Chapter 18 Antimicrobials, Antifungals, and Antivirals

Common 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 (6 th ed). Philadelphia: Saunders.

Microorganisms 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

Antimicrobials 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 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 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

Penicillins 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

Cephalosporins 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

Cephalosporins 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

Macrolides 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 Macrolides erythromycin EES Zithromax Biaxin Dynabac TAO

Tetracycline 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

Aminoglycosides 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 Aminoglycosides amikacin gentamicin kanamycin neomycin streptomycin tobramycin

Quinolone 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 Antimicrobials Cipro Penetrex Maxaquin Levaquin Noroxin Floxin Tequin Avelox

Miscellaneous 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) 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) 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) Gantrisin Gantanol Azulfidine Triple Sulfa Bactrim Septra Sulamyd Silvadene cream

Urinary 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 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 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 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 Drugs Fungizone Diflucan Nizoral Mycostatin Lamisil Lotrimin Monistat Terazol Desenex

Viral 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 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 Drugs Symmetrel and Flumadine—Influenza A acyclovir (Zovirax)— herpes simplex, genital herpes, varicella zoster infections ganciclovir— cytomegalovirus

HIV 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. 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