Drugs Acting on the Autonomic Nervous System

8/11/2019 Drugs Acting on the Autonomic Nervous System

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Drugs Acting on the

Autonomic NervousSystemMs. Cres P. QuinzonSalalah Nursing Institute

1stSemester 2014-2015


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Objectives

By the end of this session, the students will be

able to:

Explain the mechanisms of action, uses, and

adverse effects.

Identify the common sympathomimetic and

parasympathomimetic drugs used in the

Sultanate of Oman


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Objective 1

Explain the mechanisms of action,

uses, and adverse effects.


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Contents

A. Sympathomimetic drugsB. Asthma drugs (bronchodilators, corticosteroids,

sodium cromoglicate)

C. Adrenergic Blocking Agents

D. Parasympathomimetic drugs

E. Anticholinesterases

F. Synthetic atrophine like drugs

G. Drugs to prevent migraine


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Autonomic Nervous System

Autonomic

Nervous System

SympatheticNervous System

ParasympatheticNervous System

visceraGastrointestinal TractRespiratory and Urogenital

Heart and Blood vessels

Muscles of the eyes

Various secretory glands


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Effects of Sympathetic and Parasympathetic Activity

Sympathetic Activity Parasympathetic Activity

Heart Rate increased Slowed

Blood Vessels constricted Dilated

Stomach / Intestine Decreased activity and

secretion

Increased activity and

secretionSalivary / Bronchial glands Decreased secretion Increased secretion

Urinary bladder Body relaxed, sphincter

contracted

Body contracted, sphincter

relaxed

Bronchial muscle relaxed Contracted

Blood sugar raised

Eye Pupils dilated Pupils constricted,

accommodates for near

vision


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Chemical Transmission of Nerve Impulses

Neurotransmitter- a substance liberated

through a stimulation of a nerve ending,

which activates a receptor in the organsupplied or in another nerve cell.

Acetylcholine (ACh) in parasympathetic

Noradrenalinein sympathetic


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Receptor- proteins that occur at thesurface of the cell or inside it.

Purpose is to bind the bodys chemical

messengers and transmit the binding event into

a signal that the cell can recognize and respond

to.

Nicotinic and Muscarinic in Parasympathetic alpha 1, alpha 2, beta 1, beta 2 and beta 3 in

Sympathetic


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Parasympathetic System Acetylcholine Receptors: (Cholinergic)

After stimulation of the neurotransmitter,

acetylcholine (ACh), it acts on a cholinergic

receptor on the organ supplied by the nerve.

To prevent the effect of acetylcholine (ACh) being

too prolonged and powerful,acetylcholineseterase, which is also present at the

nerve endings, rapidly breaks down the

acetylcholine and terminates its effect.


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Sympathetic System

Adrenergic Receptors:

a1 receptors-these receptors are

stimulated by noradrenaline and adrenaline

produces constriction of blood vessels, causing

rise in blood pressure and reflex slowing of the

heart and dilatation of the pupil


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Effects of adrenoreceptors: (Cont) a2receptors- when noradrenaline binds

with them, they limit further release of

noradrenaline, thus, forming a releasecontrol mechanism to inhibit further

release of noradrenaline, and therefore,

useful to treat hypertension.


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Effects of adrenoreceptors: (Cont) b and b2 receptors- these receptors are

stimulated by isoprenaline and adrenaline

(epinephrine);

The effects are:

b increase in rate and excitability of the heart

with increased cardiac output

b2 responsesdilatation of bronchi and bloodvessels


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B3 receptors - present in cardiac muscle;inotropic (depress the rate and force of

contraction)


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Chemical Transmission of Nerve ImpulsesAutonomic Nervous

System

Neurotransmitter

Preganglionic

neuron

Neurotransmitter

Postganglionic

neuron

Receptors on

Target tissue

Sympathetic Acetylcholine (ACh) Noradrenaline Adrenergic

Receptor

(a and b )Parasympathetic Acetylcholine (ACh) Acetylcholine Cholinergic

Muscarinic

Receptor


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Chemical Transmission of Nerve ImpulsesAutonomic Nervous

System

Neurotransmitter

Preganglionic

neuron

Receptors on

Target tissue

Sympathetic Acetylcholine

(ACh)

Adrenergic

Receptor

(a and b )

Parasympathetic Acetylcholine

(ACh)

Cholinergic

Muscarinic

Receptor


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Sympathomimetic Drugs

Sympathomimetic drugshave similar effects to

those produced by activity of the sympathetic

nervous system and comprise:

Adrenaline Noradrenaline

Isoprenaline

Selective b2 agonists


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Sympathomimetic Drugs1. Adrenaline (epinephrine)

Mechanism of Action:

Released from the medulla of the adrenal gland

when sympathetic system is activated

Acts on the sympathetic receptors of the visceral

organs (alpha and beta)

It is prepared synthetically

Destroyed by gastric acid, not effective to be takenorally


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Sympathomimetic Drugs Adrenaline (epinephrine)


Given by subcutaneous or intramuscular injection

Effects are more pronounced via IM site


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Adrenaline (epinephrine) (cont)

Uses/Effects:

b1 effects: increase in the force and rate of contraction

of the heart

Rise in systolic blood pressure due to

increased cardiac output


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Adrenaline (epinephrine) (cont)

Uses/Effects:

Relaxes smooth muscle, including that ofbronchial tree (b2 effect).

Raises blood sugar by mobilizing glucose

from tissues

Following injection, it is rapidly broken

down by the enzymes and effects last for

only a few minutes


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Adverse Effects:

Adrenaline (epinephrine) is given as an

intravenous bolus in small doses as a

stimulant to the heart in cardiac arrest. It is essential not to inject larger doses into a

vein by mistake for this can precipitatefatal

cardiac arrhythmia.


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2. Noradrenaline (norepinephrine) Chemically closely related to adrenaline

(noradrenaline)

Mechanism of Action: Noradrenaline acts on both alpha-1

and alpha-2adrenoreceptors to cause

vasoconstriction


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Sympathomimetic Drugs2.Noradrenaline (norepinephrine)

Uses/Effects:

Widespread vasoconstriction and thus, a rise in

both systolic and diastolic blood pressure (alpha-1

effect)

It is given by intravenous infusion


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Sympathomimetic Drugs2. Noradrenaline (norepinephrine)

Uses/Effects:

Used in the treatment of various forms of

shock, which is usually associated with avery low blood pressure


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Adverse Effects:

Opinion has moved against using noradrenaline to

raise blood pressure except in extreme

circumstances, for although a satisfying rise inblood pressure can be obtained due to

vasoconstriction, this also reduces the blood flow

to essential organs, esp. the kidney, with

troublesome results.


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Adverse Effects: Nursing Point

A patient receiving noradrenaline (norepinephrine)

requires careful nursing monitoring and

assessmentbecause blood pressure may fluctuatewidely with small changes in the rate of infusion.

Care should be taken to avoid extravasation, which

can cause necrosis.
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Sympathomimetic Drugs3. Isoprenaline

Synthetic drug related to adrenaline

Well absorbed from the oral mucosa and following

inhalation

It is rapidly inactivated after absorption and its

effects are short lived.

Can also be given by infusion in severe bradycardia


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Sympathomimetic Drugs3.Isoprenaline


isoprenaline stimulates beta-1 and beta-2

receptorsbut not alpha receptors


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Sympathomimetic Drugs3. Isoprenaline

Uses:

Relaxes smooth muscle, including that of the

bronchial tree stimulates the heart, but has little or no

effect on the blood pressure


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Sympathomimetic Drugs3.Isoprenaline

Adverse Effects:

Avoid overdose as it can cause dangerous cardiac

arrythmias

Palpitation, nausea, headaches and tremors


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Sympathomimetic Drugs4. Selective beta-2 Agonists

Mechanism of Action

Stimulate predominantly beta-2 receptors,

results in relaxation of bronchial smooth muscles.

- although they are effective bronchodilators, they

have minimal effects on the heart


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Sympathomimetic Drugs4. Selective beta-2 Agonists (cont)

A. Salbutamol (short-acting)

The most widely used beta-2 agonist

Powerful bronchodilator

Action lasts about 4 hours

Can be given in various routes, but if given orally,

a considerable proportion is broken down in the

liver (first pass effect).


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A. Salbutamol

Inhalationmost common route

Maximum effect on the bronchi than elsewhere

Even so, only 10% of the dose reaches the

bronchial tree because the rest is being

swallowed


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A. Salbutamol

Orally3-4 times daily

Large dose should be given because of the first

pass effect (metabolize in the liver)


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A. Salbutamol

Slowly by IV route

Treat severe asthma attack, though it is rare

because as a nebulizer is usually very effective

Salbutamol IV requires careful monitoring for

cardiac arrythmias


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4. Selective beta-2 Agonists (cont) Salbutamol

Uses / Effects:

Treat bronchospasms due to asthma or bronchitis

It may be taken to relieve an attack or, on a

regular basis, control spasm.

It can also be used to inhibit premature labor and

treat hyperkalemia

Terbutaline, fenoterol, reproterol and babuterol

are other selective beta-2 agonists


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Sympathomimetic Drugs4. Selective beta-2 Agonists(cont)

Salbutamol

Adverse Effects:

In large doses, it can cause tremor and

tachycardia and occasionally night cramps


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Salmeterol and Eformeterol

Long-acting beta-2 agonists

Effective after about 30 mins and their action lasts

for about 12 hours; therefore, should not be used for

rapid effect in treating acute attack, but given 2x/day,

by inhalation, as a preventive


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Salmeterol and Eformeterol

Claimed to have anti-inflammatory action as well as

relieving bronchospasm, but still is controversial

Can be combined with an inhaled steroid


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Asthma DrugsA. Bronchodilators

Inhaled beta-2 agonists

Oral beta-2 agonists

Methylxanthines

Anticholinergic drugs

B. Corticosteroids

C. Sodium Cromoglicate


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1. Inhaled beta-2 agonists

Widely prescribed

Given by inhalation to treat a developing attack

or prevent attack (exercise-induced asthma)

Dont control the inflammatory component of

asthma and there is evidence that regular use

can lead ultimately to more severe andsometimes fatal attack

Corticosteroid can be added to a regular use of

beta-2 agonist to control asthma


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Asthma Drugs

A. Bronchodilators2. oral beta-2 agonists Salbutamol tablets are not very efficient, but

salbutamol control-release tablets, at a dose of

one a night, have a prolonged action and areuseful in preventing nocturnal attacks ofasthma

3. Methylxanthines

relax and relieve spasm


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Asthma Drugs

A. Bronchodilators3. Methylxanthines (cont) Aminophylline and theophylline , though they

are effective, they require careful use, as there

is only small difference between thetherapeutic and toxic dose.


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3. Methylxanthines (cont)

Aminophyllinecan be given slow IV to

terminate acute attack

Can be given as loading dose followed by an

infusion by pump

Plasma levels should be measured at intervals

if to be given prolonged as a guide to dosage High plasma levels may result if oral and IV

administration are combined and this can be

dangerous


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Always ask if the patient is taking a

methylxanthine orally before giving

intravenous

Adverse Effects:

Dose related and include nausea, anxiety,

tachycardia, arrhythmias and convulsions


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Interactions are common and effects are

increased by cimetidine, erythromycin and oralcontraceptives


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Asthma Drugs

A. Bronchodilators4. Anticholinergic Drugs- Ipratropium bromiderelated to atropine


Anticholinergic agent, and acts as bronchodilator


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4. Anticholinergic Drugs

- Ipratropium bromide (cont)

- Given via inhaler or nebulizer

- Any of the drug that is swallowed is not absorbed

from the intestine

- It should be used for those patients who have not

responded to beta-2 agonists


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4. Anticholinergic Drugs (cont)

- Ipratropium bromide

- Effects begin after 45 minutes and lasts 3-4 hours;

therefore, has to be taken to prevent asthma attack

- Can be combined with a beta-2 agonist or

corticosteroid


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4. Anticholinergic Drugs (cont)

- Ipratropium bromide

- Adverse Effects:

- Unpleasant taste and dry mouth due to blocking of

salivation


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Asthma Drugs

B. Corticosteroids (Steroids)- Reduce inflammation and allergic aspects of asthma

and decrease bronchospasm in severe and

persistent asthma

- Beclamethasone(steroid that is well absorbed from

mucous surfaces) can be given by inhalation


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Asthma DrugsB. Corticosteroids (Steroids) cont

- Fluticasonehas the same benefits with less

systemic effects

- Occasional candida infection of the mouth may

occur, presumably due to the lowering of localresistance by the steroid

- Hoarse voice may occur due to weakening of voice

chords


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Asthma DrugsB. Corticosteroids (Steroids) cont

- These effects usually disappears when the drug is

stopped or the dose is reduced.

- In a few resistant case of asthma, oral prednisone

will be required, at the minimal effective dose


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Asthma DrugsC. Sodium Cromoglicate

- Mechanism of Action:

- Prevents asthmatic attack by stopping the release

of histamine from bronchial mast cells that are

responsible for bronchospasm.


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Pressurized aerosol or rotahaler


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- Given regularly by pressurized aerosol or rotahaler.

- Usual dose is four inhalations daily

- Most effective in young patients with an allergic

history of asthma and is of some use in non-allergicasthma


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- Nedocromilalso a mast cell stabilizer and anti-

inflammatory drug, and is very similar to sodium

cromoglicate

- Given as a pressurized aerosol and is used toprevent rather than treat attacks


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Asthma DrugsD. Leukotrienes Modifiers


- Leukotrienesare substances produced by leucocytes

involved in the inflammatory response and which

cause spasm of the bronchial muscle


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- Leukotriene modifiers prevent spasm either by

blocking the action of leukotrienes or by preventing

inflammation.


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- They also diminish hyperactivity of the bronchial

mucosa and reduce inflammation.

- Zileuton, Montelukast and Zafirlukast (block

leukotriene receptors)


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Montelukast, can be given orally to adults and

children over age 6.

At present it is used as a continuous treatment for

mild-to-moderate asthma and may reduce the needfor other drugs.

It is also useful in preventing exercise-induced

asthma

Adrenergic Blocking Agents


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it is possible to block alpha and beta- adrenergic

receptors selectively

Alpha-1 adrenergic blocker

uses: hypertension and bladder neckobstruction


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Adrenergic Blocking AgentsAdrenergic Blocking Agents (cont)


Hypertension : blocks the vasoconstrictor action of

noradrenaline causing dilatation of arterioles and

lowering blood pressure


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Bladder Neck Obstruction:

-Alpha-1 adrenergic receptors control the smooth

muscle round the neck of the bladder


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Bladder Neck Obstruction: cont

- By blocking these receptors it is possible to relax this

muscle and partially relieve bladder neck obstructiondue to an enlarged prostate


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Beta Adrenergic Blockers


block the effects of adrenaline and noradrenaline

on beta-adrenergic receptors


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Beta Adrenergic Blockers-Widely used and more important than the

alpha-blocking drugs

-have the same effects and uses but with minor

differences:


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Adrenergic Blocking Agents General Actions of Beta-blockers

Cardiovascular Actions: When 1 receptors in the heart are blocked, the

heart rate is slowed, the cardiac output is reduced

and the work done by the heart is thus

decreased.


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Adrenergic Blocking Agents General Actions of Beta-blockers

Cardiovascular Actions:

In addition, the excitability of heart muscle is

reduced.

-Blockers lower blood pressure


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General Actions of Beta-blockers

Respiratory Actions:

Blocking 2 receptors with -blockers cause

bronchospasm, particularly in patients withasthma.

This is particularly marked with non-selective

-blockers such as propanolol.

This is usually of little consequence in healthy

people, but in patients with asthma it may

make bronchospasm worse and increase

dyspnea.


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Metabolic Actions:

Some -blockers prevent the rise in blood

glucose which normally follows increasedsympathetic activity.


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CNS Actions:

Some sedation is fairly common in patients

receiving -blockers and occasionally this maybe severe.

In addition, vivid dreams and, more rarely,

hallucinations may occur.

d l k


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Uses:

Angina of effort because they reduce the work

of the heart, especially on effort or

excitement. Cardiac arrhythmias, because they reduce the

excitability of the heart.

Hypertension, as they lower blood pressure,

perhaps by setting the regulation of blood

pressure at a lower level.

d i l ki


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Uses:

Thyrotoxicosis and anxiety, because they

reduce the increased sympathetic activity

which occurs in these disorders. Essential tremor, a rare familial condition

characterized by severe intention tremor.

Prevention of migraine attacks

Ad i Bl ki A


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Adverse Effects:

exacerbation of heart failure

Occasionally cause vivid dreams and

hallucinations, decreasing cardiac output, they reduce the

blood flow to the extremities, causing the

patient to feel cold, and are best avoided in

peripheral vascular disease.

Ad i Bl ki A


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Adverse Effects:

They mask the usual warning symptoms of

hypoglycemia and can be dangerous in

patients with diabetes who are taking insulin. Active people may feel less energetic whilst

taking these drugs

Parasympathomimetic


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Parasympathomimetic

Drugs Parasympathomimetic drugs have effects

similar to those produced by activity of the

parasympathetic nervous system. Examples

are:

Acetylcholine

Carbachol

Bethanechol

Pilocarpine

Parasympathomimetic


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Parasympathomimetic

Drugs Acetylcholine

acetylcholine activates voluntary muscle when a

motor nerve is stimulated and is essential for all

voluntary movements. Its action is very short lived, as it is quickly

broken down by cholinesterase to choline and

acetate, so it is not used therapeutically.

Parasympathomimetic


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Parasympathomimetic

Drugs Acetylcholine cont

However, a prolonged effect can be produced either

by giving an acetylcholine-like drug which is not

broken down or by using a drug which inhibits theaction of cholinesterase, thus prolonging and

intensifying the actions of naturally occurring

acetylcholine.

This type of drug is called an anticholinesterase

Parasympathomimetic


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Drugs Carbachol

Carbacholis a synthetic substance chemically related

to acetylcholine.

Its actions resemble those of parasympatheticstimulation.

It is not broken down by the body cholinesterases

and its actions are therefore much more prolonged

than those of acetylcholine.

Parasympathomimetic


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Drugs Carbachol Uses:

The most important therapeutic use of carbachol is

in the treatment of urinary retentionfollowing

surgical operation or childbirth when there is nomechanical obstruction.

It causes contractionof the bladder muscle, resulting

in the passage of urine

Parasympathomimetic


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Drugs Administration and Effects of carbachol after

injection

Carbachol may be given by subcutaneous injection or

by mouth.

After subcutaneous injection, flushing and sweating

appear in about 20 minutes, followed by increased

intestinal peristalsis, sometimes with colic, and

contraction of the bladder muscle. These actions last up to an hour.

Parasympathomimetic


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Drugs Adverse Effects

include colic, diarrhoea and a marked fall in blood

pressure.

These adverse effects are controlled by atropine.

Parasympathomimetic


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Drugs

Bethanechol

Bethanecholis another acetylcholine-like drug,

which, like carbachol, is not broken down by

cholinesterase.

Parasympathomimetic


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Drugs Pilocarpine

Pilocarpineis used only as eye drops, where it

causes constriction of the pupil

A ti h li t


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Anticholinesterases

These drugs prevent the breakdown of acetylcholineby cholinesterase produced at nerve endings

throughout the body.

Anticholinesterases


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Anticholinesterases Important Effects

The eye: absorbed through the conjunctiva and

following application to the eye cause constriction

of the pupil and spasm of accommodation.

Gastrointestinal tract: cause increased tone andmotility.

Urinary tract: cause contraction of the bladder.

Anticholinesterases


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Anticholinesterases Clinically-used anticholinesterases

Several anticholinesterases are used to treat a

variety of disorders, depending on where their

actions are most pronounced:

neostigmine physostigmine

pyridostigmine

edrophonium distigmine.

Anticholinesterases


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Anticholinesterases Clinically-used anticholinesterases (cont)

Neostigmineis a synthetic anticholinesterase with

actions very similar to those of physostigmine, but

with an effect on the neuromuscular junction of

voluntary muscle and less on the eye andcardiovascular system.

It is rapidly effective following subcutaneous or

intramuscular injection and is also absorbed after

oral administration, although this route requires

larger doses.

Anticholinesterases


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Anticholinesterases Uses of Neostigmine:

Neostigmine is used widely in the treatment of

disorders of the voluntary muscle (e.g. myasthenia

gravis*), and has been used in cases of paralytic

ileusand atony of the bladder. *Myasthenia gravisa form of muscular

paralysis through Ach receptor failure

Anticholinesterases


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Anticholinesterases Uses of Neostigmine:

Pyridostigmine and edrophonium are

anticholinesterases used in the treatment of

myasthenia gravis.

Edrophonium has a very short-lived action. Distigminehas widespread actions and may also

be used for urinary retention and myasthenia

gravis.

It can be given orally or by injection.

Anticholinesterases


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Anticholinesterases Adverse Effects:

intestinal colic and diarrhoea

sweating and salivation

pupils are constricted

pulse slow

blood pressure low.

Treatment: The immediate treatment is atropinegiven intravenously

Synthetic Atropine-like


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Drugs shorten the duration of action of the drug, e.g.

tropicamide for use in the eye, or to target certain

specific subtypes of the muscarinic receptor.

For example, trihexyphenidylis used clinically totreat Parkinson's disease since it is claimed

selectively to target M1 muscarinic receptors in the

brain.

Synthetic Atropine-like


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Drugs Among those available are:

dicycloverine

mebeverine

propantheline

oxybutynin

flavoxate

Drug to Prevent Migraine


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Drug to Prevent Migraine Drugs used to prevent migraine attacks:

-blockers

pizotifen

sodium valproate

antidepressants

methysergide



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-Blockersprevent or reduce attacks in about half of

the patients.

They probably act by reducing vasodilation

When they are prescribed, their contraindicationsmust be remembered and they should not be

combined with ergotamine.



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Pizotifen

prevents migraine attacks by reducing the

constriction and dilatation of blood vessels.

It can cause drowsiness and the initial dose shouldbe given at night.

Its main adverse effect is weight gain and it may take

up to a month to be effective.



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Sodium valproate

is an antiepileptic agent that can also be used to

prevent migraine attacks.

It should not be used in pregnancy, owing to the riskof fetal malformation



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Antidepressants

Dosulepin and amitriptyline are effective, even if the

patient is not suffering from depression



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Methysergide

Methysergide blocks the effects of 5-HT (serotonin)

on receptors in smooth muscle leading to

vasoconstriction. It is effective but has serious adverse effects and

should only be used when safer treatment has failed.

Anti-Migraine Drugs Used in Oman


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Major Classification Sub

classification

Examples or Drugs Used in

Oman

Anti-migraine Ergotamine tartrate and

caffeine

Flunarizine hydrochloride

NaratriptanRizatriptan

Sumatriptan succinate

zolmitriptan



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Major

Classification

Sub classification Examples or Drugs

Used in Oman

Antiepileptic For grandmal and

partial

seizures

Carbamazine

Clonazepam

Ethosuximide

GabapentinLeveitracetam

Phenobarbital /

phenobarbitone

Phenytoin sodium

Sodium valproateTopiramate

Patient and Family Education


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Migraine Drugs

1. Take medication at onset of pain, when

possible, to prevent development of more

severe symptoms

2. With triptans, take oral drugs with fluids. If

symptoms recur, a second dose may be taken.

However, do not take a second dose of

sumatriptansooner than 2 hours after the firstdose. Do not take more than 300mg of

sumatriptanin any 24 hour period.



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Migraine Drugs

3. Sumatriptan can be taken by mouth,

injection, or nasal spray. Do not take more than

40 mg of nasal spray in any 24-hour period. If

self-administering injectable sumatriptan, be

sure to give in fatty tissue under the skin.

4. With ergot preparation, reports signs of

vascular insufficiency, such as tingling sensationor coldness, numbness, or weakness of the

extremities. These are symptoms of ergot

toxicity.


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Drugs Acting on the Autonomic Nervous System