonidine

α2 agonist; reduces sympathetic outflow.

Indirect-acting agonists

Promote norepinephrine release without direct binding.

Tyramine

Releases stored norepinephrine; found in aged foods.

Amphetamine

Stimulates release of norepinephrine; increases alertness.

Cocaine

Inhibits norepinephrine reuptake; increases sympathetic effects.

Mixed acting agonists

Activate receptors via direct binding and norepinephrine release.

Ephedrine

Mixed agonist; stimulates both α and β receptors.

Mechanism of action

Agonists activate receptors, influencing second messenger systems.

Second messenger systems

IP3/DAG and cAMP mediate adrenergic receptor actions.

Adenylate cyclase

Enzyme activated by G proteins; increases cAMP.

Vasodilation

Widening of blood vessels; occurs with β receptor stimulation.

Vasoconstriction

Narrowing of blood vessels; occurs with α receptor stimulation.

G protein

Mediates signal transduction from receptor activation.

Catechol-O-methyltransferase (COMT)

Enzyme that inactivates catecholamines like norepinephrine.

Monoamine oxidase (MAO)

Enzyme that breaks down neurotransmitters including norepinephrine.

Attention deficit hyperactivity disorder (ADHD)

Low norepinephrine levels may contribute to its development.

Cleakage

Leakage of substances into tissue.

Adverse Effects

Negative reactions like anxiety and arrhythmias.

Catecholamine

A class of neurotransmitters including dopamine.

Dopamine

Precursor to norepinephrine in noradrenergic nerves.

Parkinson's Disease

Caused by lack of dopamine in the brain.

Shock Syndrome

Hemodynamic imbalance due to various medical conditions.

β-Adrenoceptors

Receptors that respond to catecholamines like dopamine.

Chronotropic Effects

Changes in heart rate due to stimulation.

Inotropic Effects

Changes in heart contractility due to stimulation.

D1 and D2 Receptors

Dopamine receptors involved in renal vasodilation.

α-Adrenergic Receptors

Receptors that increase vascular resistance when stimulated.

Isoprenaline

Non-selective beta adrenergic receptor agonist.

Heart Block

Interruption of electrical conduction in the heart.

Adams-Stokes Attacks

Transient loss of consciousness due to heart issues.

Glycogenolysis

Breakdown of glycogen to glucose in the liver.

Oxymetazoline

α1- and α2-agonist used for nasal decongestion.

Vasoconstriction

Narrowing of blood vessels to reduce blood flow.

Ephedrine

Alpha and beta-adrenergic agonist from ephedra plant.

Hypotension

Abnormally low blood pressure condition.

Renin-Angiotensin-Aldosterone System

Hormonal system regulating blood pressure and fluid balance.

Nasal Decongestant

Medication to relieve nasal congestion.

Sympathomimetic Drug

Mimics effects of the sympathetic nervous system.

Injection Site Necrosis

Tissue death at the site of injection.

Adrenergic receptors

Receptors activated by catecholamines like norepinephrine.

α-1 receptors

Cause vasoconstriction and increase blood pressure.

β-1 receptors

Increase heart rate and contractility.

β-2 receptors

Induce bronchodilation in the lungs.

Ephedrine

Stimulates α and β receptors, increases norepinephrine release.

Pseudoephedrine

A decongestant acting primarily on α receptors.

Tyramine

Monoamine that induces catecholamine release.

Blood-brain barrier (BBB)

Prevents certain substances from entering the brain.

Monoamine oxidase inhibitors (MAOIs)

Prevent breakdown of monoamines, increasing their levels.

Cheese effect

Hypertensive crisis from tyramine with MAOIs.

Tyramine-rich foods

Include cheese, chocolate, and fermented products.

Amphetamine

Promotes wakefulness, used for ADHD and narcolepsy.

Vesicular monoamine transporter (VMAT2)

Transports monoamines into vesicles in neurons.

Catechol-O-methyltransferase (COMT)

Enzyme that metabolizes catecholamines in circulation.

Cocaine

CNS stimulant, local anesthetic, and vasoconstrictor.

Norepinephrine reuptake

Process of norepinephrine being reabsorbed into neurons.

Central nervous system (CNS)

Part of the nervous system including the brain and spinal cord.

Adverse effects of cocaine

Include headaches, seizures, and cardiovascular issues.

Absorption of cocaine

60-80% absorbed via oral or nasal routes.

Indirect sympathomimetic action

Stimulates sympathetic nervous system indirectly.

MAO metabolism

Breaks down monoamines in the liver.

Hypertensive crisis

Severe increase in blood pressure due to drug interactions.

CNS disorders

Conditions affecting the brain and spinal cord.

Therapeutic uses of amphetamine

Treats ADHD and narcolepsy.

Norepinephrine (NE)

A neurotransmitter involved in arousal and alertness.