chapters 3 and 4 pathology

Chapter 3

Introduction to Basic Pharmacology and Other Common Therapies

•2•Copyright © 2014, 2011, 2006 by Saunders, an imprint of Elsevier, Inc.

Pharmacology

Integrated medical science involving chemistry, biochemistry, anatomy, physiology, microbiology, and more

Study of drugs, their actions, dosage, therapeutic uses, adverse effects

Drug therapy is directly linked to the pathophysiology of a particular disease.

Drugs may come from natural sources. Plants, animals, microorganisms

Drugs also may be synthesized.


Drugs

Promote healing Anti-inflammatory

Cure disease Antibacterial

Control or slow progress of a disease Cancer chemotherapy

Prevent disease Vaccine


Drugs (Cont.)

Alter neurotransmission Antidepressants

Decrease risk of complications Anticoagulants

Increase function and comfort Analgesics for pain

Provide replacement therapy Insulin

Reduce excessive activity in the body Proton pump inhibitors


Disciplines of Pharmacology

Pharmacodynamics

Pharmacokinetics

Pharmacotherapeutics

Toxicology

Pharmacy


Drug Effects

Therapeutic (desired) action may be: Stimulating or inhibiting cell function Blocking biochemical actions in tissues

Classification Grouped by their primary pharmacologic action

and effect Indications

Approved for uses to treat conditions for which the drug has been proved to be effective


Drug Effects (Cont.)

Generally, drugs possess more than one effect on the body.

Contraindications Circumstances under which a drug should not be

administered Side effects

Mild, undesirable effects of a drug, even at recommended dose

Adverse or toxic effects Drug effects that are dangerous, cause significant

tissue damage, or are life-threatening


Specific Adverse Drug Effects

Hypersensitivity―allergic reactions Reactions may be mild or can result in

anaphylaxis. Idiosyncratic reactions

Unusual responses to a drug Iatrogenic

Negative effect associated with administration of drug

Teratogenic Harmful effect on fetus, developmental defects


Specific Adverse Drug Effects (Cont.)

Interactions: drug effect modified by combination with another drug Synergism

• Effect of drug combination may be greater than the sum of the effects of the individual drugs.

Antagonism• Combination greatly decreases the effect of each drug.

Potentiation • One drug enhances the effect of a second drug.


Administration and Distribution of Drugs

Dose Amount of drug required to produce the desired

effect in adult Expressed by a weight or measure Expressed by time factor (e.g., twice a day)

Child’s dose Best calculated by child’s weight, not age

“Loading dose” Larger dose may be administered initially to raise

blood levels to an effective level


Administration and Distribution of Drugs (Cont.)

Frequency of dosing Important to maintain effective blood levels of the

drug without reaching toxic levels Optimum dosing schedule

Established for each drug based on• Absorption, transport in the blood, half-life of the drug

Timing Directions regarding

• Timing related to meals• Daily events• Sleep


Factors Affecting Blood Levels of Drugs

Regular intake, normal distribution and excretion


Factors Affecting Blood Levels of Drugs (Cont.)

Factors: taking drug at irregular intervals, missing doses


Factors Affecting Blood Levels of Drugs (Cont.)

Factors: taking double dose or too frequently


Factors Influencing Blood Levels of a Drug

Liver and kidney function Absorption and excretion

Circulation and cardiovascular function Age Body weight and proportion of fatty tissue Activity level, exercise Food and fluid intake Genetic factors Health status, presence of other diseases,

chronic or acute


Administration and Distribution of Drugs

Drugs can be administered for acting locally or have a systemic action.

Drug enters body by chosen route Absorbed into blood or acts at local site Travels in the bloodstream Arrives at site of action Exerts its effect Is metabolized into inactive compounds Is excreted from the body


Routes of Drug Administration

Oral tablet, capsule, liquid Sublingual Subcutaneous injection Intramuscular injection Intravenous injection Inhalation Topical (gel, cream, spray, liquid) Suppository


Administration and Distribution of Drugs (Cont.)

Some drugs can only be taken via one route. Oral medication

Absorbed from stomach or intestine Transported to the liver Released into general circulation

Intramuscular injection Gradually absorbed into the blood Blood transports drug


Drug Absorption, Distribution, and Excretion


Drug Mechanisms and Receptors

Common pharmacologic action requires drug-receptor interaction.

Drugs may stimulate receptors directly. Drugs may block receptor site for normal

chemicals of the body Specificity of drug dependent on mode of

action Drugs that interact with several metabolic

pathways or common functions are likely to have greater side effects.


Receptors and Drug Action


Prescriptions

Prescription―a signed legal document that must include the following: Patient’s name, address, and age (if significant) Prescriber’s name, address, and identification

number Date Name and amount of the drug Dosage Route and directions for using the drug Permission for additional quantities


Drug Nomenclature and Classification

Each drug has a generic name, a trade name, and a chemical name

Generic name: unique, official, simple name for a specific drug For example, ASA

Trade, proprietary, or brand name For example, aspirin

Chemical name: chemical component For example, acetylsalicylic acid


Examples of Drug Nomenclature


Drug Regulation

U.S. Food and Drug Administration*

Regulates the production, labeling, distribution, and other aspects of drug control

Scheduled drugs Drugs considered to have a risk for potential

adverse side effects, abuse, or dependency Over-the-counter (OTC) drugs

Available without prescription

*Food and Drug Directorate in Canada.


Traditional Forms of Therapy


Physiotherapy

Assesses physical function Works to reduce pain, restore any deficit and

prevent further physical dysfunction Involves individualized treatment and

rehabilitation Physiotherapy may include the following:

Appropriate exercise Use of ultrasound Transcutaneous electrical nerve stimulation

(TENS) Other methods to alleviate pain, increase function


Physiotherapist

Treats acute injuries as well as chronic conditions

Practice includes the following: Pain disorders Acute neurologic disorders Musculoskeletal disorders Cardiopulmonary disorders Infants with congenital abnormalities Children and adults with injuries that affect mobility


Occupational Therapist

Provides functional assessment related to normal activities of daily living

Provides guidance and practical assistance to maintain independence

Integrates remediation of motor control, cognition, and visual-spatial perception Necessary for patient safety

Teaches use of adaptations for specific needs

Assesses technologies available for use in home and workplace


Speech and Language Pathologist

Assesses and treats those with communication or swallowing problems

Patients may include the following: Infant with swallowing and feeding problems Child with hearing deficit who is mute Adult with aphasia following a stroke Child with delayed speech Individual with dysarthria


Nutritionist-Dietitian

Expert in nutritional needs of the body in health and illness

Advises on nutritional needs and food management suited to a specific diagnosis Example: diabetes

Supervises food services in hospitals and other health care institutions

May consult on the dangers of extreme diets and eating disorders


Registered Massage Therapist

Uses a variety of massage techniques to: Increase circulation Reduce pain Increase flexibility for patients with joint pain or

problems with body alignment May use:

• Soothing aromatics• Acupuncture• Other modalities


Osteopath

Osteopaths are medically licensed doctors in many jurisdictions.

Uses many medical treatment methods In addition, an osteopath:

Promotes body’s natural healing processes by incorporating manipulations of the musculoskeletal system (e.g., use of chest percussion to relief respiratory congestion)


Chiropractic

Based on the concept that one’s health status is dependent on the state of the nervous system

Frequently involves manipulations of the vertebral column

May involve deep tissue massage, acupressure, and/or acupuncture

Radiology may be used for diagnosis. No drugs or surgery


Complementary or Alternative Therapies


Principles

These therapies are used in conjunction with medically related therapies.

All practitioners should know about various therapies that the client is using.

Use of complementary therapy does not require abandoning medical therapy.


Noncontact Therapeutic Touch

Energy is exchanged between people for relief of pain and anxiety and to promote healing.

Consciously forms a positive intent to heal Location of problem areas by scanning body

with the hands Healing is promoted by lightly touching the skin or

moving the hands just above the body surface. Imagery, light, or colors may be incorporated.


Naturopathy

Treatment based on the following: Promoting natural foods Massage Exercise Fresh air Acupuncture Herbal compounds Nutrition Physical manipulations


Homeopathy

Goal is to stimulate the immune system and natural healing powers of the body by use of the following: Plant products Animal products Mineral products Offending toxic substance is identified for each

disease state.• Diluted several thousand-fold• The diluted toxin is then administered to treat the

problem.


Herbalism

First documented in ancient Egypt Use of herbs and plants for treatment of

acute conditions or prevention of disease Efforts are being focused on the following:

Providing standardized content Providing efficacy Improving purity


Aromatherapy

Uses essential oils that have therapeutic effects

Thought to act on neural pathways through the olfactory system

Oils may be Absorbed through the skin into the general

circulation• When bathing• With massage

Inhaled


Asian Concepts of Disease and Healing

Based on balance or imbalance of life energy―qi

Disease is caused by a deficit or excess of qi. Qi is derived from three sources:

Inherited or ancestral factors Food ingested Air breathed in

Qi flows along specific channels―meridians. All organs and body parts are connected.


Asian Concepts of Disease and Healing (Cont.)

Acupuncture Increases energy, function; blocks pain pathways Involves Inserting fine needles into the various

meridian acupoints (365)• Each point has specific and generalized therapeutic

actions. Treatment on average uses 5 to 15 needles.

Shiatsu Japanese―acupuncture without needles Uses slow, deep, gentle pressure to specific points Often used for stress-related illness and back pain;

provides relaxation



Yoga Combines physical activity in the form of stretching

postures with meditation Improves flexibility, muscle tone, endurance,

overall health; reduces stress Reflexology

Relates points on feet and hands to 10 longitudinal zones in the body

Practitioner uses varying degrees of pressure. Relieves stress and muscle tension



Craniosacral therapy Used by a variety of health care practitioners Therapy deals with the pulsing rhythm of

cerebrospinal fluid around brain and spinal cord Gentle palpation and manipulation of skull and

vertebrae Ayurveda

Special dietary plans, yoga, and herbal remedies are commonly used.

Balance of body factors results in healthy mind and body

Chapter 4

Pain


Pain

Unpleasant sensation Discomfort caused by stimulation of pain receptors

Body defense mechanism Warning of a problem

Complex mechanisms Many not totally understood

Subjective scales Developed to compare pain levels over time


Causes of Pain

Inflammation Infection Ischemia and tissue necrosis Stretching of tissue Stretching of tendons, ligaments, joint

capsule Chemicals Burns Muscle spasm


Somatic Versus Visceral Pain

Somatic pain From skin (cutaneous) Bone muscle Conducted by sensory fibers

Visceral pain Originates in organs Conducted by sympathetic fibers May be acute or chronic


Pain Pathways

Nociceptors (pain receptors) are free sensory nerve endings.

May be stimulated by: Temperature

• Extremes of temperature Chemicals

• Examples: acids, bradykinin, histamine, prostaglandin Physical means

• Example: pressure


Pain (Cont.)

Pain threshold Level of stimulation required to elicit a pain

response Usually does not vary among individuals

Pain tolerance Ability to cope with pain Culturally related Varies among individuals


Pain Pathways

Nociceptors Stimulated by

• Thermal means: extreme temperatures• Chemical: For example, acids or chemicals produced by

body (e.g., bradykinin, histamine, prostaglandin)• Physical: pressure


Pain Fibers

Afferent fibers Myelinated A delta fibers

Transmit impulses very rapidly Acute pain

• Sudden, sharp, localized Unmyelinated C fibers

Transmit impulses slowly Chronic pain

• Diffuse, dull, burning, or aching sensation


Pain Pathways (Cont.)

Dermatome Area of skin innervated by a specific spinal nerve Somatosensory cortex → “mapped”

• Corresponds to source of pain stimuli Reflex response

Involuntary muscle contraction away from pain source

Involuntary muscle contraction to guard against movement



Spinothalamic bundle in the spinal cord Neospinothalamic tract → fast impulses; acute

pain Paleospinothalamic tract → slow impulses;

chronic, dull pain Spinothalamic tracts connect with reticular

formation of brain



Somatic sensory area in the cerebral cortex located in the parietal lobe Perception and localization of sensation

Hypothalamus and limbic system Emotional factors

Communication with other regions of the brain to integrate responses

Reticular activating system (RAS) Reticular formation in the pons and medulla Awareness of incoming brain stimuli


Physiology of Pain and Pain Control

Gate control theory Control systems, “gates” built into normal pain

pathways Can modify pain stimuli conduction and

transmission in the spinal cord and brain Gates open

• Pain impulses transmitted from periphery to brain Gates closed

• Reduces or modifies the passage of pain impulses


Pain Control―Gate Open


Pain Control―Gate Closed


Pain Control

Application of ice Impulses from temperature receptors close gates.

Transcutaneous electrical nerve stimulation (TENS) Increases sensory stimulation at site, blocking

pain transmission Opiate-like chemicals (opioids)

Secreted by interneurons of the CNS (endogenous)

Block conduction of pain impulses to the CNS Resemble morphine

• Enkephalins, dynorphins, beta-lipoproteins


Signs, Symptoms, and Diagnosis of Pain

Location of pain Descriptive terms

Aching, burning, sharp, throbbing, widespread, cramping, constant, periodic, unbearable, moderate

Timing of pain Association with an activity

Physical evidence of pain Pallor and sweating High blood pressure, tachycardia


Signs, Symptoms, and Diagnosis of Pain (Cont.)

Nausea and vomiting May occur with acute pain

Fainting and dizziness May occur with acute pain

Anxiety and fear Frequently evident in people with chest pain or

trauma


Signs, Symptoms, and Diagnosis of Pain (Cont.)

Clenched fists or rigid faces Restlessness or constant motion Guarding area to prevent stimulation of

receptors


Young Children and Pain

Infants respond physiologically Examples: tachycardia, increased blood pressure,

facial expressions Great variations in different developmental

stages: Different coping mechanisms Range of behavior Often have difficulty describing the pain Withdrawal and lack of communication in older

children


Referred Pain

Source may be difficult to determine. Pain may be perceived at site distant from

source Characteristic of visceral damage in the abdominal

organs Heart attack or ischemia in the heart


Location of Referred Pain


Phantom Pain

Usually in adults More common if chronic pain has occurred Can follow an amputation

Pain, itching, tingling Usually does not respond to common pain

therapies May resolve within weeks to months Phenomenon not fully understood


Pain Perception and Response

Pain tolerance Degree of pain, intensity, or duration May be increased by endorphin release May be reduced because of fatigue or stress Varies among people in different situations

Pain perception Subjective but can be compared from day to day

in same person Response to pain

Influenced by personality, emotions, and cultural norms


Acute Pain

Usually sudden and severe, short term Indicates tissue damage May be localized or generalized Initiates physiologic stress response

↑ Blood pressure and heart rate; cool, pale, moist skin; ↑ respiratory rate; ↑ skeletal muscle tension

Vomiting may occur. Strong emotional response may occur.


Chronic Pain

Occurs over extended time; may be recurrent Usually more difficult to treat than acute pain Often perceived to be generalized Individual may be fatigued, irritable,

depressed Sleep disturbances common Specific cause may be less apparent. Appetite may be affected.

Can lead to weight gain or loss


Chronic Pain (Cont.)

Frequently affects daily activities Accommodation and pacing of activities may be

required. Periods of acute pain may accompany

chronic pain conditions. Usually reduces tolerance to additional pain


Comparison of Acute and Chronic Pain


Headache: Types and Causes

Congested sinuses, nasal congestion, eye strain

Muscle spasm and tension From emotional stress

In temporal area Temporomandibular joint syndrome

Migraine Abnormal blood flow and metabolism in the brain

Intracranial headaches Increased pressure inside the skull


Headache: Types and Causes (Cont.)

Central pain Caused by dysfunction or damage to the brain or

spinal cord Neuropathic pain

Caused by trauma or disease involving the peripheral nerves

Ischemic pain Results from a profound, sudden loss of blood flow

to an organ or tissue Cancer-related pain

Caused by advance of the disease; pain associated with treatment; result of coexisting disease


Methods of Managing Pain

Remove cause of pain as soon as possible Use of analgesic medications

Orally Parenterally (injection) Transdermal patch Classified by ability to relieve

• Mild pain• Moderate pain• Severe pain


Analgesic Drugs


Methods of Managing Pain (Cont.)

Sedatives and antianxiety drugs Adjuncts to analgesic therapy Promote rest and relaxation May reduce dosage requirements for analgesic

Chronic and increasing pain May occur in cancer Stepwise fashion to reduce pain Tolerance to narcotics develops over time

• Increase dose requirements• New drug may be required


Methods of Managing Pain (Cont.)

Severe pain Patients administer medication, as needed. Patient-controlled analgesia (PCA) Lessens overall consumption of narcotics

Intractable pain Cannot be controlled with medication Surgical intervention is a choice.

• Rhizotomy• Cordotomy • Injections


Anesthesia

Local anesthesia Injected or applied to skin or mucous membranes

Spinal or regional anesthesia Blocks pain from legs or abdomen

General anesthesia Causes loss of consciousness (gas or injection)

Neuroleptanesthesia Patient can respond to commands. Relatively unaware of procedure, no discomfort


Anesthetics

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