Chapter 5 Autonomic Drugs Mosby items and derived

Autonomic Pharmacology Autonomic Nervous System This system is divided into two separate systems. Ø These systems are called the parasympathetic nervous system and the sympathetic nervous system. Ø These systems often produce opposite effects. Ø 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. Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 2

Autonomic Nervous System Parasympathetic Nervous System This system is concerned with the conservation of the body processes. Ø Its main neurotransmitter is acetylcholine. Ø Its receptors are muscarinic, nicotinic, and the somatic-skeletal muscles. Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 3

Autonomic Nervous System Sympathetic Nervous System This nervous system is designed to cope with emergency situations. Ø This is commonly known as the “fright or flight” response. Ø Its neurotransmitters are epinephrine and norepinephrine. Ø Its receptors are the α and β receptors. Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 4

Autonomic Pharmacology Cholinergic or Parasympathomimetic Drugs These drugs are classified as either direct or indirect acting agents. Ø Direct acting drugs act directly on the parasympathetic receptors. Ø Indirect acting drugs work by either of two methods. Ø They can cause the release of the neurotransmitter which then goes to the receptor site or they inhibit the enzyme cholinesterase. Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 5

Autonomic Pharmacology Cholinergic Pharmacology Ø 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. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 6

Autonomic Pharmacology Cholinergic Pharmacology Ø Gastrointestinal • These drugs excite the smooth muscle of the gastrointestinal tract and cause an increase in activity, motility, and secretion. Ø Eye • These drugs cause miosis and cycloplegia. • They cause a decrease in intraocular pressure. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 7

Autonomic Pharmacology Adverse Reactions Adverse reactions are an extension of the drugs’ pharmacologic effects. Ø They include: • Salivation • Lacrimation • Urination • Defecation • Paralysis • Overdose Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 8

Cholinergic Pharmacology Contraindications The contraindications and relative cautions are a result of the drug’s pharmacologic and adverse effects. Ø They include: • Bronchial asthma • Hyperthyroidism • Gastrointestinal or urinary tract obstruction • Myasthenia gravis treated with neostigmine • Peptic ulcer disease • Severe cardiac disease Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 9

Cholinergic Drugs Mosby items and derived items © 2007 by Mosby, Inc. , an

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. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 11

Anticholinergic Drugs Pharmacology Ø Central Nervous System • Depending on the dose, these drugs can cause stimulation or depression. Ø Exocrine Glands • They reduce the flow and volume of secretions in the respiratory, gastrointestinal, and genitourinary tracts. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 12

Anticholinergic Drugs Pharmacology Ø 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. Ø Eye • These drugs cause mydriasis and cycloplegia. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 13

Anticholinergic Drugs Pharmacology Ø Cardiovascular • With large doses, these drugs produce vagal blocking which results in tachycardia. • Bradycardia can occur with low doses. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 14

Anticholinergic Drugs Adverse Reactions The adverse reactions are an extension of the drugs’ pharmacologic effects. Ø They include: • Xerostomia • Constipation • Urinary retention • Blurred vision • Hyperpyrexia • Hallucinations • Photophobia • Tachycardia Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 15

Anticholinergic Drugs Contraindications are usually due to the drugs’ pharmacologic and adverse effects. Ø They include: • Glaucoma • Prostatic hypertrophy • Intestinal or urinary obstruction or retention • Cardiovascular disease Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 16

Anticholinergic Drugs Uses Ø Preoperative Medication • They inhibit salivary and bronchial secretions. • They block the vagal slowing of the heart that can occur with general anesthesia. Ø Gastrointestinal Disorders • They decrease gastrointestinal motility and can be used to treat ulcers, diarrhea, and hypermotility. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 17

Anticholinergic Drugs Uses Ø 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. Ø Parkinson Disease • They reduce the tremors and rigidity associated with Parkinson and drug-induced Parkinson disease. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 18

Anticholinergic Drugs Uses Ø Motion Sickness • These drugs are used to treat or prevent motion sickness because of their central nervous system depressant action. Ø Dentistry • These drugs are used to create a dry, oral field. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 19

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. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 20

Adrenergic Drugs Pharmacology Ø Central Nervous System (CNS) • These drugs produce CNS excitation or alertness. • Higher doses produce anxiety, apprehension, restlessness, and tremors. Ø 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. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 21

Adrenergic Drugs Pharmacology Ø Eye • These drugs lower intraocular pressure and can cause mydriasis. Ø Respiratory System • These drugs cause a relaxation of bronchiole smooth muscles. Ø Metabolic Effects • Increased glycogenolysis from β-receptor stimulation causes hyperglycemia. Ø Salivary Glands • These drugs produce vasoconstriction of the salivary glands which leads to decreased salivary flow which results in xerostomia. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 22

Adrenergic Drugs Adverse Reactions The adverse reactions associated with these drugs are an extension of the drugs’ pharmacologic effects. Ø They include: • Anxiety • Tremors • Tachycardia • Increased blood pressure • Arrhythmias Ø Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 23

Adrenergic Drugs Uses Ø 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. Ø Cardiac Effects • These drugs are used to raise blood pressure and to treat cardiac arrest. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 24

Adrenergic Drugs Uses Ø Bronchodilation • These drugs are used to treat asthma, emphysema, and allergic reaction. Ø Central Nervous System Stimulation • These medications are used for the treatment of attention deficit hyperactivity disorder, narcolepsy, and as diet aids. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 25

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 β 1 and β 2 receptors. One group is specific for both α and β receptors. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 26

Antiadrenergic Drugs Pharmacology These drugs reduce sympathetic tone in the blood vessels and decrease total peripheral resistance. Ø This results in a reduction in blood pressure. Ø Uses Ø These drugs are used to treat hypertension, peripheral vascular disease (i. e. , Raynaud syndrome) and benign prostatic hypertrophy. Mosby items and derived items © 2007 by Mosby, Inc. , an affiliate of Elsevier Inc. 27