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AUTONOMIC NERVOUS SYSTEM

LECTURE 6PHARMACOLOGY

Autonomic Pharmacology

• Autonomic Nervous System– This system is divided into two separate systems.– These systems are called the parasympathetic

nervous system and the sympathetic nervous system.– These systems often produce opposite effects.– Drugs in this group are designed to either enhance or

mimic the autonomic nervous system or to block the effects of the neurotransmitters at their receptor sites.

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Autonomic Nervous System

• Parasympathetic Nervous System– This system is concerned with the

conservation of the body processes.– Its main neurotransmitter is acetylcholine.– Its receptors are muscarinic, nicotinic, and

the somatic-skeletal muscles.

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Autonomic Nervous System

• Sympathetic Nervous System– This nervous system is designed to cope

with emergency situations. – This is commonly known as the “fright or

flight” response.– Its neurotransmitters are epinephrine and

norepinephrine.– Its receptors are the α and β receptors.

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Autonomic Pharmacology

• Cholinergic or Parasympathomimetic Drugs– These drugs are classified as either direct or indirect acting

agents.– Direct acting drugs act directly on the parasympathetic

receptors.– Indirect acting drugs work by either of two methods.– They can cause the release of the neurotransmitter which

then goes to the receptor site or they inhibit the enzyme cholinesterase.

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PHYSIOLOGICAL FUNCTIONS

Autonomic Pharmacology

• Cholinergic Pharmacology– Cardiovascular

• Direct effects include negative chronotropic and inotropic actions.

• Relaxation of smooth muscles causes a decrease in total peripheral resistance.

• Indirect effects include increased heart rate and cardiac output.

• The resulting effect depends upon the dose used.• Usually, the patient experiences bradycardia and a

decrease in blood pressure and cardiac output.

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Autonomic Pharmacology

• Cholinergic Pharmacology– Gastrointestinal• These drugs excite the smooth muscle of the

gastrointestinal tract and cause an increase in activity, motility, and secretion.

– Eye• These drugs cause miosis and cycloplegia.• They cause a decrease in intraocular pressure.

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Autonomic Pharmacology

• Adverse Reactions– Adverse reactions are an extension of the

drugs’ pharmacologic effects.– They include:• Salivation• Lacrimation• Urination • Defecation• Paralysis• Overdose

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Cholinergic Pharmacology

• Contraindications– The contraindications and relative cautions are

a result of the drug’s pharmacologic and adverse effects.

– They include:• Bronchial asthma• Hyperthyroidism• Gastrointestinal or urinary tract obstruction• Myasthenia gravis treated with neostigmine• Peptic ulcer disease• Severe cardiac disease

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Cholinergic Drugs

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Anticholinergic Drugs

• These drugs prevent the action of acetylcholine at postganglionic parasympathetic endings.

• Acetylcholine is released but its receptor site is completely blocked by anticholinergic drugs.

• These drugs only block muscarinic receptors.

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Anticholinergic Drugs

• Pharmacology– Central Nervous System• Depending on the dose, these drugs can cause

stimulation or depression.

– Exocrine Glands• They reduce the flow and volume of secretions

in the respiratory, gastrointestinal, and genitourinary tracts.

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Anticholinergic Drugs

• Pharmacology– Smooth Muscle• Relax smooth muscles in the respiratory and

gastrointestinal tracts. • They delay gastric emptying and decrease

esophageal and gastric emptying.• These drugs also cause bronchial dilation.

– Eye• These drugs cause mydriasis and cycloplegia.

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Anticholinergic Drugs

• Pharmacology– Cardiovascular• With large doses, these drugs produce vagal

blocking which results in tachycardia.• Bradycardia can occur with low doses.

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Anticholinergic Drugs

• Adverse Reactions– The adverse reactions are an extension of

the drugs’ pharmacologic effects.– They include:• Xerostomia• Constipation• Urinary retention• Blurred vision• Hyperpyrexia• Hallucinations• Photophobia• Tachycardia

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Anticholinergic Drugs

• Contraindications– Contraindications are usually due to the

drugs’ pharmacologic and adverse effects.– They include:• Glaucoma• Prostatic hypertrophy• Intestinal or urinary obstruction or retention• Cardiovascular disease

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Anticholinergic Drugs

• Uses– Preoperative Medication• They inhibit salivary and bronchial secretions.• They block the vagal slowing of the heart that

can occur with general anesthesia.

– Gastrointestinal Disorders• They decrease gastrointestinal motility and can

be used to treat ulcers, diarrhea, and hypermotility.

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Anticholinergic Drugs

• Uses– Ophthalmologic Examinations• Topical use can cause mydriasis which causes a

full visualization of the retina.• Cycloplegia relaxes the lens so that proper

prescriptions for glasses can be determined.

– Parkinson Disease• They reduce the tremors and rigidity associated

with Parkinson and drug-induced Parkinson disease.

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Anticholinergic Drugs

• Uses– Motion Sickness• These drugs are used to treat or prevent motion

sickness because of their central nervous system depressant action.

– Dentistry• These drugs are used to create a dry, oral field.

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Adrenergic Drugs• Adrenergic drugs can be classified as having direct action,

indirect action, or mixed action.• These drugs stimulate α and β receptors throughout the

body.• Drugs with direct action (epinephrine, norepinephrine,

isoproterenol) produce their effect by directly stimulating the receptor site.

• Drugs with indirect action (amphetamine) release endogenous norepinephrine which then stimulates the receptor.

• Drugs with mixed action (ephedrine) either directly stimulate the receptor or release endogenous norepinephrine.

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Adrenergic Drugs

• Pharmacology– Central Nervous System (CNS)

• These drugs produce CNS excitation or alertness.• Higher doses produce anxiety, apprehension,

restlessness, and tremors.

– Cardiovascular System• These drugs increase the force and rate of

contraction of the heart. • Blood pressure is also increased.• Total peripheral resistance is also increased.

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Adrenergic Drugs• Pharmacology– Eye

• These drugs lower intraocular pressure and can cause mydriasis.

– Respiratory System• These drugs cause a relaxation of bronchiole smooth

muscles.– Metabolic Effects

• Increased glycogenolysis from β-receptor stimulation causes hyperglycemia.

– Salivary Glands• These drugs produce vasoconstriction of the salivary

glands which leads to decreased salivary flow which results in xerostomia.

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Adrenergic Drugs

• Adverse Reactions– The adverse reactions associated with these

drugs are an extension of the drugs’ pharmacologic effects.

– They include:• Anxiety• Tremors• Tachycardia• Increased blood pressure• Arrhythmias

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Adrenergic Drugs

• Uses– Vasoconstriction• These drugs are used in dentistry because of

their vasoconstrictive actions on blood vessels. They are added to local anesthetics because they prolong the action of the local anesthetic, reduce the risk for systemic toxicity, and help to create a dry field.

– Cardiac Effects• These drugs are used to raise blood pressure

and to treat cardiac arrest.

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Adrenergic Drugs

• Uses– Bronchodilation• These drugs are used to treat asthma,

emphysema, and allergic reaction.

– Central Nervous System Stimulation• These medications are used for the treatment of

attention deficit hyperactivity disorder, narcolepsy, and as diet aids.

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Adrenergic Blocking Drugs

• These drugs competitively inhibit α and β receptor sites.

• One group of drugs is specific for α receptors.

• One group of drugs is specific for both β1 and β2 receptors.

• One group is specific for β2 receptors.• One group is specific for both α and β

receptors.26

Antiadrenergic Drugs

• Pharmacology– These drugs reduce sympathetic tone in the

blood vessels and decrease total peripheral resistance.

– This results in a reduction in blood pressure.• Uses– These drugs are used to treat hypertension,

peripheral vascular disease (i.e., Raynaud syndrome) and benign prostatic hypertrophy.

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PARASYMPATHOMIMETICS

• Acetyl Choline• Chols (Bethanecol, Carbe)• Pilocarpine• Stigmines (Physio,Pyrido and Neo)• Pralidoxine

PARASYMPATHOLYTICS

• Atropine• Ipratropium• Scopolamine• Nicotine• Atra and Doxacurium

SYMPATHOMIMETICS

• Albuterol• Dolbutamine, Dopamine*• Epi*/ Norepinephrine*• Isoproterenol*• Amphetamine• Ephedrine*catecholamines

Same drugs different receptors

SYMPATHOLYTICS

• Prazosin• Lols- Atenolol, Propranolol• Cocaine• Reserpine

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