2© Paradigm Publishing, Inc. Chapter 3 The Immune System and Drugs for Infectious Diseases.

© Paradigm Publishing, Inc. 2

Chapter 3

The Immune System and Drugs for Infectious Diseases


Chapter 3

Topics

• Anatomy and Physiology of the Immune System• Bacterial Infections• Viral Infections• Fungal Infections• Parasitic and Protozoan Infections• Herbal and Alternative Therapies


Anatomy and Physiology of the Immune System

The Immune System• Body’s built-in defense mechanism against pathogens• Works in two ways

Local level is called nonspecific immunity Also known as the innate response or

inflammation Systemic level is called acquired immunity



Nonspecific Immunity• Is a local response that occurs at a wound site • Involves an increase in WBCs, blood flow, and fluids• Causes inflammation, redness, and swelling• Results in the destruction of bacteria and the repair of

tissue



Acquired Immunity• Is a systemic response that occurs when pathogens enter

the bloodstream• Involves leukocytes (white blood cells, or WBCs) and

lymphocytes (T cells and B cells)



Acquired Immunity (continued)• Killer T cells attack cells

infected with viruses• Helper T cells stimulate B

cells to make antibodies• B cells provide humoral

immunity by making antibodies

• Antibodies remember viruses in case the body encounters them again



The Lymphatic System• Set of vessels that filter lymph, the fluid that has leaked

out of the bloodstream into tissue spaces• Fluid is filtered through lymph nodes and then returns to

the bloodstream• WBCs often detect and destroy pathogens in the lymph

nodes• In this way, the immune system and the lymphatic system

work together


Bacterial Infections

Bacteria• Single-celled microorganisms that live everywhere• Aerobic (need oxygen) or anaerobic (do not need oxygen)• Classified by shape

Spherical bacteria (a) are cocci Rod-shaped bacteria (b) are bacilli Spiral-shaped bacteria (c) are spirochetes



Bacteria (continued)• Also classified by arrangement of growth

Strep grows in chains or lines Staph grows in clusters Diplo grows in pairs

• Gram-positive (thick cell wall) or gram-negative (thin cell wall)



Drugs for Bacterial Infections• Antibiotics are used to treat bacterial infections

Bacteriostatic antibiotics hinder growth of bacteria Bacteriocidal antibiotics kill bacteria

• Antibiotics are chosen by type, site, and severity of infection

• Antibiotic resistance is a growing problem • Antibiotics are best given at intervals during the day



Common Classes of Antibiotics• Penicillins• Cephalosporins • Carbapenems and Monobactams• Vancomycin • Macrolides• Aminoglycosides• Tetracyclines• Fluoroquinolones• Sulfonamides and Nitrofurantoin• Metronidazole



Penicillins• Kill bacteria by preventing formation of cell wall• Indications: respiratory, tooth/gum, ear, skin infections,

strep throat, syphilis, gonorrhea, and endocarditis• Cautions: work best on empty stomach

Take with food if stomach upset Do not take with fruit juice or cola due to drug

deactivation• Side Effects: stomach upset and diarrhea; allergies in 10%

of patients• Routes: many are oral; some are IM or IV



Cephalosporins• Kill bacteria by preventing formation of cell wall• Divided into four groups called generations

First-generation works best on gram-positive bacteria Increased activity against gram-negative bacteria as you

move up through generations• Indications (general): upper and lower RTIs, skin infections,

infection prophylaxis during surgery, and difficult infections• Indications (second-generation): respiratory infections

caused by Haemophilus influenzae and otitis media



Cephalosporins (continued)• Indications (third-generation): severe gram-negative

infections• Indications (fourth-generation): Pseudomonas infections• Cautions: to work properly, some are taken with food and

others are taken on an empty stomach Take cefditoren with food Do not take cephalosporins with antacids or alcohol

• Side Effects: nausea, vomiting, diarrhea, headache, dizziness, and allergies in 10% of penicillin-allergic patients

• Routes: many are oral; some are IM or IV



Carbapenems and Monobactams• Kill bacteria by preventing formation of cell wall• Indications (both drug classes): serious nosocomial

infections• Indications (monobactams): gram-negative bacterial

infections Aztreonam

• Indications (carbapenems): mixed infections that have both gram-positive and gram-negative bacteria Ertapenem, imipenem, and meropenem



Vancomycin(Vancocin)• Kills bacteria by preventing formation of cell wall• Indications: gram-positive bacteria and mainly MRSA

infections Some enterococci resistant to vancomycin; called VRE

• Routes: mostly used in IV form Administer slowly to avoid red man syndrome Display infusion rates prominently on IV bag label

• Side Effects (severe): nephrotoxicity (kidney damage) and ototoxicity (hearing loss)



Macrolides• Kill bacteria by preventing production of essential proteins • Erythromycin is the most commonly used macrolide• Indications: broad spectrum of activity; some gram-

positive and gram-negative bacteria Mainly used for respiratory infections and pneumonia Also used with other drugs to treat Helicobacter pylori,

the bacteria found in stomach ulcersAzithromycin has 3–5 days of therapyOther macrolides usually have 7–14 days of therapy



Macrolides• Side Effects: stomach upset, nausea, vomiting, heartburn,

abdominal pain, and diarrhea Take with food Erythromycin can cause liver toxicity and jaundice

• Cautions: many drug interactions, especially erythromycin; some effects are serious

• Routes: all are oral; some are IM or IV Routes for erythromycin include many types of oral

dosage; also available in IM, IV, or topical



Aminoglycosides• Kill bacteria by preventing production of essential proteins • Indications: powerful bacteriocidal for peritonitis, severe

gum infections, and life-threatening infections such as sepsis Often used with other antibiotics; work synergistically

• Pulse dosing: given once a day (not multiple times a day)• Caution: can cause neuromuscular blockade

Discontinue drug if muscular weakness, breathing difficulty, numbness, and convulsions occur

• Caution: not for use in patients with muscular disorders • Routes: all are IM, IV; some are ophthalmic or inhaled



Tetracyclines• Kill bacteria by blocking protein synthesis• Indications (for the drug class): Lyme disease and Rocky

Mountain spotted fever• Indications (for the generic drug itself): acne• Indications (for doxycycline): sexually transmitted diseases• Side Effects: stomach upset, nausea,

vomiting, and photosensitivity Do not take with dairy or antacids

• Children under eight and pregnant women should not take• Routes: all are oral; some are IV



Fluoroquinolones (Quinolones)• Kill bacteria by preventing production of DNA• Indications: strong activity against gram-negative bacteria;

used for bone, joint, and eye infections; RTIs; UTIs Also used for anthrax and potential bioterrorism agent

• Resistance has developed; only used for serious infections• Side Effects: nausea, vomiting, dizziness, diarrhea, and

photosensitivity Do not take with dairy, antacids, or juices with calcium Ciprofloxacin can cause mental function changes

• Routes: most are oral; some IV; gatifloxacin is ophthalmic



Sulfonamides (Sulfa Drugs) and Nitrofurantoin • Kill bacteria by preventing production of folic acid• Indication: UTIs

Most common sulfa drug is a combination containing trimethoprim; used for UTIs caused by Escherichia coli

• Side Effects (sulfa drugs): nausea, vomiting, fever, photosensitivity, and sulfa allergy Rarely, jaundice and Stevens-Johnson

syndrome occur• Side Effects (nitrofurantoin): nausea and vomiting

Turns urine brown • Routes: all are oral; some are IV



Metronidazole • Structured like antifungal drug but works like an antibiotic

Also has activity on some protozoa• Indications: Giardia, amebic dysentery, bacterial vaginosis,

trichomoniasis, rosacea, and H. pylori ulcers• Side Effects: headache, anorexia, vomiting, diarrhea, and

abdominal cramps Take with food to help lessen side effects Do not take with alcohol; can cause severe reaction

• Routes: oral, topical, vaginal, and injectable


Your Turn

Question 1: A patient purchased an antibiotic that had a length of therapy of fourteen days. The bacterial infection returned. What could have caused this to happen?

Answer: The patient may not have taken the full course of drug therapy. Most antibiotics are taken for 10–14 days.

Question 2: What restriction applies to cephalosporins, sulfa drugs, and metronidazole?

Answer: Patients taking these drugs should not consumeany alcohol.


Viral Infections

Viruses• Are segments of nuclear material (DNA or RNA)

surrounded by a capsule or protein coating• Mechanism of Action: attach to human cells

Inject their nucleic material Cause normal cells to die, releasing new viruses

• HIV virus causes AIDS• Common viruses are influenza and herpes (chicken pox,

shingles, sexually transmitted diseases)• Other common viruses include hepatitis, measles, mumps,

rubella, West Nile, rabies, RSV, and rotavirus


Viral Infections

Drugs for Viral Infections• Antivirals are used to treat viral infections• Antivirals prevent viruses from entering cells or alter the

ability of viruses to replicate• Best to prevent viral infections by using vaccines when

possible• Antivirals do not cure common infections, such as influenza,

cold sores, and shingles, but limit viral replication• Side Effects (common antivirals): headache, malaise,

fatigue, nausea, vomiting, diarrhea, cough, and rash• Routes (common antivirals): all are oral; also topical or IV


Viral Infections

Drugs for Viral Infections: HIV and AIDS• Many antivirals are used to treat HIV and AIDS• Side Effects: severe and numerous; many drug interactions• Drugs for HIV and AIDS are combined into a therapy, called

a cocktail This synergistic drug therapy attacks viral replication in

multiple stages• Drugs are taken throughout life to prevent progression of

the illness and death• Drug instructions must be strictly followed


Viral Infections

Nucleoside and Nucleotide ReverseTranscriptase Inhibitors (NRTIs, NtRTIs)• Mechanism of Action: HIV agents that inhibit reverse

transcriptase from forming pro-DNA inside of T cells• Side Effects: nausea and vomiting that can be severe• Side Effects (severe): lactic acidosis, pancreatitis, and

peripheral neuropathy• Cautions: Do not take with alcohol;

these agents have many drug interactions• Routes: all are oral; zidovudine is also IV


Viral Infections

Non-nucleoside Reverse Transcriptase Inhibitors (NNRTIs) • Mechanism of Action: HIV agents that inhibit reverse

transcriptase from forming pro-DNA inside of T cells• Cautions:

Efavirenz should not be taken with high-fat meals Delavirdine should not be taken with antacids

• Routes: all are oral


Viral Infections

Protease Inhibitors (PIs) • Mechanism of Action: HIV agents that block the enzyme

that affects the assembly of proteins into working HIVs• Side Effects: diarrhea, headache, fatigue, dizziness, nausea,

vomiting, bleeding problems, pancreatitis, depression, and Stevens-Johnson syndrome

• Side Effects (severe): development of allergic reactions, diabetes, and liver and/or kidney problems

• Cautions: many drug interactions; do not use with antihistamines

• Routes: all are oral


Viral Infections

Miscellaneous New Therapies • Fusion inhibitor: enfuvirtide (Fuzeon)

Mechanism of Action: blocks HIV from attaching to cellular membranes

It is costly; used for advanced AIDS Side Effects: diarrhea, nausea, fatigue, and injection site

irritation Routes: SC injection


Viral Infections

Miscellaneous New Therapies (continued)• Chemokine coreceptor (CCR5) inhibitor: maraviroc

(Selzentry) Mechanism of Action: blocks HIV from attaching to cells Side Effects: abdominal pain, cough, dizziness, and fever Side Effects (severe): allergic reactions and hepatotoxicity

• Integrase inhibitor: raltegravir (Isentress) Mechanism of Action: prevents HIV from inserting into

host DNA Routes: oral; in combination with other antivirals Side Effects: headache, nausea, and fatigue


Fungal Infections

Fungi• Yeasts and molds that are one-celled plant organisms• Plant-like cell wall (the target for most antifungals)• Fungal infections are usually topical and mild• Dermatophytes are common fungi of skin

Cause frequent infections such as athlete’s foot and ringworm

• Candidiasis is common fungus that causes vaginal yeast infections and oral thrush

• If fungus enters bloodstream or cannot be destroyed it can cause serious systemic infections


Fungal Infections

Drugs for Fungal Infections• Most kill fungi by causing cells walls to form improperly

They work on ergosterol in the cell wall of fungi• Many fungal infections and treatments are topical • Oral or IV forms are used for systemic fungal infections

Toxic to liver when given systemically; use pulse dosing Amphotericin B very toxic to liver and kidneys

IV liposome form surrounds drug with fat/oil layer; decreases direct contact to body tissues

Routes (common fungi): topical, oral, IV, vaginal


Parasitic and Protozoan Infections

Parasites and Protozoa• Parasites are organisms that live off of a host (do not kill

host) Cause great discomfort and severe symptoms Pinworms, hookworms, roundworms, and tapeworms

• Protozoa is a single-celled parasites that cause infection Usually transmitted through the oral–fecal route Giardia is an intestinal infection causes diarrhea Sporozoan infection malaria affects millions of people

Drugs for Parasitic and Protozoan Infections• Metronidazole is used for common intestinal infections


Herbal and Alternative Therapies

• Echinacea is an herb for common cold, RTIs, and vaginal yeast infections Reduces severity and length of symptoms

• Zinc is a cofactor in many body processes Boosts immune function Taken for common cold, flu, and RTIs Do not take with coffee; prescription drugs interactions

• Vitamin C is an ascorbic acid Boosts immune system Antioxidant effects Taken for common cold and flu


Your Turn

Question 1: What is the purpose of liposomal amphotericin? Answer: The liposome layer that surrounds amphotericin protects body tissues from coming into direct contact with the drug. This reduces the toxic effects of the drug.

Question 2: How are fusion inhibitors and chemokine coreceptor (CCR5) inhibitors different from other HIV agents?

Answer: They prevent the HIV virus from entering T cells. Other agents alter the ability of the HIV virus to replicate.


Summary• Infections are caused by pathogenic organisms• Organisms that cause disease are bacteria, viruses, fungi,

parasites, and protozoa• Bacterial infections are treated with antibiotics• Viral diseases are treated with antiviral agents• Fungal infections are treated with antifungal drugs

2© Paradigm Publishing, Inc. Chapter 3 The Immune System and Drugs for Infectious Diseases.

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Transcript of 2© Paradigm Publishing, Inc. Chapter 3 The Immune System and Drugs for Infectious Diseases.