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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 (6th 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, magnesiumcontaining 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