Chemotherapy Drugs: Antibacterial Overview

Chemotherapy Drugs

• Anti-infective drugs include antibacterial, antiviral, antifungal, and antiparasitic agents (antiprotozoal or anthelmintic).
• Antibacterial drugs are classified into:
  • Cell wall synthesis inhibitors
  • Protein synthesis inhibitors
  • Folic acid synthesis inhibitors
  • Nucleic acid (DNA/RNA) synthesis inhibitors

Terminology of Antibacterial Drugs

• Bactericidal: directly kill the target organism
• Bacteriostatic: inhibit the growth of the organism
• Broad-spectrum antimicrobials: effective against many strains of microorganisms
• Narrow-spectrum antimicrobials: effective against a few strains
• Culture and sensitivity test: determines the presence of bacteria/fungus and selects the most effective antibiotic
• Sulfonamides were the first therapeutic antibacterial agents.
• Sulfonamides inhibit the synthesis of folic acid (important metabolite in DNA synthesis)
• Sulfamethoxazole is used for the treatment of a wide range of infections (e.g., urinary tract infection, otitis media, bronchitis, pharyngitis, and diarrhea) in combination with trimethoprim.
• Co-trimoxazole is a combination of sulfamethoxazole and trimethoprim (bactericidal)
• Topical uses of sulfonamides include prevention and treatment of skin infections.

Penicillins

• First beta-lactam antibiotics
• Inhibit bacterial cell wall synthesis
• Types of penicillins:
  • Natural penicillin (e.g., penicillin G & penicillin V)
    • Benzathine penicillin (long-acting form): used to treat pharyngitis caused by B-hemolytic streptococci.
  • Broad-spectrum penicillin (e.g., ampicillin & amoxicillin): used with B-lactamase inhibitors (e.g., sulbactam, clavulanic acid) in chest and urinary tract infections
  • Anti-staph penicillin (e.g., flucloxacillin): used in combination with amoxicillin
  • Extended Antipsudomonal penicillin (e.g., carbincillin & ticarcillin)

Adverse Effects of Penicillins

• Penicillin hypersensitivity (anaphylactic shock) is rare with parenteral administration; emergency treatment includes adrenaline, intravenous corticosteroids, antihistamines, and aminophylline.
• Common side effects: skin reactions (skin rashes, urticaria), gastrointestinal disturbances (nausea, vomiting, diarrhea), and hepatitis.

Nursing Considerations

• Review patient history for allergies to penicillin
• Oral penicillin should be taken with plenty of water, avoiding acidic fluids
• Monitor patients for 30 minutes after parenteral administration for allergic reactions
• Dilute IM doses according to manufacturer instructions
• Monitor serum sodium and potassium levels in patients receiving high doses of sodium penicillin, carbenicillin, or ticarcillin
• Women taking oral contraceptives may require a second method of birth control.

Cephalosporins

• Similar to penicillins but more stable against bacterial B-lactamases
• Types:
  • First-generation: oral (cefadroxil) and parenteral (cefazolin)
  • Second-generation: oral (cefaclor) and parenteral (cefuroxime)
  • Third-generation: parenteral (cefotaxime, cefoperazone, cefotaxime, ceftriaxone), oral (cefixime)
  • Fourth-generation: parenteral (cefepime)

Cephalosporins Adverse Effects

• Common side effects include allergies, local irritation, renal toxicity, and blood disorders.

Fluoroquinolones

• Bactericidal by interfering with bacterial DNA synthesis
• Broad spectrum antibacterial activity
• Uses: Urinary tract infections, gastrointestinal infections, respiratory infections, genital, bone, joint infections.
• Adverse effects: Gastrointestinal upset (nausea, vomiting, diarrhea), central nervous system effects (headache, dizziness), photosensitivity, liver damage, and tendon rupture (especially in the Achilles tendon), and disturbance in blood glucose level.

Inhibitors of Protein Synthesis

• Tetracyclines, aminoglycosides, chloramphenicol, macrolides
  • Tetracyclines (e.g., doxycycline): absorption is inhibited by dairy products, calcium, aluminum, and iron
  • Adverse effects include gastrointestinal upset and liver damage, and dental discoloration and bone growth abnormalities in children.

Erythromycin

• Macrolide
• Primarily used for Chlamydia, Mycoplasma, and Legionella infections
  • Adverse effects include gastrointestinal upset, liver toxicity, and cholestatic hepatitis.

Other Antibiotics

• Pertussis: Erythromycin is the drug of choice.
• Acne: Erythromycin can be used as an alternative to penicillin.
• Mycoplasma pneumoniae infection: Erythromycin can be used.

This quiz covers the classification and terminology of antibacterial drugs within chemotherapy. It highlights the mechanisms of action, types of antibacterial drugs, and key terms such as bactericidal and bacteriostatic. Test your knowledge on the effectiveness and use of various antimicrobial agents.