Chapter 18Antimicrobials, Antifungals, and

Antivirals

Common IndicationsCommon Indications

• Infections due to microorganisms, fungi, viruses• Disinfectants, germicidal, antiseptics used in

medical clinical areas

Clostridium perfringens.From Cotran RS, Kumar V, and Collins T (1999): Robbins’ pathologic basis of disease (6th ed). Philadelphia: Saunders.

MicroorganismsMicroorganisms

• Microbiology—study of microscopic organisms– bacteria– viruses– parasites– fungi– protozoa

• Can be pathogenic (disease-causing) or normal flora• Can be identified by shape (i.e., cocci, spirilla), gram

staining (positive or negative), or need for oxygen– aerobic– anaerobic– facultative

AntimicrobialsAntimicrobials

• Destroy microorganisms or inhibit microorganism growth

• Include:– antibiotics—natural or synthetic substance

interfering with microbial growth

– bacteriostatics—inhibit bacterial growth

– bactericidal agents—cause death of bacterial cell

Antibiotic TherapyAntibiotic Therapy

• Choose carefully based on sensitivity of infecting organism

• Rarely given preventatively or prophylactically except in cases of surgery or exposure to unusual disease

• Narrow-spectrum antibiotics effective against only a few microorganisms

• Broad-spectrum antibiotics effective against wide range of microbes

Antibiotic TherapyAntibiotic Therapy

• Prescribed only when indicated by a specific disease

• Fever only a symptom and not reason to begin therapy

• Antibiotics ineffective for treatment of viral infections

• Take entire prescribed course• Disappearance of symptoms does not indicate

infection is gone

PenicillinsPenicillins

• Weaken cell walls causing lysis and death• Gram-negative bacteria resistant to most

penicillins• Safest antibiotic available; but patient allergic to

one penicillin considered allergic to all penicillins• Principal differences among penicillins—

spectrum of antibacterial action, stability in stomach acids, duration of action

• Effectiveness of birth control pills decreases when certain penicillins used concurrently

CephalosporinsCephalosporins

• Weaken cell walls, causing death to bacteria• Closely related to penicillins• Grouped into 4 generations; each one has

increased activity against gram-negative bacteria

• Many given parenterally• If oral, take with food if gastric upset occurs

CephalosporinsCephalosporins

• Carefully watch patients allergic to penicillins when administering cephalosporins

• Refrigerate suspensions• Some cannot be combined with alcohol• Cephalosporins intensify bleeding tendencies• Many names contain -cef or -ceph in

brand/generic name

MacrolidesMacrolides

• Broad-spectrum antimicrobials• Names of drugs usually end in –mycin• Take erythromycin and chloramphenicol on

empty stomach; may be taken with meals if GI upset occurs

• Erythromycin generally safe; given to patients with penicillin allergies

Common MacrolidesCommon Macrolides

• erythromycin• EES• Zithromax• Biaxin• Dynabac• TAO

TetracyclineTetracycline

• First group of broad-spectrum antibiotics• Adverse reactions—photosensitivity, staining of

developing teeth• Do not give with calcium supplements, milk

products, iron supplements, magnesium-containing laxatives, most antacids

• Names of drugs usually end in -cycline

AminoglycosidesAminoglycosides

• Potent bactericidal agents usually reserved for serious or life-threatening infections

• Nephrotoxic and ototoxic• Have patients report dizziness, tinnitus,

unsteadiness, hearing loss, oliguria• Topical use relatively safe

Common AminoglycosidesCommon Aminoglycosides

• amikacin• gentamicin• kanamycin• neomycin• streptomycin• tobramycin

Quinolone AntimicrobialsQuinolone Antimicrobials

• Broad-spectrum antibiotics with mild side effects• Do not take ciprofloxin with milk products,

antacids, iron supplements, magnesium laxatives

• Do not give ciprofloxin to children younger than 16–18 years (cartilage damage)

Common Quinolone AntimicrobialsCommon Quinolone Antimicrobials

• Cipro• Penetrex• Maxaquin• Levaquin• Noroxin• Floxin• Tequin• Avelox

Miscellaneous AntibioticsMiscellaneous Antibiotics

• Vancomycin—toxic; reserved for treating serious infections in patients allergic to penicillin

• Chloramphenicol—cause serious blood dyscrasias

• Metronidazole (Flagyl)—used against protozoa, anaerobic bacteria

• Topical antibiotic preparations usually contain neomycin, bacitracin, polymyxin B

Sulfonamides (Sulfa Drugs)Sulfonamides (Sulfa Drugs)

• Antibacterials slow growth of bacteria while body builds its own defenses

• Primarily treat urinary tract infections, in combination therapy for otitis media

• Take oral sulfonamides with full glass of water on empty stomach

Sulfonamides (Sulfa Drugs)Sulfonamides (Sulfa Drugs)

• May cause photosensitivity reactions• Urine should be acidic for optimum

effectiveness• Take medications for urinary tract infections

for 2 weeks to prevent development of more resistant infections

• Topical preparations available in ocular forms, lotions, powders, ointments

Common Sulfonamides(Sulfa Drugs)Common Sulfonamides(Sulfa Drugs)

• Gantrisin• Gantanol• Azulfidine• Triple Sulfa• Bactrim• Septra• Sulamyd• Silvadene cream

Urinary Tract AntisepticsUrinary Tract Antiseptics

• Agents reduce microbial flora by inhibiting growth

• Do not achieve effective antibacterial concentration in blood or tissue

• Usually second choice of drugs after antibiotics or sulfonamides

• Include nitrofurantoin, methenamine, nalidixic acid, cinoxacin

Fungal InfectionsFungal Infections

• Fungi include spore-forming yeasts and molds thriving on dead plants and animals

• Fungi produce irritating symptoms; normally controlled by bacteria, immune system

• Fungi prefer moist, warm, dark environment (feet, crotch, underarm areas)

Fungal InfectionsFungal Infections

• Many are opportunistic infections (because immune system cannot fight normal flora)

• Long-term antibiotic or radiation therapy can create conducive environment

• Most common fungal infections:– ringworm

– athlete’s foot

– Candida albicans in mouth, vagina

Drugs to Treat Fungal InfectionsDrugs to Treat Fungal Infections

• Systemic and topical• Fungicidal (kill fungi) or fungistatic (inhibit fungal

growth)• Most topical medications available OTC• Antifungals designed to be used for 4 weeks

(unless used on nails)

Common Antifungal DrugsCommon Antifungal Drugs

• Fungizone• Diflucan• Nizoral• Mycostatin• Lamisil• Lotrimin• Monistat• Terazol• Desenex

Viral InfectionsViral Infections

• Viruses—strands of genetic material wrapped in protein

• Cannot sustain themselves independently; must rely on host

• Difficult to suppress viral reproduction; host’s body cells would be harmed also

Drugs to Treat Viral InfectionsDrugs to Treat Viral Infections

• Drugs decrease symptoms, do not cure• Resistance to antiviral drugs major problem• Drug classifications:

– non-HIV infection medications

– HIV infection medications

Common Non-HIV Antiviral DrugsCommon Non-HIV Antiviral Drugs

• Symmetrel and Flumadine—Influenza A

• acyclovir (Zovirax)—herpes simplex, genital herpes, varicella zoster infections

• ganciclovir— cytomegalovirus

HIV AntiviralsHIV Antivirals

• No cure for HIV• Dramatic advances in drug therapy• Health preserved, life prolonged• Multiple drug interactions and side effects• High cost, toxicity• Drug cocktail used; patient must adhere closely

to prescribed dosage schedules• New drugs prescribed should be agents the

patient has never taken

Antiseptic vs. DisinfectantAntiseptic vs. Disinfectant

• Antiseptic—agent reducing, preventing, or inhibiting growth of microbial flora of skin and mucous membranes without necessarily killing them

• Disinfectant (germicide)—agent decreasing number of microorganisms on inanimate objects by killing bacteria

• Sanitization—process of cleaning and removing dirt