Chapter 26: Penicillins, Other Beta-Lactams, and Cephalosporins

CHAPTER 26: PENICILLINS, OTHER BETA-LACTAMS, AND CEPHALOSPORINS

INTRODUCTION AND COPYRIGHT

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PATHOPHYSIOLOGY OF DISEASE-PRODUCING ORGANISMS

• Bacteria

  • Bacilli: Elongated or rod-shaped bacteria.

  • Cocci: Spherical bacteria.

  • Subcategories:

    • Staphylococci: Cocci that appear in clusters.

    • Streptococci: Cocci arranged in chains.

GRAM STAINING: ANOTHER CLASSIFICATION OF BACTERIA

• Gram Positive

  • Characteristics: Retains a purple stain.

  • Examples:

  • Staphylococcus aureus

  • Streptococcus pneumoniae

  • Group B Streptococcus (GBS)

  • Clostridium perfringens

• Gram Negative

  • Characteristics: Does not retain stain.

  • Examples:

  • Neisseria meningitides

  • Escherichia coli

  • Haemophilus influenzae

ANTIBACTERIALS / ANTIBIOTICS

• Definition: Substances that inhibit bacterial growth or kill bacteria and other microorganisms.

• Antibacterials:

  • Chemicals produced by one kind of microorganism to inhibit or kill bacteria.

• Antibiotics: Inhibit growth of bacteria.

  • Bacteriostatic drugs: Inhibit bacterial growth.

  • Bactericidal drugs: Kill bacteria.

ANTIBACTERIAL ACTION

• Mechanisms include:

  • Inhibition of bacterial cell wall synthesis.

  • Alteration of membrane permeability.

  • Inhibition of protein synthesis.

  • Inhibition of synthesis of bacterial RNA and DNA.

  • Interference with metabolism within the cell.

BODY DEFENSES

• Factors that affect the immune response:

  • Age

  • Nutrition

  • Immunoglobulins

  • Circulation

  • White Blood Cells (WBCs)

  • Organ function

RESISTANCE TO ANTIBACTERIALS

(1 OF 2)

• Characteristics of Resistance:

  • Inherent resistance: Pre-existing resistance to a drug.

  • Acquired resistance: Develops due to mutation or gene transfer.

  • Pathogen behavior: Pathogen continues to grow after antibacterial administration.

• Health Care Acquired Infections:

  • MRSA (Methicillin Resistant Staphylococcus aureus)

  • VREF (Vancomycin Resistant Enterococcus faecium)

  • VRSA (Vancomycin Resistant Staphylococcus aureus)

(2 OF 2)

• Causes of Antibiotic Misuse:

  • Use for viral infections.

  • Use when no bacterial infection is present.

  • Incorrect usage (skipping doses, not completing the full prescription).

  • Cross-resistance: Resistance that occurs between antibacterial drugs with similar actions.

ANTIBACTERIALS: GENERAL ADVERSE REACTIONS

• Allergic Reactions:

  • Hypersensitivity, rash, pruritus, hives, anaphylactic shock.

• Superinfection:

  • Secondary infection occurring when normal flora is killed.

  • Usual sites for superinfection:

  • Mouth

  • Skin

  • Respiratory tract

  • Genitourinary tract

  • Intestines

• Organ Toxicity:

  • Effects on ear, liver, kidney.

ANTIBACTERIAL SPECTRUM

• Narrow Spectrum

  • Primarily effective against one type of bacteria.

  • Examples: Penicillin, Erythromycin.

• Broad Spectrum

  • Effective against both gram-positive and gram-negative bacteria.

  • Examples: Tetracycline, Cephalosporins.

  • Usage: Commonly used when the offending microorganism has not been identified by culture and sensitivity (C&S) testing.

PENICILLINS

• Structure: Characterized by a beta-lactam ring.

• Action:

  • Inhibit bacterial cell wall synthesis.

  • Can be both bacteriostatic and bactericidal, depending on the drug type and dosage.

• Types of Penicillins:

  • Basic penicillins

  • Broad-spectrum penicillins

  • Penicillinase-resistant penicillins

  • Extended-spectrum penicillins

BETA-LACTAM AND BETA-LACTAMASES

• BETA-LACTAM:

  • A ring structure in some antibiotics such as penicillins and cephalosporins that interfere with bacterial cell wall synthesis by inhibiting bacterial enzymes. All beta-lactam ring structures are crucial for killing bacteria.

• BETA-LACTAMASE:

  • An enzyme produced by some bacteria that can break down beta-lactam antibiotics by cleaving the beta-lactam ring, rendering the antibiotics ineffective.

PENICILLINS PHARMACOKINETICS

• General Characteristics:

  • Works quickly and spreads well through body fluids.

  • Only minimally altered by the liver.

  • Quickly eliminated via urine.

PENICILLINS PHARMACODYNAMICS

• Mechanism of Action:

  • Works by killing bacteria (bactericidal activity).

  • Destroys bacteria by breaking down their cell wall, causing them to burst and die.

PENICILLINS CONTINUED

CONTRAINDICATIONS

• Allergy to penicillin or other beta-lactam antibiotics.

THERAPEUTIC EFFECTS

• Evaluate the effectiveness of penicillin by determining if the infection has resolved and assessing for side effects.

DRUG INTERACTIONS

• Penicillins may reduce the effectiveness of oral contraceptives.

• When administered with aminoglycosides via IV, the actions of both drugs may be inactivated.

PENICILLIN SIDE EFFECTS / ADVERSE REACTIONS

• Possible Side Effects:

  • Hypersensitivity and anaphylaxis.

  • Superinfection.

  • Tongue discoloration, stomatitis, and glossitis.

  • Gastrointestinal distress.

  • Arthralgia (joint pain).

  • Clostridium difficile-associated diarrhea.

CLINICAL JUDGMENT: PENICILLINS

(1 OF 2)

• Concept:

  • Recognize cues indicating infection.

  • Assess for allergies to penicillin or cephalosporins.

  • Evaluate lab results, particularly hepatic enzymes.

• Analyze Cues and Prioritize:

  • Hypothesis might include tissue injury, nausea, vomiting.

  • Generate solutions: The patient’s WBC count should be within normal limits.

(2 OF 2)

• Take Action:

  • Obtain a sample for lab culture and antibiotic sensitivity testing before starting antibiotic therapy.

  • Monitor for superinfection, especially in patients on high doses for prolonged periods.

  • Examine the patient for allergic reactions, especially after the first and second doses.

  • Educate patients to complete the entire prescribed course of antibiotics.

  • Evaluate Outcomes: Overall response to treatment and side effects.

CEPHALOSPORINS

• Characteristics:

  • Beta-lactam structure similar to penicillins.

• Pharmacokinetics: Comparable to penicillins.

• Uses: Effective in treating a variety of infections including:

  • Pharyngitis, tonsillitis, otitis media.

  • Respiratory infections, skin infections, intra-abdominal infections, bone and joint infections, urinary tract infections, gynecologic infections, sexually transmitted infections (STIs), bacteremia, and sepsis.

• Pharmacodynamics:

  • Inhibit bacterial cell wall synthesis.

  • Effective bactericidal activity.

CEPHALOSPORIN GENERATIONS

(1 OF 2)

• First Generation

  • Mostly effective against gram-positive bacteria.

  • Example: Cephazolin.

  • Vulnerability: Destroyed by beta-lactamases.

• Second Generation

  • Effective against both gram-positive and gram-negative bacteria.

  • Examples: Cefoxitin, Cefaclor.

  • Beta-lactamase sensitivity: Only some are affected.

(2 OF 2)

• Third Generation

  • Example: Ceftriaxone.

  • Broad-spectrum antibacterial activity and effective against Pseudomonas aeruginosa.

  • Resistant to beta-lactamases.

• Fourth Generation

  • Example: Cefepime.

  • Broad-spectrum activity and highly resistant to beta-lactamases.

  • Good penetration into cerebrospinal fluid.

• Fifth Generation

  • Example: Tazobactam.

  • Broad-spectrum activity, highly resistant to beta-lactamases.

  • Effective against MRSA.

CEPHALOSPORIN SIDE EFFECTS / ADVERSE REACTIONS

• Potential Reactions:

  • Anaphylaxis and superinfection.

  • Headache, dizziness, gastrointestinal distress.

  • Increased bleeding tendencies.

  • Elevated hepatic enzymes.

  • Nephrotoxicity.

  • Clostridium difficile-associated diarrhea.

CEPHALOSPORIN INTERACTIONS

• Drug Interactions:

  • Alcohol: May cause a disulfiram-like reaction leading to flushing, dizziness, headache, nausea, vomiting, muscular cramps.

  • Anticoagulants: May increase bleeding risk.

  • Cefotetan: May enhance the effects of other medications such as aminoglycosides, salicylates, and warfarin.

  • Loop Diuretics, Aminoglycosides, and Vancomycin: Can increase nephrotoxicity.

CLINICAL JUDGMENT: CEPHALOSPORINS

(1 OF 2)

• Concept:

  • Recognize cues indicating infection.

  • Assess for allergy to cephalosporins or penicillins.

  • Evaluate lab results, especially renal and liver function.

• Analyze Cues and Prioritize:

  • Hypothesis could include tissue injury, nausea, vomiting.

  • Generate solutions with goals for patient outcomes.

(2 OF 2)

• Take Action:

  • Culture the infected area before cephalosporin treatment is initiated.

  • Instruct patients to report any signs of superinfection.

  • Educate on the importance of completing the treatment course.

  • Monitor for hypersensitivity reactions.

  • Advise taking medication with food if gastric irritation occurs.

  • Evaluate Outcomes: Assess overall effectiveness and any adverse effects noted.

BETA-LACTAMASE INHIBITORS

• Action:

  • Inhibit bacterial beta-lactamases, thus extending the antimicrobial spectrum.

  • Note: Not given alone, but combined with penicillinase-sensitive penicillin for enhanced effect.