Drugs Affecting the Sympathetic Nervous System

8/12/2019 Drugs Affecting the Sympathetic Nervous System

1/37

Drugs Affecting the

Sympathetic NervousSystem


2/37

Drugs Affecting the Sympathetic Nervous

System

NE

NE

NE

NE

NE NE

Involuntary Muscle

Membrane

Adrenergic nerve ending

Release

Metabolism Reuptake

MAO

Adrenergic Receptor


3/37


System

Alpha

Receptors

Beta 2

Receptors

Beta 1

Receptors

Adrenergic

Receptors

Beta

Receptors


4/37


System

Alpha-adrenergic Receptors

Found predominantly on smooth muscle

membrane.

When stimulated by NE or EPI produce

contraction.

Produces vasoconstriction of most blood vessels.


5/37


System

Beta-adrenergic Receptors

Found on both cardiac and some smoothmuscle membranes.

In the heart, beta 1 receptorspredominates.

When stimulated by NE or EPI, theyincrease heart rate and force ofcontraction.


6/37


System


Found on smooth muscle in the bronchus andsmooth muscles of blood vessels supplyingmuscle and the heart.

Stimulated with EPI result in relaxation.


7/37


System


In smooth muscle, beta 2 receptors

predominates.

When stimulated by EPI, they produces musclerelaxation.

Found in smooth muscles of blood vessels

supplying skeletal muscle and the coronaryarteries.

Found on smooth muscle in the bronchial tree.


8/37


System

Beta 1

Receptors

Found on smooth

muscle in the heart

Increase heart rate and

force of contraction.


9/37


System

Beta 2

Receptors

Found on smooth muscle

of blood vessels supplying

skeletal muscle and the heart.

Found on smooth

muscle in the

bronchial tree.

Vasodilatation. Bronchodilation.


10/37


System

Sympatholytic

Drugs

Sympathomimetic

Drugs

Sympathetic

Drugs


11/37


12/37


System

Alpha-adrenergic Drugs

NE prototype

Most important clinical effect is contraction of

smooth muscles.

Vasoconstriction of most blood vessels leading

to increase in blood pressure.

Contraction of sphincter muscles.


13/37


System

Contraction of

Sphincter Muscles

GI tract Urinary Tract Eyes

Inhibits movement of

intestinal contents

Restricts passage

of urine.Mydriasis


14/37


System

Alpha-adrenergic Drugs

Clinical Indications

Hypotensive states

Decongestion

Pupillary dilation


15/37


System

Adverse Effects

Hypertensive crisis

Cerebral hemorrhage

Cardiac arrhythmias

Irritation of the nasal sinuses or eye.


16/37


System

Drug Main Use

Epinephrine To increase BP

Norepinephrine To increase BP

Pseudoephedrine Nasal decongestion

Tetrahydrozoline Ophthalmic decongestion


17/37


System

Beta-adrenergic Drugs

Stimulation of the heart

Bronchodilation

Relaxes uterine smooth muscle


18/37


System

Drugs Classification Main Use

Epinephrine Alpha, Beta-1

and Beta-2

Vasopressor, Cardiac

stimulant, bronchodilator.

Isoproterenol Beta-1 and Beta-2 Cardiac stimulant,

bronchodilator.

Albuterol Beta-2 Bronchodilator.

Ritodrine Beta-2 Arrest preterm labor.


19/37


System

Epinephrine

DOC for allergic reactions

Use in combination with local anesthetics.

Used as a cardiac stimulant in emergencies.

Use in the treatment of asthma.


20/37


System

Adverse Effects

CNS stimulationtremor, restlessness,

anxiety (beta effect)

Over-stimulation of the heart (beta 1 effect)

Lower blood pressure (beta 2 effect)


21/37


System

Dopamine

Neurotransmitter in the brain.

Precursor in the synthesis of NE

Stimulates dopaminergic, beta-1 and alpha-receptors.

Use as a drug.

Dobutamine similar to dopamine but with moreBeta-1 effect.


22/37


System

NE

NE

NE

NE

Tyrosine

NEDopamineDOPA

MAO


23/37


System

DOPAMINE

DOSE

RECEPTORS

STIMULATED

EFFECTS

Low dose Stimulate dopaminergicreceptors in the renal and

mesenteric blood vessels.

Increased renal blood flow andvasodilatation.

Moderate dose Stimulates beta-1

receptors in the heart.

Increase myocardial

contractility.

Higher dose Stimulate alpha-receptors Produces vasoconstriction.


24/37


System

Alpha-adrenergic blocking drugs

Binds to Alpha receptors

Antagonizes the effects of NE and EPI

Leads to a decrease in sympathetic response

Resulting in vasodilatation and thus decrease in BP.


25/37


System

Alpha-adrenergic blocking drugs.

Clinical Indications

Treatment of hypertension.

Vasodilator in treatment of Raynauds disease.

Diagnosis of Pheochromocytoma.


26/37


System

Alpha-adrenergic blocking drugs.

Adverse Effects

Constriction of pupils

Increased GI activity

Nasal congestion

Reflex tachycardia ( if BP is lowered too much).


27/37


System

Drugs Main Use

Doxazosin Treatment of Hypertension

Prazosin Treatment of Hypertension

Phentolamine Diagnosis of pheochromocytoma.

Treatment of vascular disease.


28/37


System

Beta-adrenergic blocking drugs.

Binds to beta receptors

Antagonizes the effects of NE and EPI

Leads to a decrease in sympathetic response.

Resulting in decrease heart rate and force ofcontraction.


29/37


System

Selective Beta-1Non-selective

Beta-blocking

Drugs


30/37


System

Nonselective Blockers Main Use

Labetalol Hypertension

Nadolol Hypertension, Angina Pectoris

Pindolol Hypertension

Propanolol Hypertension, Angina Pectoris,arrhythmhias, migraine

Timolol Hypertension, post myocardial

infarction.


31/37


System

Selective Blockers Main Use

Acebutolol Hypertension, ventricular

arrhythmias.Atenolol Hypertension, Angina Pectoris

Bisoprolol Hypertension

Esmolol Supraventricular tachycardia

Metoprolol Hypertension, Angina Pectoris


32/37


System

Propranolol

Decrease heart rate

Decrease force of contraction

Decrease rate of conduction

Resulting decrease in effort and work of the heartcauses a decrease in oxygen consumption.


33/37


System

Oral and iv preparation

Drug is carried directly to the liver by the portal system.

Significant first pass metabolism.

Lipid soluble and passes into the brain.

Causes CNS sedation, depression and decreased centralsympathetic activity.


34/37


System

Used in the treatment of angina, and various

cardiac arrhythmia.

Adverse effects include nausea, vomiting and

diarrhea, bradycardia with resulting reduced

cardiac function, bronchoconstriction.

Most serious drug interactions involve therapyof beta blockers with other drugs that decrease

cardiac function (cardiac glycosides, anti-

arrhythmic drugs and calcium blockers).


35/37


System

Adrenergic neuronal blockers

Drugs that interfere with the formation

and or storage of NE

Alpha-methyl dopa

Reserpine

Guanethidine


36/37


System

NE

NE

NE

NE

TyrosineNE

DopamineDOPA

Alpha-methyl dopa

MAO

Reserpine

Guanethidine


37/37


System

Drugs Mechanism of Action Main Use

Alpha-methyl dopa Blocks formation of

Dopamine

Treatment of

hypertension

Reserpine Depletes NE storage

granule

Treatment of

hypertension

Guanethidine Block release of NE

and depletes NE

storage granule

Treatment of

hypertension

Drugs Affecting the Sympathetic Nervous System

Documents