Hesi antiinfectives ATB

Anti-infective Agents: Comprehensive Study Notes

Anti-infective targets and goals

• Anti-infective agents target foreign organisms or altered host cells to treat infections and cancers.
• Main categories mentioned:
  • Antibiotics
  • Anti-fungal agents
  • Anti-viral agents
  • Anti-neoplastic agents
• Primary goal of anti-infectives:
  • Destroy invading organisms and interrupt how they function so they cannot reproduce, leading to cell death, while trying to avoid harming host cells.
• Important caveat:
  • No anti-infective has been developed that does not affect host cells in some way; immunocompromised patients are at higher risk.
• Populations at risk for adverse effects or complications:
  • Elderly and infants
  • Transplant patients or those on immunosuppressants
  • Cancer patients, HIV/AIDS patients
  • Malnourished patients

Chapter context and exam alignment

• Chapter 7 (Cell Physiology Review) emphasizes:
  • Cell membrane and lipid bilayer importance
  • Receptor sites, histocompatibility antigens (self-identification)
  • Channels (Na, K, Ca, etc.)
  • Mitochondria (ATP production)
  • Lysosomes (digestive enzymes)
• Chapter 8 overview (Anti-infective agents) sets up mechanisms, spectra, and resistance topics to be covered more deeply.
• Note from the instructor: All drugs within PowerPoints and concept maps may appear on exams; if a drug name is used without its class, you must know the class to identify the drug correctly.

Mechanisms of action (how anti-infectives work)

• General mechanisms include:
  • Destroy the cell wall of invading organisms (example: $ext{Penicillin}$)
  • Prevent the pathogen from obtaining essential substances (example: $ext{Sulfonamides}$)
  • Interrupt protein synthesis (example: $ext{Aminoglycosides}$)
  • Interrupt DNA synthesis (example: $ext{Fluoroquinolones}$)
  • Alter cell membrane permeability leading to cell death (some antifungals, antibiotics, and antiprotozoals)
• Key point: Many drugs can have multiple or overlapping mechanisms depending on organism and context.

Spectrum and activity concepts

• Bactericidal vs. bacteriostatic (and fungicidal vs. fungistatic):
  • Bactericidal/fungicidal: drugs that actively kill organisms.
  • Bacteriostatic/fungistatic: drugs that inhibit growth, allowing host defenses to eliminate the pathogen.
• Spectrum breadth:
  • Narrow spectrum: highly selective; targets a limited group of microorganisms.
  • Broad spectrum: not highly selective; acts on a wide variety of microorganisms.
• Clinical implication: Narrow-spectrum use when possible to limit collateral host damage and resistance.

Resistance: how it develops and how to prevent it

• How resistance develops:
  • Pathogen produces an enzyme that deactivates the drug (e.g., penicillinase degrading penicillin).
  • Pathogen reduces drug entry into the cell.
  • Pathogen alters drug binding sites so the drug is no longer effective.
  • Pathogen produces antagonistic chemicals that inactivate or counter the drug.
• Preventing resistance:
  • Use around-the-clock dosing when appropriate (e.g., $q8 ext{h}$ instead of attempting three times daily, $8 ext{ hours}$ apart).
  • Do not use antibiotics for viruses; reserve antibiotics for sensitive organisms.
  • Take drugs exactly as prescribed; do not stop early.
  • Narrow-spectrum therapy when the causative organism is known.
  • Ensure doses are high enough and long enough to eradicate the organism.
  • Consider combination therapy when indicated to enhance efficacy and delay resistance.

Treatment strategy for systemic infections

1) Identify the pathogen: culture from relevant sites (blood, urine, feces, wound bed, mucosa, etc.).
2) Determine sensitivity: perform sensitivity testing; may start with broad-spectrum antibiotics first, then switch to narrow after results.
3) Consider combination therapy when appropriate:

• Smaller doses per drug but potentially more powerful in combination.
• May identify more than one organism; combination can delay resistant strains’ development.

Practical downsides and organ toxicities to monitor

• Kidney toxicity: many anti-infectives are renally excreted; hydration is important.
• GI toxicity: GI lining irritation, N&V, diarrhea, etc.
• Liver toxicity: many drugs metabolized by liver; can lead to hepatitis or liver failure.
• Neurotoxicity: potential nerve tissue damage; specific drugs (e.g., aminoglycosides) can affect cranial nerves.
  • Aminoglycosides can accumulate in the 8th cranial nerve, leading to dizziness and hearing loss.

Specific antibiotic classes and key notes

Aminoglycosides (~micin/~mycin)

• Examples: $ext{Amikacin}, ext{gentamicin}, ext{kanamycin}, ext{neomycin}, ext{streptomycin}, ext{tobramycin}$
• Spectrum and action:
  • Mainly active against gram-negative aerobic bacilli; bactericidal.
• Administration:
  • Poorly absorbed from the GI tract; rapidly absorbed when given IM (peak ~1 hour) or IV.
• Indications:
  • Used for serious infections; less toxic alternatives for less serious infections.
  • May be used if patient cannot take penicillin.
• Contraindications:
  • Allergy to any aminoglycoside; pre-existing hearing loss; renal/hepatic disease; active herpes infection; pregnancy/lactation considerations; myasthenia gravis or Parkinson’s disease due to CNS effects.
• Adverse effects:
  • Ototoxicity and nephrotoxicity; GI effects; potential for superinfections.
• Drug-drug interactions:
  • Synergistic bactericidal effect with penicillin or cephalosporin.
  • Avoid with strong diuretics; caution with anesthetics due to potential for increased neuromuscular blockade.
• Nursing considerations:
  • Close assessment, D.O.T. (nursing Dx, planning, implementation, evaluation) guidance; monitoring of drug levels and renal/hearing function.

Carbapenems (~penem)

• Examples: $ext{Meropenem}, ext{doripenem}, ext{ertapenem}, ext{imipenem-cilastatin}$
• Properties:
  • Broad-spectrum, bactericidal; active against both gram-positive and gram-negative bacteria.
  • Often used for serious infections; sometimes a last-resort option.
• Pharmacokinetics:
  • Rapidly absorbed via IM or IV; PO forms can be dangerous or less effective.
• Contraindications and cautions:
  • Avoid ertapenem in patients < $18$ years old; caution in seizure disorders, meningitis, and lactation.
  • Renal impairment requires dosage adjustment; potential nephrotoxicity and GI issues.
• Adverse effects:
  • C. diff-associated diarrhea, N&V, electrolyte disturbances; seizures, headaches, dizziness (CNS effects).
• Interactions and nursing considerations:
  • Do not use with valproic acid (increased seizure risk).
  • TEACHING focus on assessment, planning, and evaluation.

Cephalosporins (cef- or ceph-)

• Generations and examples:
  • 1st generation: $ext{Cephalexin (Keflex)}$
  • 2nd generation: $ext{Cefoxitin (Mefoxin)}$
  • 3rd generation: $ext{Cefdinir (Omnicef)}, ext{cefotaxime (Claforan)}, ext{ceftriaxone (Rocephin)}$
  • 4th generation: active against MRSA (e.g., cefepime; some consider a 5th generation such as ceftaroline)
• Notes:
  • Similar structure and activity to penicillins; many are given by injection or orally.
  • Important: this class is contraindicated for those allergic to penicillin (though cross-reactivity is variable).
• Spectrum and use:
  • Broad range of infections including respiratory, GI, GU, endocarditis, bone, joint, skin infections; meningitis for some third-generation agents.
• Safety and interactions:
  • Common adverse effects: GI upset (N/V, diarrhea, anorexia), rash; potential hypersensitivity.
  • Interactions: avoid concomitant aminoglycosides due to nephrotoxicity risk; possible interactions with oral anticoagulants (bleeding risk); disulfiram-like reaction with alcohol after administration for some cephalosporins.
• Nursing considerations:
  • Monitor for rash and GI symptoms; check penicillin allergy history; monitor liver and kidney function as needed.

Fluoroquinolones (~floxacin)

• Examples: $ext{Ciprofloxacin (Cipro)}, ext{gemifloxacin}, ext{levofloxacin (Levaquin)}, ext{moxifloxacin}, ext{ofloxacin}, ext{finafloxacin}$
• Spectrum and use:
  • Broad-spectrum against gram-negative bacteria; widely used for urinary tract infections, respiratory infections, skin infections; also used for prevention of anthrax and typhoid fever.
• Formulations:
  • Available in IV, PO, topical forms.
• Pharmacokinetics:
  • Metabolized in the liver; excreted in urine and feces.
• Contraindications and cautions:
  • Allergy to fluoroquinolones; pregnancy or lactation; caution in renal dysfunction; seizures; not recommended for children < $18$ years.
• Adverse effects:
  • Generally mild but include headache, dizziness, insomnia, GI upset; black box warning for tendinitis and tendon rupture, especially in younger than $18$ or older than $60$.
  • Fluoroquinolone-Associated Disability (FQAD) can include fatigue, concentration problems, neuropathies, tendinopathies; potential for long-term mitochondrial damage and other subacute effects (noted in slides as a concern).
• Drug-drug interactions:
  • Chelation with iron, mineral supplements, and antacids (administer 4 hours before or after these supplements).
  • Potential to prolong QT interval; interact with theophylline (dose reduction needed); caution with NSAIDs and corticosteroids (increased risk of CNS stimulation and tendinopathy).
• Nursing considerations and teaching:
  • Instruct patient to take exact dosing, increase fluids, monitor for CNS or GI effects, and report tendon pain or rupture signs.
  • Special note: avoid use in pregnancy and in kids due to safety concerns.

Penicillins (~cillin)

• Variants:
  • Penicillin G (various salts): benzathine, potassium, procaine
  • Extended-spectrum: amoxicillin, ampicillin
  • Penicillinase-resistant: nafcillin, oxacillin
• Uses:
  • Streptococcal, pneumococcal, staphylococcal infections; notable uses include anthrax and syphilis.
• Administration:
  • PO, IM, IV forms available; many have better absorption on an empty stomach with a full glass of water to ensure absorption.
• Contraindications:
  • Allergy to penicillin or to cephalosporins (caution with potential cross-reactivity).
  • Renal disease considerations.
• Adverse effects:
  • GI disturbances; risk of superinfections due to disruption of normal flora.
• Drug-drug interactions:
  • Decreased effectiveness when taken with tetracyclines.
  • Do not administer penicillins and aminoglycosides parenterally at the same time as inactivation of aminoglycosides can occur if given concurrently; usually separate by about 1 hour.
• Nursing considerations:
  • Monitor for allergic reactions, adherence to dosing, and signs of superinfection.

Sulfonamides (Sulfa drugs)

• Examples: $ext{Sulfadiazine}, ext{sulfasalazine}, ext{cotrimoxazole (Bactrim, Septra)}$
• Uses:
  • Older generation, commonly used for UTIs; inexpensive alternative to newer medications; broad activity against gram-negative and gram-positive organisms; some also have anti-inflammatory effects (e.g., sulfasalazine).
• Contraindications:
  • Allergy to sulfa drugs, sulfonylureas, or thiazide diuretics; pregnancy/lactation; kernicterus risk; renal disease or history of kidney stones; elderly patients with increased CNS effects.
• Adverse effects:
  • GI disturbances; renal effects; CNS effects (headache, dizziness); photosensitivity and rash.
• Nursing considerations:
  • Monitor hydration and urine output; counsel on photosensitivity precautions.

Tetracyclines (~clycline)

• Examples: $ext{Tetracycline}, ext{demeclocycline}, ext{doxycycline}, ext{minocycline}$
• Uses:
  • Broad uses including treatment of chlamydia, syphilis, gonorrhea; acne treatment; other infections.
• Important pharmacokinetic notes:
  • Absorption is reduced by food and dairy products; take 1 hour before or 2 hours after meals or dairy; alcohol interactions not noted here but generally advisable to avoid dairy when timing is critical for absorption.
• Contraindications and cautions:
  • Allergy, pregnancy, and lactation; avoid in children < $8$ years and in women who are pregnant or planning pregnancy when possible due to effects on bone/teeth.
  • Caution in renal or hepatic dysfunction.
• Adverse effects:
  • GI distress; hepatotoxicity (potentially fatal); skeletal damage to teeth and bones; photosensitivity and rash.
• Drug interactions:
  • Interactions with penicillin G, digoxin, and oral contraceptives; avoid with mineral salts that reduce absorption; avoid taking with foods that reduce absorption.
• Nursing considerations:
  • Emphasize adherence and avoidance of dairy near dosing; monitor for photo-sensitivity and GI symptoms.

Practical exam tips and study notes

• Exam hint: Know class-to-drug mappings. For example, Streptomycin is an aminoglycoside, and you should be able to identify the class even if the specific drug name is used without the class label.
• Expect questions about mechanism, spectrum, major adverse effects, contraindications, and key drug interactions for each class.
• Knowledge of common sources of resistance and strategies to prevent resistance is frequently tested.

Ethical, philosophical, and practical implications

• Overuse of broad-spectrum antibiotics can disrupt normal flora, promote resistance, and cause collateral damage to patients, especially the immunocompromised.
• The balance between treating infection effectively and minimizing host toxicity requires careful assessment, especially in vulnerable populations (infants, elderly, pregnant patients, transplant recipients, and those with organ dysfunction).
• Transparency with patients about potential long-term adverse effects (e.g., FQAD in fluoroquinolones) is important for informed consent and shared decision-making.

Numerical references and time-based considerations (LaTeX-formatted)

• Dosing intervals and cautions expressed in slides include:
  • q8h dosing interval (every 8 hours): $q8\,\text{h}$
  • Safety cautions such as disulfiram-like reactions with alcohol for certain cephalosporins: ensure avoidance of alcohol during and for $72\,\text{hours}$ after antibiotic discontinuation: $72\ \text{hours}$ after d/c.
  • Age-related cautions: avoidance of fluoroquinolones in patients < $18$ years and caution in patients > $60$ years regarding tendon risk.
• Time-sensitive actions in systemic infection treatment emphasize culture collection times, sensitivity testing durations, and potential rapid escalation to broad-spectrum therapy if culture results are delayed.

Note: exam content and class resources

• This content reflects slides from PowerPoints and concept maps; specific drug names not listed on slides may appear on exams with the drug’s class identified (per instructor note).
• For deeper learning and NCLEX/HESI preparation, review BOX 9.1 and 9.2 referenced in the material for additional details on antibiotic teaching and indications.