Pharmacology - Antimicrobial Drugs

What is an Infection?

• Occurs when pathogens invade causing harm or disease.

• Immune system is overwhelmed.

• Bacteria, viruses, fungi, parasites.

Antimicrobial Therapy

• Use of medications to treat infections due to bacteria, viruses, fungi.

• Use selective toxicity to kill or otherwise control microbes without destroying host cells.

Why Antimicrobials Matter

• Commonly prescribed

• High-risk if used incorrectly

• Nursing priority: safety and education

• 3 things to remember:

  • Allergy? If yes, what is it? Is it a side effect or and allergy reaction?

  • Opportunistic Infection (Super Infection) - Yeast infections, oral thrush

  • Organ Toxicity - Liver and kidney (possibly ears)!!!

How Antibacterials Work

• Destroying cell wall that is present in bacteria.

• Inhibiting conversion of enzyme unique for a particular bacterium’s survival.

• Impairing protein synthesis in bacteria’s ribosomes

• Disrupting bacterial synthesis or function of DNA and RNA

• Inhibiting metabolic pathways.

Classification of Antibacterial Medication

• Defining which microbes are susceptible to each medication.

  • Narrow-spectrum antibodies

• Identifying the mechanism of action of each antibacterial medication.

  • Bactericidal - I’m killing that bacteria in the pt.

  • Bacteriostatic - I am slowing or stopping the growth of bacteria to stop it from replicating.

Selecting Antibodies

• Identity of causative agent

• Sensitivity of infecting organism to antimicrobial

• Other factors (location of infection, age, allergies, immune status)

Culture and Sensitivity

• Identifies organism

• Laboratory testing of bodily fluids (blood, urine, sputum, and wound drainage)

• Targeted therapy

• May take days

Antibiotic Resistance

• Bacteria adapt and survive (skipped doses and incomplete therapy)

• Misuse allows resistance

• Nurses reduce risk

Superinfections

• Normal microbiome destroyed

• Opportunistic infections

• Examples of signs/symptoms: diarrhea, thrush, vaginitis

Antibiotics Affecting Bacterial Cell Wall

• Penicillins (Penicillin G potassium)

  • Beta-lactamase inhibitors: amoxicillin-clavulanic acid (Augmentin)

• Cephalosporins (Cephalexin, first generation)

• Vancomycin

• Pharmacological action

  • Destroy the bacterial cell walls causing destruction of microorganisms.

Penicillin Complication

• Allergies, anaphylaxis

• Renal impairment

• Hyperkalemia, dysrhythmias, hypernatremia

• At risk for superinfection, GI distress, C. diff

• Interaction: PCN in the same IV solution as aminoglycosides inactivates the aminoglycoside

Nursing Administration: Penicillin

• Instruct patients to report any findings of an allergic response

• Assess for allergy to PCN or cephalosporins

• Complete the entire course of therapy, even if manifestations resolve

• Use an additional contraceptive method

• C&S sample taken before starting antibiotic to identify infective microorganism.

Cephalosporins

• Multiple Generation

  • First Generation - Cefazolin

  • Second Generation - Cefaclor

  • Third Generation - Ceftriaxone

  • Fourth Generation - Cefepime

  • Fifth Generation - Ceftaroline

• Broad-spectrum with a high therapeutic index that treat a wide variety of infections

Cephalosporin Complications

• Allergies, hypersensitivity, anaphylaxis, possible cross-sensitivity to penicillin

• GI distress

• Bleeding tendencies

• Thrombophlebitis with IV infusion

• Renal insufficiency

• Pain with IM injection

• Antibiotic-associated pseudomembranous colitis (caused by Clostridioides difficile)

Nursing Administration: Cephalosporins

• Complete the entire course of therapy even if manifestations resolve

• Take PO with food

• Store PO suspensions in a refrigerator

• Interactions

  • Disulfiram reaction (intolerance to alcohol) when alcohol and cephalosporins are taken concurrently.

Vancomycin

• Commonly used in hospitals

• Poor absorption through GI tract

• Treats infections due to methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, and streptococcal infection

• Treat antibiotic-associated pseudomembranous colitis due to Clostridium difficile

Vancomycin Complication

• Ototoxicity (rare and reversible)

• Infusion reactions (red man syndrome - related to rapid infusions) IM and IV injection-site pain

• Renal toxicity

• Neutropenia (rare and reversible)

Nursing Administration - Vancomycin

• Monitor vancomycin trough levels routinely after steady state reached

• Administer slowly to avoid transfusion reaction

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Antibiotics Affecting Protein Synthesis

• Macrolides (Prototype: Erythromycin)

  • Exemplars: Azithromycin

• Tetracyclines (Prototype: Tetracycline)

  • Exemplars: Doxycycline, Minocycline

• Aminoglycosides (Prototype: Gentamicin)

  • Exemplars: Tobramycin, Neomycin, Streptomycin

Macrolide Complications

• GI discomfort (nausea, vomiting, epigastric pain)

• Prolonged QT intervals

• Ototoxicity with high-dose therapy

Interactions - Macrolides

• Erythromycin inhibits metabolism of:

  • Antihistamines

  • Theophylline

  • Carbamazepine

  • Warfarin

  • Digoxin

• Metabolism of erythromycin is inhibited by:

  • Verapamil

  • Diltiazem

  • Antifungals

  • Nefazodone

Nursing Administration - Macrolides

• If given to treat STD, abstain from intercourse until they finish their medication and manifestations resolve or partners have been treated.

• Hormonal contraceptive effectiveness decreased with various antibiotics.

• Administer oral preparations on an empty stomach, with 8oz of water, unless GI upset occurs.

Tetracycline Complications

• Gi discomfort (including esophageal ulceration)

• Yellow or brown tooth discoloration, hypoplasia of tooth enamel

• Hepatotoxicity

• Photosensitivity

• Superinfection

Interactions - Tetracyclines

• Absorption of tetracyclines reduced with:

  • Milk products

  • Calcium and iron supplements

  • Laxatives containing magnesium

  • Antacids

• Doxycycline increased risk of digoxin toxicity

Nursing Administration - Tetracyclines

• Take tetracyclines on an empty stomach with 8 oz of water (may be taken with food if GI distress occurs)

• Do not take lying down (increased risk of esophageal ulceration)

• Administer at least 1 hr before or 2 hrs after chelating agents

• Complete entire course of therapy; use additional contraception

Aminoglycosides - Complications

• Ototoxicity

• Nephrotoxicity

• Intense neuromuscular blockade (results in respiratory distress, muscle weakness)

• Hypersensitivity

Interactions - Aminoglycosides

• Penicillin inactivates aminoglycosides when in the same IV solution.

• Concurrent administration with other ototoxic drugs increases risk for ototoxicity

• Concurrent administration with skeletal muscle relaxants increases risk for neuromuscular blockade

Nursing Administration - Aminoglycosides

• Most are parenteral

  • Neomycin also has oral and topical formulations

  • Tobramycin also has inhalation formulation

• Base acquisition of aminoglycoside level on dosing schedules

  • Once-a-day dosing (blood sample only necessary for measuring trough levels)

  • Divided doses

    • Peak: 30 mins after IM; 30 min after completion of IV

    • Trough: right before next dose

Fluoroquinolones (Prototype: Ciprofloxacin)

• Exemplars: Levofloxacin, Ofloxacin

• Action: Inhibition of an enzyme necessary for DNA replication

• Complications: GI discomfort, Achilles tendon rupture, superinfection, phototoxicity, cardiac dysrhythmias (QT interval prolongation)

• Interactions: Antacids, dairy products decrease absorption plasma levels of theophylline and warfarin increase with concurrent use

Nursing Administration - Fluroquinolones

• D/C other IV infusions or another IV site when administering cipro IV

• Lower doses for patients who have impaired kidney function

• Administer cipro IV in dilute solution slowly over 60 mins in a large vein.

Sulfonamides

• Prototypes:

  • Trimethoprim-sulfamethoxazole

  • Trimethoprim

• Prevent synthesis of tetrahydrofolate (folic acid derivative, essential for production of DNA, RNA, proteins)

Sulfonamides Complications

• Hypersensitivity (including Stevens-Johnson Syndrome)

• Photosensitivity

• Blood dyscrasias

• Crystalluria

• Kernicterus

• Hyperkalemia

Interactions & Nursing Administration - Sulfonamides

• Increased effects of warfarin, phenytoin, sulfonylurea oral hypoglycemics (monitor levels, give lower dosages during therapy)

• Use back-up contraception method

• Increase fluids (at least 2000 ml/day unless contraindicated)

Urinary Tract Antiseptics

• Nitrofurantoin

  • Injures bacteria by damaging DNA

  • Complications: GI discomfort, hypersensitivity, blood dyscrasias, peripheral neuropathy, headache, drowsiness, dizziness

  • Nursing administration

    • Turns urine rust-yellow to brown and can stain teeth

    • Take with food

    • Avoid crushing, chewing, or opening capsules (possibility of teeth staining)

Antifungals

• Amphotericin B given IV (systemic mycoses); Ketoconazole (superficial and system mycoses); nystatin (Candida infections of intestines, vagina, skin, mouth)

• Complications: Infusion reactions, thrombophlebitis, nephrotoxicity, electrolyte imbalance, bone marrow supression

Interactions & Nursing Administration - Antifungals

• Additive nephrotoxic risk when take with aminoglycosides

• Azoles increase risk of multiple drugs, including digoxin, warfarin, and sulfonylurea antidiabetics drugs

• Nursing Administration

  • Amphotericin B is highly toxic and should be infused slowly (over 4-6 hours IV)

  • Observe solution for precipitation and discard if present (use filter to prevent infusion of undissolved crystals)

Universal Nursing Responsibilities

• Assess for allergies

• Obtain cultures before starting therapy

• Monitor for therapeutic effect

  • GI distress

  • Superinfection (C. diff diarrhea)

  • Hypersensitivity reactions

• Monitor for adverse effects (complications)

• Minitor renal and hepatic functions (as appropriate)

• Ensure correct administration

• Infection control measures

Patient Education

• Complete the full course

• Do not skip doses

• Report any reactions (severe diarrhea, rash or itching, signs of superinfection)

• Do not share medication

Nursing Evaluations of Medication Effectiveness

• Antibiotics are effective when signs and symptoms of infection improve or resolve

  • Clinical improvement

  • Laboratory improvement

  • VS stabilization

  • Radiologic or objective findings (improving chest X-ray in pneumonia, improved wound appearance)

  • Time frame expectation (improvement usually seen within 24-72 hours)