Ch. 38 Antibiotics Part 1 pg. 589-610

Digestible Summary of Antibiotics Part 1

1. General Principles of Antibiotic Therapy

• Antibiotics: Drugs that kill or inhibit bacterial growth.

• Goal: Eliminate infections while minimizing harm to the patient.

• Key Considerations:

  • Right drug, right dose, right duration

  • Patient-specific factors (age, renal/liver function, allergies, immune status, pregnancy, etc.)

  • Avoid unnecessary antibiotic use to prevent resistance

2. How Antibiotics Work

• Bactericidal → Kills bacteria directly (e.g., penicillins, cephalosporins).

• Bacteriostatic → Inhibits bacterial growth, allowing the immune system to fight the infection (e.g., tetracyclines, sulfonamides).

3. Antiseptics vs. Disinfectants

🔹 Nursing Considerations: Ensure proper use to avoid toxicity or skin irritation.

4. Risks of Antibiotic Overuse & Resistance

• Overuse leads to drug-resistant bacteria (e.g., MRSA, C. difficile).

• Antimicrobial Stewardship promotes responsible antibiotic use.

• Key Strategies:

  • Only prescribe antibiotics when necessary

  • Ensure correct antibiotic & dosage

  • Educate patients on completing full courses

5. Classification of Antibiotics & Key Information

📌 Beta-lactamase inhibitors (e.g., clavulanic acid, tazobactam) are combined with beta-lactam antibiotics to prevent bacterial resistance.

6. Adverse Effects & Prevention Strategies

7. Superinfections (Secondary Infections)

• Caused by antibiotic-induced imbalance in normal flora (e.g., C. difficile, yeast infections).

• Prevention:

  • Use antibiotics only when necessary.

  • Probiotics may help maintain gut flora balance.

8. Nursing Care Plan for Patients on Antibiotics

Assessment

✅ Assess for allergies (penicillin cross-reactivity).
✅ Monitor for superinfection signs (diarrhea, thrush).
✅ Check renal & liver function before prescribing certain antibiotics.

Interventions

💊 Administer with/without food as required (e.g., tetracyclines on empty stomach, macrolides with food).
🚨 Educate patients on full course adherence to prevent resistance.
💦 Encourage hydration (especially for sulfonamides).

9. Key Takeaways

✔ Antibiotics should only be used when necessary to prevent resistance.
✔ Know the differences between bactericidal vs. bacteriostatic antibiotics.
✔ Understand the major side effects & nursing considerations of common antibiotic classes.
✔ Be aware of superinfection risks & preventive measures.

Digestible Summary of Microbial Infections & Health Care–Associated Infections

1. Microbial Infections: Overview

• Microorganisms (bacteria, viruses, fungi, protozoa) exist everywhere—some are beneficial while others cause infection when conditions change.

• Body defenses protect against infections:

  • Physical barriers → Skin, respiratory mucosa.

  • Physiological defenses → Gastric acid, immune responses (antibodies, phagocytes).

Bacteria Classification: Morphology & Gram Staining

• Bacteria are classified by shape & Gram stain response.

  • Gram-positive bacteria → Stain purple, have a thick peptidoglycan cell wall.

  • Gram-negative bacteria → Stain red, have a thin peptidoglycan wall + two protective membranes (harder to treat).

🔹 Why Gram Staining Matters?
✔ Gram-negative bacteria are more resistant to antibiotics due to their complex structure.

2. Infection Development & Symptoms

• Occurs when the body’s defenses are compromised, allowing microorganisms to multiply.

• Symptoms of infection:

  • Systemic → Fever, chills, fatigue, weight loss, elevated WBC count.

  • Local → Redness, swelling, pain, pus formation.

• Immunocompromised & older adults may not show typical infection signs!

🔹 Colonization vs. Infection
✔ Colonization = Bacteria present but no active infection → Does NOT require antibiotics.
✔ Infection = Bacteria multiplying & causing harm → Requires treatment.

3. Health Care–Associated Infections (HAIs)

• Acquired in hospitals or health care settings (≥48 hours after admission).

• More dangerous than community infections due to antibiotic resistance.

• Common HAIs:

  • UTIs (often from catheters).

  • Surgical site infections.

  • Bloodstream infections (IV lines, central lines).

  • Pneumonia (ventilators, aspiration).

Common Drug-Resistant Pathogens

🔹 Key Facts:
✔ 1 in 25 hospitalized patients develops an HAI.
✔ Over 70% of HAIs are preventable!

4. Preventing Health Care–Associated Infections

✔ Handwashing is the #1 method to prevent HAIs.
✔ Proper use of disinfectants & antiseptics.

Disinfectants vs. Antiseptics

🔹 Key Differences:
✔ Disinfectants (cidal) → Kills bacteria.
✔ Antiseptics (static) → Stops bacterial growth (but does not necessarily kill).

5. Key Takeaways

✔ Gram-negative bacteria are harder to treat due to their protective outer membrane.
✔ Colonization ≠ Infection → Antibiotics should be used only when necessary.
✔ HAIs are a major cause of illness & death due to antibiotic-resistant bacteria.
✔ Hand hygiene & proper infection control measures prevent most HAIs.

Digestible Summary of Pharmacology & Antibiotic Therapy

1. General Uses of Antibiotics

Antibiotics are used for three main purposes:
✔ Empiric Therapy → Given before identifying the exact bacteria (based on likely cause).
✔ Definitive Therapy → Given after lab tests confirm the specific bacteria; uses a narrow-spectrum antibiotic.
✔ Prophylactic Therapy → Given before surgery or other high-risk situations to prevent infection.

🔹 Key Concept
✔ Broad-spectrum antibiotics → Work against many bacteria, but increase resistance risk.
✔ Narrow-spectrum antibiotics → Target specific bacteria; preferred once lab results confirm the pathogen.

2. Monitoring Antibiotic Therapy

✔ Therapeutic Response → Symptoms improve (e.g., fever decreases, WBC count normalizes).
✔ Subtherapeutic Response → Infection does not improve (due to resistance, wrong drug, or poor drug absorption).
✔ Toxicity → Antibiotic levels too high → causes adverse reactions (e.g., rash, joint pain, breathing difficulty).

3. Superinfections

🔹 Happens when antibiotics kill normal bacteria, allowing harmful microbes to take over.
✔ Example: Vaginal yeast infections after taking antibiotics.
✔ Serious Superinfection: C. difficile (C. diff)

• Caused by disruption of normal gut bacteria.

• Symptoms: Watery diarrhea, fever, abdominal pain.

• Precaution: Patient must be placed in isolation if C. diff is confirmed.

4. Antibiotic Resistance: A Major Concern

🚨 Overuse & misuse of antibiotics = Resistance!
✔ Main Causes of Resistance:

• Overprescribing antibiotics (especially for viral infections like colds).

• Patients stopping antibiotics early (bacteria survive & mutate).

💡 Solution:
✔ Only use antibiotics when necessary.
✔ Finish the entire prescribed course, even if you feel better.

5. Food-Drug & Drug-Drug Interactions

🔹 Solution:
✔ Avoid taking these antibiotics with dairy or antacids.
✔ Take antibiotics at least 2 hours apart from interacting foods/drugs.

6. Host Factors Affecting Antibiotic Selection

✔ Age → Children & elderly may need dosage adjustments.
✔ Allergies → Penicillins & sulfonamides are common allergy triggers!
✔ Pregnancy → Some antibiotics (teratogens) can cause birth defects.
✔ Genetic Factors → Some people metabolize drugs slowly, increasing toxicity risk.
✔ Site of Infection → Certain antibiotics don’t penetrate well into lungs, bones, or abscesses.

🔹 Important Allergy Considerations
✔ Mild reaction (e.g., nausea) ≠ Allergy.
✔ Severe reaction (e.g., anaphylaxis, rash, hives, swelling, breathing issues) = Do NOT give that antibiotic!

7. Key Takeaways

✔ Empiric therapy is used before labs confirm the infection.
✔ Definitive therapy uses narrow-spectrum antibiotics once bacteria are identified.
✔ Superinfections (e.g., C. diff) occur when antibiotics kill normal flora.
✔ Antibiotic resistance is a serious problem—only take antibiotics when necessary!
✔ Allergy history, pregnancy, organ function, and infection site influence antibiotic selection.

Digestible Summary of Antibiotics & Their Mechanisms of Action

1. Classification of Antibiotics

Antibiotics are grouped based on their chemical structure, spectrum of activity, and mechanism of action.

Main Antibiotic Classes:

2. Mechanisms of Action: How Antibiotics Work

Antibiotics target bacteria in 4 main ways:

✔ 1. Inhibiting Cell Wall Synthesis → Bacteria cannot form a protective barrier, leading to death.

• Examples: Penicillins, Cephalosporins

✔ 2. Inhibiting Protein Synthesis → Stops bacteria from making proteins needed for survival.

• Examples: Macrolides, Aminoglycosides, Tetracyclines

✔ 3. Inhibiting DNA/RNA Replication → Prevents bacterial reproduction.

• Examples: Quinolones (Ciprofloxacin, Levofloxacin)

✔ 4. Inhibiting Metabolism (Antimetabolites) → Blocks bacteria from making essential nutrients.

• Examples: Sulfonamides (Bactrim)

🔹 Why This Matters?
✔ Different antibiotics attack bacteria in different ways, which is important for selecting the right drug.
✔ Bacteria can develop resistance to specific mechanisms, requiring alternative antibiotics.

3. The Challenge of Resistance & Changing Drug Indications

• Bacteria constantly evolve → making some antibiotics ineffective.

• Antibiotic resistance = fewer treatment options (e.g., MRSA, VRE).

• New guidelines & treatments emerge yearly → Always check current resources (pharmacists, hospital protocols).

• Antimicrobial stewardship → Programs in hospitals ensure responsible antibiotic use to prevent resistance.

4. Key Takeaways

✔ Antibiotics target bacteria through 4 main mechanisms (cell wall, protein synthesis, DNA/RNA, metabolism).
✔ Different classes of antibiotics treat different infections—broad-spectrum drugs increase resistance risks.
✔ Drug resistance is a major challenge—always consult up-to-date resources for proper antibiotic selection.
✔ Antimicrobial stewardship is essential to preserve antibiotic effectiveness for future use.

Here's a well-structured, digestible version of the material you posted, organized into sections for easier reading and retention.

Sulfonamides: Overview and Pharmacology

Introduction

• First antibiotics developed; still widely used today.

• Commonly used sulfonamide: Sulfamethoxazole combined with Trimethoprim (SMX-TMP) (Bactrim, Septra, co-trimoxazole).

• Other uses of sulfonamides:

  • Sulfisoxazole + Erythromycin (used in pediatrics).

  • Sulfasalazine (treats ulcerative colitis & rheumatoid arthritis, NOT used as an antibiotic).

Mechanism of Action

• Bacteriostatic (prevents bacterial growth but doesn’t kill bacteria).

• Inhibits folic acid synthesis, preventing bacterial DNA and RNA formation.

• Competitive inhibition: Blocks para-aminobenzoic acid (PABA), preventing bacterial metabolism.

• Trimethoprim (not a sulfonamide) works similarly by inhibiting tetrahydrofolate synthesis.

Indications (Uses)

• Broad-spectrum: Effective against both Gram-positive and Gram-negative bacteria.

• Achieves high concentration in kidneys → Primary use: UTIs.

• Commonly treated bacteria:

  • E. coli, Enterobacter, Klebsiella, Proteus mirabilis, Proteus vulgaris, Staphylococcus aureus (including MRSA).

• Other uses:

  • Respiratory infections (less effective against Streptococcus species).

  • Opportunistic infections in HIV patients (Pneumocystis jirovecii pneumonia).

  • Outpatient treatment of MRSA infections.

• Often paired with urinary analgesic (Phenazopyridine, Pyridium) for UTI pain relief.

Contraindications (Who Should NOT Take Sulfonamides)

• Known sulfa drug allergy (“sulfa allergy” or “sulfur allergy”).

• Pregnant women at term and infants <2 months old (risk of kernicterus).

• Patients taking Celecoxib (Celebrex) (risk of cross-reactivity).

Adverse Effects

• Common allergic reaction: "Sulfa allergy"—delayed rash, fever, photosensitivity.

• Skin reactions: Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), exfoliative dermatitis.

• Other effects:

  • Blood disorders: Agranulocytosis, hemolytic anemia, thrombocytopenia.

  • GI issues: Nausea, vomiting, diarrhea, pancreatitis, hepatotoxicity.

  • Renal effects: Crystalluria, toxic nephrosis.

  • Neurologic: Headache, peripheral neuritis, convulsions.

🔹 Clinical Tip: Take sulfonamides with 8 oz. of water to prevent crystalluria!

Drug Interactions

• Enhances effects of:

  • Sulfonylureas (diabetes drugs) → Increases risk of hypoglycemia.

  • Phenytoin (antiseizure drug) → Increases toxicity.

  • Warfarin (blood thinner) → Increases bleeding risk.

• Can reduce effectiveness of oral contraceptives → Use backup birth control.

• Can increase risk of cyclosporine-induced nephrotoxicity.

🔹 Clinical Tip: Sulfonamides have MANY drug interactions—monitor closely!

Dosage & Administration

• Oral (PO) & Intravenous (IV) forms available.

• Standard dose for UTI and other infections:

  • PO: 160 mg trimethoprim / 800 mg sulfamethoxazole (every 12 hours).

  • IV: 8–20 mg/kg/day (dose based on trimethoprim component).

Pharmacokinetics (How the Drug Moves in the Body)

Key Takeaways

✔ Bacteriostatic antibiotic that inhibits folic acid synthesis.
✔ Broad-spectrum activity, commonly used for UTIs, respiratory infections, and MRSA.
✔ Avoid in sulfa-allergic patients, pregnant women (term), and infants (<2 months).
✔ Common side effects: Allergic reactions, skin reactions, GI issues, and crystalluria.
✔ Multiple drug interactions—monitor warfarin, sulfonylureas, phenytoin, and oral contraceptives.
✔ Drink plenty of water to avoid kidney complications.

Here’s a well-structured and digestible summary of the Beta-Lactam Antibiotics and Penicillins to help you retain the key information efficiently.

Beta-Lactam Antibiotics: Overview

What Are Beta-Lactam Antibiotics?

• Named after the beta-lactam ring in their structure.

• Main mechanism of action: Inhibit bacterial cell wall synthesis, causing bacterial cell death.

• Four major subclasses:

  1. Penicillins

  2. Cephalosporins

  3. Carbapenems

  4. Monobactams

• Time-dependent killing: Effectiveness depends on how long drug levels remain above the minimum inhibitory concentration (MIC).

Beta-Lactamase & Resistance

• Some bacteria produce beta-lactamase, an enzyme that breaks the beta-lactam ring, making antibiotics ineffective.

• To combat resistance, beta-lactamase inhibitors are combined with certain penicillins:

  • Clavulanic acid

  • Tazobactam

  • Sulbactam

  • Avibactam

• Common combinations:

  • Amoxicillin/clavulanic acid (Augmentin)

  • Piperacillin/tazobactam (Zosyn)

  • Ampicillin/sulbactam (Unasyn)

  • Ticarcillin/clavulanic acid (Timentin)

Penicillins: Overview

Classification of Penicillins

Mechanism of Action

• Binds to Penicillin-Binding Proteins (PBPs) → Disrupts peptidoglycan synthesis in bacterial cell walls.

• Weakens the cell wall, causing cell lysis (rupture) and bacterial death.

• Bactericidal (kills bacteria).

Indications (Uses)

✔ Used for infections caused by susceptible bacteria, including:

• Gram-positive bacteria: Streptococcus, Enterococcus, Staphylococcus.

• Extended-spectrum penicillins (Zosyn) → Cover Gram-negative & anaerobic bacteria.

• Common infections treated:

  • Respiratory infections

  • Skin infections

  • Urinary tract infections (UTIs)

  • Ear infections

  • Pneumonia

  • Sepsis

Contraindications

• Main contraindication: Allergy to penicillins.

• Cross-reactivity with cephalosporins:

  • Older reports: 1-4% cross-reactivity.

  • Newer data: <1% unless severe allergy is documented.

  • Cephalosporins may be safe unless patient has a history of anaphylaxis, throat swelling, or hives with penicillin.

🔹 Clinical Tip: Trade names don’t always end in “-cillin”!

• Example: Zosyn (Piperacillin/tazobactam), Augmentin (Amoxicillin/clavulanic acid).

• Be sure to check for penicillin allergies when giving these drugs!

Adverse Effects

✔ Most common: Allergic reactions (0.7% - 4% of patients).
✔ Symptoms of allergy:

• Skin reactions: Rash, itching (pruritus), hives (urticaria), angioedema.

• Severe cases: Anaphylaxis (life-threatening).

• Other rare reactions: Stevens-Johnson Syndrome (SJS), exfoliative dermatitis. ✔ GI Issues: Nausea, vomiting, diarrhea, oral candidiasis (yeast infection in the mouth). ✔ Hematologic: Anemia, bone marrow suppression, granulocytopenia. ✔ Metabolic Effects: Electrolyte imbalances (hyperkalemia, hypernatremia, alkalosis).

🔹 Clinical Tip: Allergic reactions are more common with injectable penicillins than oral forms.

Drug Interactions

🔹 Clinical Tip: Patients on warfarin or oral contraceptives need extra monitoring when taking penicillins.

Dosage & Administration

✔ Dosages vary by type of penicillin and infection severity. ✔ Routes of administration:

• Penicillin G → IV or IM (injection).

• Penicillin V → Oral (tablet/liquid).

• Aminopenicillins (Amoxicillin, Ampicillin) → Oral or IV.

• Extended-spectrum (Piperacillin/Ticarcillin) → IV for severe infections.

Key Takeaways

✔ Beta-lactam antibiotics disrupt bacterial cell walls, causing bacterial death.
✔ Penicillins treat a wide range of infections (mostly gram-positive, some gram-negative with extended-spectrum).
✔ Beta-lactamase inhibitors (Clavulanic acid, Tazobactam) prevent resistance.
✔ Main risk: Allergic reactions (rash, hives, anaphylaxis).
✔ Be cautious of cross-reactivity with cephalosporins (but risk is low).
✔ Penicillins can interact with warfarin, methotrexate, NSAIDs, and birth control pills.
✔ Be careful with trade names like Zosyn & Augmentin—check for penicillin allergies!

Here’s a structured and digestible summary of Penicillin Drug Profiles, making it easier to absorb the key information.

Penicillin Drug Profiles

General Information

✔ Class: Beta-Lactam Antibiotics
✔ Pregnancy Category: B (Generally safe for pregnancy)
✔ Primary Action: Inhibits bacterial cell wall synthesis (bactericidal).
✔ Main Contraindication: Penicillin allergy.

1. Natural Penicillins

Drugs:

• Penicillin G (Benzathine, Procaine, Potassium)

• Penicillin V Potassium (Pen-Vee K)

✔ Penicillin G:

• 3 salt forms:

  • Benzathine & Procaine: Long-acting IM injection.

  • Potassium: IV use.

• Never give benzathine/procaine IV → Fatal due to thick consistency.

• Use: Syphilis (single injection often sufficient).

✔ Penicillin V Potassium:

• Only available as an oral drug.

• Use: Streptococcal infections, pneumonia, mild skin infections.

Pharmacokinetics: Penicillin G

2. Penicillinase-Resistant Penicillins

Drugs:

• Nafcillin

• Cloxacillin

• Dicloxacillin

• Oxacillin

✔ Designed to resist destruction by penicillinase-producing bacteria (e.g., Staphylococcus species).
✔ Nafcillin is available only as an injectable drug.
✔ Cloxacillin & Dicloxacillin are oral-only drugs.
✔ Oxacillin is available in both oral & injectable forms.

🔹 Some strains of S. aureus (e.g., MRSA) are resistant to these drugs and require alternative antibiotics.

Pharmacokinetics: Nafcillin

3. Aminopenicillins

Drugs:

• Amoxicillin (Amoxil)

• Ampicillin

✔ Contain an amino (-NH2) group, allowing better gram-negative coverage than natural penicillins.
✔ Still active against some gram-positive organisms.

Amoxicillin

• Most commonly prescribed aminopenicillin.

• Uses: Respiratory infections, otitis media (ear infection), sinusitis, UTIs, skin infections.

• Higher doses needed in pediatrics due to Streptococcus pneumoniae resistance.

• Given orally (tablet or suspension).

• Can be taken with or without food.

Pharmacokinetics: Amoxicillin

Ampicillin

• Available in three salt forms:

  • Ampicillin anhydrous/trihydrate → Oral use

  • Ampicillin sodium → IV/IM use

• Less frequently used due to resistance.

• Often combined with sulbactam (beta-lactamase inhibitor) → Ampicillin/sulbactam (Unasyn).

• Sulbactam enhances effectiveness by preventing bacterial resistance.

Pharmacokinetics: Ampicillin

4. Extended-Spectrum Penicillins

Drugs:

• Piperacillin

• Ticarcillin

• Carbenicillin (Rarely used alone)

✔ Broader coverage against gram-positive, gram-negative, and anaerobic bacteria.
✔ Commonly used for serious hospital-acquired infections.

💉 Often used in combination with beta-lactamase inhibitors:

• Piperacillin + tazobactam = Zosyn (IV)

• Ticarcillin + clavulanate = Timentin (IV)

✔ Common use: Empiric therapy for serious infections (e.g., intra-abdominal infections, pneumonia, sepsis, Pseudomonas infections).
✔ Only available for intravenous (IV) use.

Dosage Summary for Selected Penicillins

Key Takeaways

✔ Penicillins are classified into four major types:

1. Natural Penicillins (e.g., Penicillin G, Penicillin V) → Best for Streptococcus infections.

2. Penicillinase-Resistant Penicillins (e.g., Nafcillin) → Resist beta-lactamase, used for Staphylococcus infections.

3. Aminopenicillins (e.g., Amoxicillin, Ampicillin) → Enhanced gram-negative coverage.

4. Extended-Spectrum Penicillins (e.g., Piperacillin, Ticarcillin) → Broadest spectrum, used for severe infections.

✔ Common Drug Combinations to Combat Resistance:

• Ampicillin/Sulbactam (Unasyn)

• Amoxicillin/Clavulanic Acid (Augmentin)

• Piperacillin/Tazobactam (Zosyn)

• Ticarcillin/Clavulanate (Timentin)

✔ Penicillins are generally safe, but be cautious with allergies.
✔ Zosyn and Timentin are commonly used in hospitalized patients for serious infections.

Here’s a structured and digestible summary of Cephalosporins, making it easy to understand and retain key information.

Cephalosporins Overview

✔ Class: Beta-Lactam Antibiotics
✔ Mechanism of Action: Bactericidal – Inhibit bacterial cell wall synthesis.
✔ Pregnancy Category: B (Generally safe for pregnancy).
✔ Spectrum of Activity: Broad-spectrum, affecting gram-positive and gram-negative bacteria.
✔ Cross-Sensitivity: 1%–4% of patients allergic to penicillin may react to cephalosporins.
✔ Main Adverse Effects: Mild diarrhea, abdominal cramps, rash, itching, redness, and swelling.
✔ Contraindications: Severe penicillin allergy (anaphylaxis history) and known hypersensitivity.

Cephalosporin Generations

There are five generations of cephalosporins, each improving in gram-negative coverage while losing some gram-positive coverage.

🔹 First-Generation Cephalosporins

✔ Strongest gram-positive coverage but limited gram-negative coverage.
✔ Used for: Skin infections, surgical prophylaxis, mild respiratory infections.

Common Drugs:

• IV: Cefazolin

• PO: Cephalexin, Cefadroxil

🔹 Second-Generation Cephalosporins

✔ Better gram-negative coverage than first-generation.
✔ Some drugs also cover anaerobes (e.g., Cefoxitin).
✔ Used for: Abdominal infections, pneumonia, surgical prophylaxis.

Common Drugs:

• IV: Cefoxitin, Cefuroxime, Cefotetan

• PO: Cefuroxime axetil, Cefaclor, Cefprozil

🔹 Third-Generation Cephalosporins

✔ Even stronger gram-negative coverage but less gram-positive coverage.
✔ Some can cross the blood-brain barrier (e.g., ceftriaxone, cefotaxime) → Used for meningitis.
✔ Used for: Severe infections (e.g., sepsis, pneumonia, UTIs, Lyme disease, gonorrhea).

Common Drugs:

• IV: Ceftriaxone, Ceftazidime, Cefotaxime

• PO: Cefdinir, Cefpodoxime, Ceftibuten

💡 Special Notes:

• Ceftriaxone (Rocephin): Long half-life, dosed once daily, crosses blood-brain barrier, used for meningitis, gonorrhea, and Lyme disease.

• Ceftazidime (Fortaz): Best Pseudomonas coverage among cephalosporins.

🔹 Fourth-Generation Cephalosporins

✔ Excellent gram-negative coverage, including Pseudomonas.
✔ Some gram-positive activity.
✔ Used for: Severe hospital-acquired infections (e.g., pneumonia, sepsis).

Common Drug:

• IV: Cefepime

🔹 Fifth-Generation Cephalosporins

✔ Covers BOTH gram-positive (including MRSA) and gram-negative organisms.
✔ Used for: MRSA, resistant gram-negative infections.

Common Drugs:

• IV: Ceftaroline (Teflaro), Ceftolozane/Tazobactam (Zerbaxa)

💡 Special Notes:

• Ceftaroline (Teflaro): Only cephalosporin that covers MRSA.

• Ceftolozane/Tazobactam (Zerbaxa): Enhanced gram-negative coverage, including resistant Pseudomonas.

Cephalosporins: Drug Interactions

Cephalosporins: Key Takeaways

✔ Gram-negative coverage increases with each new generation.
✔ Cross-sensitivity with penicillin exists (1%–4%).
✔ Cephalosporins DO NOT cover:

• Enterococcus

• Atypicals (e.g., Mycoplasma, Chlamydia)

• Anaerobes (except some 2nd-generation cephalosporins).
  ✔ Ceftriaxone (Rocephin) is a first-line treatment for:

• Gonorrhea

• Meningitis

• Lyme disease

Dosage Summary for Selected Cephalosporins

💡 Quick Study Tips:

✅ First Generation → Strongest gram-positive, mild gram-negative.
✅ Second Generation → Better gram-negative, some anaerobic.
✅ Third Generation → Even better gram-negative, can cross blood-brain barrier (meningitis).
✅ Fourth Generation → Broadest spectrum, Pseudomonas.
✅ Fifth Generation → Covers MRSA (Ceftaroline).

Here's a digestible summary of Carbapenems, making it easier to read, understand, and retain key points.

Carbapenems Overview

✔ Class: Beta-Lactam Antibiotics
✔ Mechanism of Action: Bactericidal – Inhibit bacterial cell wall synthesis.
✔ Broadest spectrum of any antibiotics to date – Covers gram-positive, gram-negative, and anaerobic bacteria.
✔ Reserved for: Complicated infections in hospitalized patients.
✔ Seizure Risk: Can cause drug-induced seizures, especially in high doses or patients with renal impairment.
✔ Cross-Allergy with Penicillins: Low risk, but avoid in patients with anaphylactic reactions to penicillin.
✔ Administration: Must be infused over 60 minutes.

🔹 Carbapenem Drugs & Indications

🔹 Drug Profile: Imipenem/Cilastatin (Primaxin)

✔ Combination:

• Imipenem → Broad-spectrum carbapenem.

• Cilastatin → Blocks kidney enzyme dehydropeptidase, preventing breakdown of imipenem.

✔ Spectrum of Activity:

• Covers gram-positive, gram-negative, and anaerobic bacteria.

• Resistant to beta-lactamase enzymes.

✔ Used For:

• Serious infections: Bone, joint, skin, soft tissue infections.

• Bacterial endocarditis (S. aureus).

• Intraabdominal infections.

• Pneumonia, UTIs, pelvic infections, and sepsis.

✔ Contraindications:

• Severe penicillin allergy (anaphylaxis).

• Lidocaine allergy (IM form contains lidocaine).

✔ Seizure Risk:

• 1.5% risk with standard doses.

• 10% risk with high doses (>500 mg q6h).

• Higher risk in elderly & renally impaired patients.

✔ Drug Interactions:

• Cyclosporine, Ganciclovir, Probenecid → Increased CNS effects (seizures).

✔ Pharmacokinetics:

🔹 Special Notes on Other Carbapenems

✔ Meropenem (Merrem)

• More activity against Enterobacteriaceae than imipenem.

• Only carbapenem indicated for bacterial meningitis.

• Less gram-positive coverage than imipenem.

✔ Ertapenem (Invanz)

• Once-daily dosing → Easier administration.

• Not active against Pseudomonas or Enterococcus.

• Used for intraabdominal infections, UTIs, skin infections.

✔ Doripenem (Doribax)

• Less seizure potential than Imipenem.

• Used for intraabdominal infections, UTIs.

• ❌ NOT for pneumonia (higher mortality risk).

✔ Imipenem/Cilastatin + Relebactam (Recarbrio)

• Stronger against resistant infections.

• Beta-lactamase inhibitor (Relebactam) added.

💡 Key Takeaways

✅ Carbapenems are last-line antibiotics – Used for serious, resistant infections.
✅ Broadest coverage of any antibiotic class (Gram-positive, Gram-negative, and Anaerobes).
✅ Seizure risk, especially in renal failure patients.
✅ Imipenem must be given with cilastatin to prevent breakdown in kidneys.
✅ Doripenem is NOT used for pneumonia (increased mortality).
✅ Meropenem is the only carbapenem for meningitis.
✅ Ertapenem has once-daily dosing but lacks Pseudomonas coverage.

Monobactams: Aztreonam (Azactam)

✔ Class: Beta-Lactam Antibiotic (Monobactam)
✔ Mechanism of Action: Bactericidal – Inhibits bacterial cell wall synthesis, leading to cell lysis.
✔ Coverage: Only aerobic gram-negative bacteria (e.g., E. coli, Klebsiella, Pseudomonas).
✔ Special Use: Safe alternative for patients with penicillin allergy needing gram-negative coverage.
✔ Indications:

• Moderate-to-severe systemic infections

• UTIs

• Intraabdominal & gynecologic infections (often used in combination with other antibiotics).
  ✔ Dosage Form: Injectable only (IV/IM).
  ✔ Contraindications: Known drug allergy (but minimal cross-reactivity with penicillins/cephalosporins).

🔹 Adverse Effects

✔ Common Side Effects:

• Rash

• Nausea

• Vomiting

• Diarrhea

🔹 Pharmacokinetics

💡 Key Takeaways

✅ Gram-negative coverage only (no gram-positive or anaerobic activity).
✅ Often used in penicillin-allergic patients requiring beta-lactam therapy.
✅ Used for systemic infections & UTIs.
✅ Injectable only (IV/IM).
✅ Minimal cross-reactivity with other beta-lactams.

Macrolide Antibiotics

✔ Class: Protein Synthesis Inhibitors
✔ Mechanism of Action: Bacteriostatic (but bactericidal at high doses) – Inhibit bacterial protein synthesis by binding to the 50S ribosomal subunit.
✔ Drugs in This Class:

• Erythromycin (oldest, more GI side effects)

• Azithromycin (Zithromax) (better tolerated, long duration)

• Clarithromycin (Biaxin) (better tolerated, used for H. pylori)

• Fidaxomicin (Dificid) (specific for C. difficile infections)

🔹 Indications (What They Treat)

✔ Respiratory Infections: Streptococcus pyogenes, Haemophilus influenzae
✔ Skin and Soft Tissue Infections
✔ Sexually Transmitted Infections (STIs): Gonorrhea, Chlamydia, Syphilis
✔ Atypical Bacteria: Mycoplasma, Legionella (Legionnaires’ disease), Campylobacter
✔ Opportunistic Infections:

• Mycobacterium avium-intracellulare complex (MAC) (common in HIV/AIDS patients)

• Helicobacter pylori (H. pylori) ulcers (Clarithromycin + Amoxicillin + Omeprazole)
  ✔ Prokinetic Effect (Erythromycin): Used in diabetic gastroparesis (delayed stomach emptying).

🔹 Contraindications

✔ Known drug allergy
✔ QT Prolongation Risk: Avoid in patients with heart disease or who take drugs that prolong the QT interval.
✔ Liver Disease: Since macrolides are metabolized in the liver, caution is required.

🔹 Adverse Effects

💡 Azithromycin & Clarithromycin have fewer GI effects than erythromycin.

🔹 Drug Interactions

✔ Metabolized in the Liver (CYP-450):

• Increases levels of carbamazepine, cyclosporine, theophylline, warfarin → toxicity risk.
  ✔ Oral Contraceptives: May reduce effectiveness → Use backup contraception.
  ✔ QT Prolongation Risk: Avoid with moxifloxacin, pimozide, thioridazine.
  ✔ Avoid Statins: Clarithromycin & Erythromycin + Simvastatin or Lovastatin → Increased risk of muscle toxicity.

💡 Azithromycin has fewer drug interactions compared to other macrolides.

🔹 Dosages

💡 Azithromycin has the longest half-life and can be dosed once daily.

🔹 Pharmacokinetics

💡 Key Takeaways

✅ Treats respiratory, STI, atypical, & opportunistic infections.
✅ Azithromycin & Clarithromycin are better tolerated than Erythromycin.
✅ Erythromycin has a prokinetic effect (helps with gastroparesis).
✅ Beware of QT prolongation & drug interactions (especially with warfarin, statins, & theophylline).
✅ Azithromycin has a long half-life, allowing once-daily dosing.

Tetracyclines Overview

✔ Class: Protein Synthesis Inhibitors
✔ Mechanism of Action: Bacteriostatic – Inhibit bacterial protein synthesis by binding to the 30S ribosomal subunit.
✔ Drugs in This Class:

• Natural Tetracyclines: Demeclocycline, Oxytetracycline, Tetracycline

• Semisynthetic Tetracyclines: Doxycycline, Minocycline

• Glycylcycline: Tigecycline (Tygacil) (used for resistant bacteria)

🔹 Indications (What They Treat)

✔ Bacterial Infections:

• Gram-Positive & Gram-Negative Bacteria

• Rickettsial Infections (Rocky Mountain spotted fever, typhus)

• Chlamydia Infections

• Mycoplasma pneumoniae (Atypical pneumonia)

• Lyme Disease & Syphilis (alternative for penicillin-allergic patients)

• Acne Treatment (commonly used for moderate-to-severe acne)

• H. pylori Peptic Ulcers (part of combination therapy)

✔ Non-Antibiotic Uses:

• Demeclocycline inhibits ADH → Used for SIADH (Syndrome of Inappropriate Antidiuretic Hormone Secretion).

🔹 Contraindications

✔ Pregnant & Nursing Women: Risk of fetal skeletal retardation and tooth discoloration in newborns.
✔ Children < 8 Years: Permanently stains developing teeth.
✔ Severe Kidney or Liver Disease: Can accumulate and cause toxicity.

🔹 Adverse Effects

💡 Tetracyclines cause PHOTOSENSITIVITY – patients should wear sunscreen & avoid prolonged sun exposure.

🔹 Drug Interactions

✔ Absorption ↓ by:

• Dairy Products (Milk, Cheese)

• Antacids

• Iron Supplements

• Calcium, Magnesium, & Enteral Feedings
  → Take tetracyclines 1 hour before or 2 hours after these substances.

✔ Increased Bleeding Risk when combined with Warfarin (Coumadin).
✔ Decreased Effectiveness of Oral Contraceptives → Use backup birth control.
✔ Do NOT take with bactericidal antibiotics (e.g., penicillins, cephalosporins) – antagonistic effects.

🔹 Dosages

💡 Tigecycline is reserved for resistant infections like MRSA & complicated intraabdominal infections.

🔹 Pharmacokinetics

💡 Doxycycline has a long half-life, so it can be taken once or twice daily.

💡 Key Takeaways

✅ Broad-Spectrum Activity – Used for Chlamydia, Mycoplasma, Rickettsia, Lyme disease, acne.
✅ Avoid in Pregnant Women & Children – Causes tooth discoloration & skeletal effects.
✅ Do NOT take with dairy, antacids, or iron – Reduces absorption.
✅ Increased Risk of Sunburn – Wear sunscreen & avoid prolonged sun exposure.
✅ Reduces Oral Contraceptive Effectiveness – Use additional birth control.

Case Study: Patient-Centered Care - Antibiotic Therapy

Patient Background:

• Mr. G. is a resident of an assisted care facility following a stroke.

• He now has pneumonia (left lower lobe) with productive cough & low-grade fever.

• Medications Ordered:

  • Piperacillin/tazobactam (Zosyn) 2.25 g IV q8h

  • Theophylline (Theo-Dur) 300 mg PO q12h

  • Warfarin (Coumadin) 2 mg PO every evening

  • Maalox PRN for GI upset

  • Ibuprofen 400 mg PO PRN for pain

• Prescriber Orders:

  • Blood cultures from two different sites.

  • Start antibiotic "as soon as possible".

1⃣ Why is Tazobactam Added to Piperacillin (Zosyn)?

✔ Piperacillin is a broad-spectrum beta-lactam antibiotic.
✔ Tazobactam is a beta-lactamase inhibitor.
✔ Some bacteria produce beta-lactamase, an enzyme that destroys beta-lactam antibiotics like piperacillin.
✔ Tazobactam protects piperacillin from degradation, making it effective against resistant bacteria (e.g., Pseudomonas, Enterobacter, and some anaerobes).

👉 Bottom Line: Tazobactam extends piperacillin’s effectiveness against beta-lactamase-producing bacteria, making it more potent for treating pneumonia.

2⃣ Which Order Should the Nurse Implement First?

✅ Blood Cultures First! ✔ Blood cultures must be drawn BEFORE starting the antibiotic to correctly identify the causative organism.
✔ If the antibiotic is given first, it may interfere with culture results, leading to inaccurate identification and potential antibiotic resistance.
✔ After obtaining blood cultures, start Zosyn ASAP to prevent worsening infection.

👉 Order of Actions:
1⃣ Draw blood cultures from two different sites.
2⃣ Start IV Zosyn infusion.
3⃣ Administer other medications as scheduled (monitoring for interactions).

3⃣ Potential Drug Interactions with Zosyn

⚠ Major Drug Interactions:

💡 Nursing Considerations:
✔ Monitor INR & signs of bleeding (bruising, petechiae) due to warfarin interaction.
✔ Monitor theophylline levels (therapeutic range: 10-20 mcg/mL).
✔ Separate Maalox & Zosyn administration by at least 2 hours to avoid interference.
✔ Monitor renal function (BUN/creatinine) due to possible nephrotoxicity.

4⃣ Monitoring Parameters for Zosyn Effectiveness

✔ Clinical Improvement:

• ↓ Fever

• ↓ Productive cough

• ↓ WBC count

• ↓ Shortness of breath ✔ Vital Signs Stabilization:

• Afebrile (temperature normalizing)

• Stable blood pressure & heart rate ✔ Laboratory Monitoring:

• WBC count trending toward normal (4,000–10,000/mm³)

• Negative follow-up blood cultures ✔ Oxygenation:

• Improved breath sounds

• ↓ Crackles in the left lower lung

• Stable oxygen saturation (SpO₂)

💡 Nursing Considerations:
✔ Monitor for superinfection (C. difficile, thrush, vaginal yeast infection).
✔ Check for allergic reactions (rash, hives, anaphylaxis).
✔ Watch for renal impairment (BUN/creatinine levels).

💡 Key Takeaways

✅ Draw blood cultures before starting Zosyn.
✅ Tazobactam prevents beta-lactamase from breaking down piperacillin.
✅ Monitor for drug interactions (warfarin, theophylline, Maalox, ibuprofen).
✅ Check for improvement in symptoms & lab values to evaluate effectiveness.