Antibiotics, Antivirals

Barbara S. Hays, RNWinter 2006

Principles of antimicrobial therapy

• Bactericidal agents: kill organisms

• Bacteriostatic agents: inhibit growth, usually by inhibiting protein synthesis

Antimicrobial therapymechanisms of action

• Inhibition of cell wall synthesis– Penicillins, Cephalosporins

• Organism becomes osmotically unstable: lysis

• Inhibition of protein synthesis– Aminoglycosides

• Cause formation of abnormal proteins/inhibit synthesis by irreversible binding to ribosomal subunit

• Disruption/alteration of membrane permeability– Antifungals

• Bind to specific cell wall components• Organism leaks cellular components

Antimicrobial therapymechanisms of action, II

• Inhibition of nucleic acid synthesis (RNA/DNA)– Antivirals

• Inhibition of specific biochemical pathways– Bacteriostatic agents– Competitively inhibit metabolic pathways

that are critical to survival of the organism

Selection of antibiotics

• Sometimes broad spectrum antibiotics before Culture/Sensitivity (“C&S) results

• Once results in: change to least toxic antibiotic to which organism is sensitive

• Gram stain– Positive (holds purple stain)

• Also see if cocci, rods, etc

– Negative (takes red counterstain)

Selection of antibiotics

• Combination therapy– When synergistic effect desired– When development of resistance is a

problem, like with TB– When nature of infection is not known

[or multiple, mixed organisms]

Administration of antibiotics

• Oral– Unpleasant taste– GI upset– Client may stop taking when begins to feel

better – relapse and resistance a concern

• Intramuscular– Painful/irritating (may mix with lidocaine)– Rotate injection sites– Avoid in shock/hypoperfusion states– [vancomycin IM causes tissue necrosis]

Administration of antibiotics

• Intravenous (requires the most nsg care)– When high concentrations must reach site– When client unable to take oral meds, or if oral

absorption is poor– When antibiotic of choice is only available in

this form

• Nursing implications– Accurate/timely administration is a must

• Inadequate response• Development of resistant organisms

– Drug imcompatibilities– Phlebitis

General side/adverse effects of antimibrobials

• Allergic reactions– Generalized rash to life-threatening

anaphylactic shock• Rashes: mild – antihistamines (or tolerate it)• Anaphylactic reactions

– Hypotension– Cardiovascular collapse– Bronchoconstriction– Laryngospasm

General side/adverse effects of antimibrobials

• Superinfections/opportunistic infections– Normal flora altered

• Buttermilk, live cultured yogurt

– Some resistant to current antibiotic flourish

• Other– Fluid/electrolyte (many are sodium salts)

• Fluid retention, CHF

– GI upsets (n/v/d)

Antibiotic use during pregnancy

• All antimicrobials cross placenta to some degree. May be teratogenic (not much literature, so physicians are careful)

• Tetracyclines– Disrupt tooth/bone formation in fetus

Antibiotic use in children and the elderly

• Children– Absorption, distribution, metabolism and

excretion issues– Elimination dependent on health of kidneys – Immature liver of neonate may be unable to

inactivate the medication

• Elderly– Similar to very young because of diminished

functions

Aminoglycosides(“Easy” p 473)

• Gentamycin/Garamycin prototype (p 474)– Bactericidal against gram negative, gram

positive, myocbacteria [TB, Leprosy], and protozoans

– Poorly absorbed [“gut active”, esp. neomycin] so given IV or IM

– Penicillin assists to transport across cell membrane

– Toxic (so peak/trough levels)• Kidneys (if doesn’t drop below 2mcg/ml) – keep well

hydrated and watch BUN/creatinine levels• Nerves• 8th cranial nerve: hearing (if rises above 12 mcg/ml)• Allergic reactions, anaphylaxsis• agranulocytosis

Penicillins (“Easy” p 477)

• Natural penicillins (Prototype p 479). Mold.– About all there was during WWII

• Then most staph was susceptible to PCN.• Now over 90% of the strains are resistant to PCN.

• Penicillinase• Penicillinase-resistant penicillins

– Methcillin, Staphcillin, Unapen– [MRSA – can live on your hands for three hours]

• Aminopenicillins– Ampicillin, Unasyn (may cause nephritis,

agranulocytosis)

• Extended spectrum penicillins– Ticarcillin, Pipercillin

Penicillins (“Easy” p 479, 480)

• Drug interactions– Probenecid increases plasma

concentration by competing for excretion by kidneys

– Decreased effectiveness of hormonal contraceptives

– Large doses can cause bleeding– High doses inactivate aminoglycosides

(while lower doses help…)

Penicillins (“Easy” p 480)

• Adverse reactions– Hypersensitivity

• Rash to anaphylactic shock

– GI upset• Tongue inflammation (stomatitis, glossitis)• n/v/d

– Liver toxicity by Oxacillin

Cephalosporins (“Easy” p 482)

• Derived from fungus, structurally similar to PCNs

• Divided into “generations” based on spectrums of activity, typically broader with each generation– First generation– Second generation– Third generation– Fourth generation

Cephalosporins

• Things to consider (p 486)– Antabuse-like reaction up to 72 hours

after dose

– Increased risk of bleeding with some

– Risk of cross-allergy to those sensitive to PCNs

Tetracyclines (“Easy” p 489)

• Prototype: p 490– Tetracycline HCl (Achromycin)– Vibramycin– Aureomycin

• Work well for acne, respiratory infections, syphilis (but bacteria may become resistant)

• Absorption reduced with milk, antacids, calcium

Tetracyclines

• Adverse reactions (p 491)– Superinfection– GI upset

• Stomatitis, “black hairy tongue”• n/v/d

– Photosensitivity– Hepatic toxicity– Renal toxicity– Affects forming teeth/bones

Macrolides (“Easy” p 495)

• Erythromycin– Acid sensitive (so need enteric coating)– Cross BBB only with inflammation– Effective for those with PCN allergy– Use for Chlamydia [Ilotycin for

neonates]

• Adverse effects (see p 497)

Vancomycin (“Easy” p 498)

• Used for treating MRSA– Adverse reactions (p 499)

• Hypersensitivity/anaphylaxsis• “red man syndrome”• Neutropenia• Hearing loss (temporary/permanent)

• VRE’s… [can live on surfaces for weeks!]

Fluoroquinolones [“quinolones”](“Easy” p 507)

• Used frequently in urinary tract infections• Synthetic, broad spectrum• Slow microbial resistance• Food/dairy products reduce absorption• Family members

– Cipro (ciprofloxacin)– Levaquin (levofloxacin)– [NegGram (naladixic acid)] – Floxin (ofloxacin)

Fluoroquinolones [“quinolones”]

• Interact with many medications• GI upset• Compete with probenecid for

excretion in the kidneys• (go over client teaching p 509)

Sulfonamides (“Easy” p 510)

• Prototype pro p 511 [Septra/Bactrim]• Used for UTIs, ear infection, newborn

eye prophylaxsis• Give on empty stomach with full

glass of water– Cause crystalluria and subsequent stone

formation (client to drink 2-3 quarts/day)

Sulfonamides

• Adverse reactions (p 511)– Urine crystals– Hypersensitivity/allergy– Increased effects of oral hypoglycemic

agents

Antitubercular (“Easy” p 540 – 545)

• Tuberculosis: on the rise again…– Droplet spread– Already tough to treat, is becoming more and more

resistant

• Currently recommending 4-fold attack (p 540). Bring out the big guns. In combination.– Isoniazid (INH)– Rifampin [also used for severe, resistant infections]– Pyrazinamide– Streptomycin or ethambutol

• Client non-compliance– Long term therapy, expense (6-9-12 months)– “DOT” therapy (directly observe client taking the med)

Antitubercular meds

• Side effects/adverse effects to consider– INH

• Peripheral neuropathy• hepatotoxicity

– INH and Ethambutol• Visual disturbances

– Streptomycin• Ears• kidneys

Antifungal drugs (“Easy” p 545)

• Go over p 546 and put in names– Clotrimazole (GYNe-Lotrimin, Mycelex)– Grisofulvin (Fulvicin)– Miconazole (Monistat)

Polyenes (“Easy” p 545)

– Amphoteracin B [“ampho-terrible B” and Diflucan p 554]

– Nystatin (Mycostatin) -- topical

– (esp. Amphoteracin B) – drug interactions (p 547)• Serious interactions with many drugs• Kidney toxicity• Produces hypokalemia (as do steroids and

extended release PCNs. Watch for digitalis toxicity!)

Diflucan (p 554)

• Much like amphoteracin B

• Drug interactions (p 555)

Antivirals (“Easy” p 516 – 539)

• Acyclovir/Zovirax (prototype pro p 517)– Disrupts viral replication

• Used to treat – genital herpes, simplex II– Shingles (chickenpox virus)– CytoMegal Virus (CMV) in those

immunocompromized with AIDS

• Adverse reactions (p 518)

Antivirals

• [Relenza (zanamvir)]– Funky powder to inhale– Does not permit release of newly formed

viruses from surface of infected cells– Works for flu A and B

Antivirals

• Ribavirin (“Easy” p 522 – 526– Inhaled gives high concentrations in

lungs– Good for children with RSV

(of course you remember about children, viral illnesses, ASA, and Reye’s Syndrome…)

Antivirals to treat advanced HIV

• Retrovir (AZT) to treat AIDS– IV to prevent transmission to fetus

• Combination therapy works best

• Go over adverse reactions p 531

• Teaching (go over p 531)