Antibiotics

Chapter 9: Antibiotics

General Overview of Antibiotics

• Definition: Antibiotics are chemicals that inhibit specific bacteria.

• Methods of Production:

  • By living microorganisms.

  • By synthetic manufacture.

  • Through genetic engineering in some cases.

Types of Antibiotics

• Bacteriostatic:

  • Function: Inhibit the growth of bacteria.

• Bactericidal:

  • Function: Kill bacteria directly.

Signs of Infection

• Common Symptoms:

  • Fever

  • Lethargy

  • Elevated white blood cell count

  • Classic signs of inflammation:

  • Redness

  • Swelling

  • Heat

  • Pain

Goal of Antibiotic Therapy

• Main Objective: Decrease the population of the invading bacteria to a point at which the human inflammatory/immune system can effectively deal with the pathogen.

Treatment Selection

• Culture:

  • Identification of the causative organism.

• Sensitivity Testing:

  • Determination of which antibiotic will best kill or control the organism.

Bacteria Classification

• Gram-positive:

  • The cell wall retains a stain or resists decolorization with alcohol.

• Gram-negative:

  • The cell wall loses a stain or is decolorized by alcohol.

• Aerobic:

  • Depend on oxygen for survival.

• Anaerobic:

  • Do not use oxygen.

Bacteria and Resistance to Antibiotics

• Adaptation: Bacteria adapt to their environment.

• Resistance Development: The longer an antibiotic has been in use, the greater the chance that the bacteria will develop into a resistant strain.

• Consequences of Antibiotic Use: May result in development of superinfections or overgrowth of resistant pathogens.

Aminoglycosides #1

• Purpose: Used to treat serious infections caused by primarily aerobic gram-negative bacilli.

• Common Medications:

  • Amikacin (Amikin)

  • Gentamicin (Garamycin)

  • Neomycin (Mycifradin)

  • Plazomicin (Zemdri)

  • Streptomycin (generic)

  • Tobramycin (Bethkis, TOBI, Tobrex)

Aminoglycosides #2

• Characteristic: Bactericidal.

• Actions:

  • Inhibit protein synthesis in susceptible strains of aerobic gram-negative bacteria.

  • Irreversibly bind to a unit of the bacteria ribosomes, leading to misreading of the genetic code and cell death.

Aminoglycosides #3

• Pharmacokinetics:

  • Absorption: Poorly absorbed from the GI tract, but rapidly absorbed after IM injection, reaching peak level within 1 hour.

  • Distribution: Widely distributed throughout the body, crosses the placenta and enters human milk.

  • Excretion: Excreted unchanged in the urine.

Aminoglycosides #4

• Contraindications and Cautions:

  • Known allergy to any aminoglycosides, renal disease, preexisting hearing loss, myasthenia gravis, or parkinsonism.

  • Use caution during pregnancy; utilize lower doses in patients with renal impairment.

  • Risk for nephrotoxicity and ototoxicity highlighted.

Aminoglycosides #5

• Adverse Effects: Serious and limit usefulness.

  • CNS effects.

  • Renal toxicity.

  • GI effects.

  • Cardiac effects.

  • Hypersensitivity reactions.

• Drug-Drug Interactions:

  • Synergistic bactericidal effect with penicillins or cephalosporins.

  • Use caution with nephrotoxic medications.

  • Increased neuromuscular blockade with certain drugs.

Question #1

• Statement: Because of the adverse effects of the aminoglycosides, it is important to teach the patient to restrict fluids and eat 6 small meals daily.

• Response: False.

  • Rationale: Teach the patient to try to drink a lot of fluids and to maintain nutrition even though nausea, vomiting, and diarrhea may occur.

Carbapenems #1

• Definition: Broad-spectrum antibiotics effective against gram-positive and gram-negative bacteria.

• Common Medications:

  • Doripenem (Doribax)

  • Ertapenem (Invanz)

  • Imipenem–cilastatin (Primaxin)

  • Imipenem–cilastatin–relebactam (Recarbrio)

  • Meropenem (Merrem IV)

  • Meropenem–vaborbactam (Vabomere)

Carbapenems #2

• Characteristic: Bactericidal.

• Actions:

  • Inhibit cell membrane synthesis, leading to cell death.

• Indications:

  • Treatment of serious infections caused by susceptible bacteria.

  • Treatment of serious intra-abdominal, urinary tract, skin and skin structure, bone and joint, and gynecological infections.

Carbapenems #3

• Pharmacokinetics:

  • Rapidly absorbed if given IM and reach peak level at the end of the infusion if given IV.

  • Widely distributed throughout the body; ability to cross the placenta or enter human milk varies by drug.

  • Excreted unchanged in the urine with an average half-life of 1 to 4 hours.

Carbapenems #4

• Contraindications and Cautions:

  • Known allergy to any of the carbapenems or beta-lactams.

  • Use caution during pregnancy and lactation.

  • Regular testing of renal function recommended.

Carbapenems #5

• Adverse Effects:

  • GI tract effects.

  • Superinfections.

  • CNS effects.

• Drug-Drug Interactions:

  • Consider alternative if the patient is taking valproic acid.

  • Avoid concurrent use of imipenem with ganciclovir.

Cephalosporins #1

• Characteristics: Similar to penicillins in structure and activity.

• Common Medications:

  • First Generation:

  • Cefazolin (generic)

  • Cefadroxil (generic)

  • Cephalexin (Keflex)

  • Second Generation:

  • Cefaclor (Ceclor)

  • Cefotetan (generic)

  • Cefoxitin (generic)

  • Cefprozil (generic)

  • Cefuroxime (Zinacef)

  • Third Generation:

  • Cefdinir (Omnicef)

  • Cefotaxime (Claforan)

  • Cefpodoxime (generic)

  • Ceftazidime (Ceptaz, Tazicef)

  • Ceftriaxone (Rocephin)

  • Fourth and Other:

  • Cefepime (Maxipime)

  • Cefiderocol (Fetroja)

  • Ceftaroline (Teflaro)

  • Ceftazidime–avibactam (Avycaz)

  • Ceftolozane–tazobactam (Zerbaxa)

Cephalosporins #2

• Action: Interfere with the cell wall–building ability of bacteria when they divide.

• Indications: Treatment of infections caused by susceptible bacteria.

Cephalosporins #3

• Pharmacokinetics:

  • Primarily excreted unchanged in urine.

  • Eliminated primarily by the liver.

  • Cross the placenta and enter human milk.

Cephalosporins #4

• Contraindications and Cautions:

  • Allergies to cephalosporins or penicillins.

  • Hepatic or renal impairment.

  • Pregnancy or lactation; reserved for appropriate situations due to resistance.

Cephalosporins #5

• Adverse Effects:

  • GI tract effects are the most common.

  • CNS symptoms.

  • Nephrotoxicity.

  • Superinfections.

• Drug-Drug Interactions:

  • Increased nephrotoxicity risk with concurrent administration of aminoglycosides.

  • Increased bleeding possible with warfarin.

Question #2

• Scenario: Writing a plan of care for a patient receiving cefaclor (Ceclor).

• Appropriate Nursing Conclusion:

  • B. Impaired comfort related to GI or CNS effects of drug.

• Rationale: Nursing conclusions regarding drug therapy include:

  • Impaired comfort related to GI or CNS effects of drug, superinfection risk, and knowledge deficit regarding drug therapy.

  • Planning includes ensuring patient understanding of drug therapy, performing culture and sensitivity tests, and monitoring renal function.

Fluoroquinolones #1

• Characteristics: Synthetic class of antibiotics with a broad spectrum of activity.

• Common Medications:

  • Ciprofloxacin (Cipro)

  • Delafloxacin (Baxdela)

  • Levofloxacin (Levaquin)

  • Moxifloxacin (Avelox)

  • Ofloxacin (generic)

Fluoroquinolones #2

• Characteristic: Bactericidal.

• Actions:

  • Enter bacterial cell by passive diffusion.

  • Interfere with action of DNA enzymes, leading to cell death.

• Indications:

  • Treating infections caused by susceptible strains of gram-positive and gram-negative bacteria.

  • Effective for urinary tract, respiratory tract, and skin infections.

  • Some used to prevent or treat postexposure anthrax infection.

Fluoroquinolones #3

• Pharmacokinetics:

  • Absorbed from the GI tract.

  • Metabolized in the liver.

  • Excreted in urine and feces.

  • Widely distributed in the body; crosses the placenta and enters human milk.

Fluoroquinolones #4

• Contraindications and Cautions:

  • Some warnings related to potential serious adverse effects.

  • Known allergy to any fluoroquinolone.

  • Not recommended for use in pregnant or lactating patients except under specific circumstances.

  • Renal dysfunction; associated with damage to developing cartilage.

Fluoroquinolones #5

• Adverse Effects:

  • Most serious include tendinitis, tendon rupture, peripheral neuropathy, CNS effects, prolonged QT interval, C. difficile diarrhea, liver toxicity.

  • Common effects include headache, dizziness, insomnia, depression.

  • GI and immunological effects noted.

• Drug-Drug Interactions:

  • Therapeutic effect decreased when administered with iron salts, sucralfate, multivitamins, calcium or magnesium supplements, and antacids.

  • Drugs that increase QTc interval include warfarin, NSAIDs.

Question #3

• Scenario: Identify a contraindication for receiving a fluoroquinolone.

• Options:

  • Over 65 years

  • Weight under 100 pounds

  • C. Allergy to Cipro (correct answer)

  • History of cancer.

• Rationale: Fluoroquinolones are contraindicated in patients with a known allergy to any fluoroquinolone.

Penicillins and Penicillinase-Resistant Antibiotics #1

• Overview: First antibiotics introduced for clinical use.

• Types:

  • Natural Penicillins:

  • Penicillin G benzathine (Bicillin L.A., Permapen)

  • Penicillin G potassium (Pfizerpen)

  • Penicillin G procaine

  • Penicillin V (Penicillin-VK)

  • Aminopenicillins:

  • Amoxicillin (Amoxil)

  • Ampicillin (generic)

  • Combination medications.

Penicillins and Penicillinase-Resistant Antibiotics #2

• Characteristics: Bactericidal.

• Action: Interfere with the ability of susceptible bacteria to build their cell walls.

• Indications:

  • Treatment of streptococcal, pneumococcal, staphylococcal infections, etc.

  • Antipseudomonal penicillins have the widest spectrum of activity.

• Pharmacokinetics:

  • Rapidly absorbed from the GI tract.

  • Excreted unchanged in the urine.

  • Enters human milk.

Penicillins and Penicillinase-Resistant Antibiotics #3

• Contraindications and Cautions:

  • Allergies to penicillin or other allergens.

  • Renal disease.

  • Pregnant or lactating patients.

Sulfonamides #1

• Function: Drugs that inhibit folic acid synthesis.

• Medications:

  • Sulfadiazine (generic).

  • Cotrimoxazole or trimethoprim–sulfamethoxazole (Septra, Bactrim).

Sulfonamides #2

• Characteristics: Bacteriostatic.

• Action: Block para-aminobenzoic acid to prevent synthesis of folic acid in susceptible bacteria.

• Indications:

  • Treatment of infections caused by gram-negative and gram-positive bacteria.

  • Inexpensive and effective treatment for UTIs and trachoma.

Sulfonamides #3

• Pharmacokinetics:

  • Teratogenic.

  • Distributed into human milk.

  • Absorbed from the GI tract.

  • Metabolized in the liver; excreted in urine.

Sulfonamides #4

• Contraindications and Cautions:

  • Known allergy to any sulfonamide or to thiazide or loop diuretics.

  • Pregnancy and lactation.

  • Renal disease or history of kidney stones.

  • Older adults.

Sulfonamides #5

• Adverse Effects:

  • GI effects

  • Renal effects

  • CNS effects

  • Bone marrow depression

  • Dermatological effects.

• Drug-Drug Interactions:

  • Antidiabetic agents.

  • Medications that increase hyperkalemia risk.

  • Cyclosporine.

Tetracyclines #1

• Overview: Developed as semisynthetic antibiotics based on the structure of a common soil mold.

• Common Medications:

  • Tetracycline (generic).

  • Demeclocycline (generic).

  • Doxycycline (Doryx, Acticlate).

  • Eravacycline (Xerava).

  • Omadacycline (Nuzyra).

  • Minocycline (Arestin, Minocin).

  • Sarecycline (Seysara).

Tetracyclines #2

• Characteristics: Bacteriostatic.

• Action:

  • Inhibit protein synthesis in a wide range of bacteria, leading to the inability of bacteria to multiply.

  • Toxic to humans at high concentrations.

• Indications:

  • Treatment of various infections caused by susceptible strains of bacteria.

  • Particularly used for infections where penicillin is contraindicated.

Tetracyclines #3

• Pharmacokinetics:

  • Adequately absorbed from the GI tract.

  • Concentrated in the liver; excreted unchanged in the urine.

  • Cross the placenta and pass into human milk.

• Contraindications and Cautions:

  • Known allergy to tetracyclines.

  • Not recommended during pregnancy and lactation.

  • Not recommended for children younger than 8 years.

Tetracyclines #4

• Adverse Effects:

  • GI effects.

  • Skeletal effects.

  • Superinfections.

  • Local effects.

• Drug-Drug Interactions:

  • Concurrent use can decrease tetracycline absorption.

  • Administer on an empty stomach with water due to drug-food interactions.

Question #4

• Statement: Sulfonamides should not be given with cyclosporine.

• Response: True.

  • Rationale: Risk of nephrotoxicity rises when sulfonamides are taken with cyclosporine.

Antimycobacterials #1

• Overview: Mycobacteria include pathogens causing TB and leprosy.

• First-Line Drugs for TB Treatment:

  • Isoniazid (generic)

  • Rifampin (Rifadin)

  • Pyrazinamide (generic)

  • Ethambutol (Myambutol)

  • Rifabutin (Mycobutin)

  • Rifapentine (Priftin)

• Leprostatic Drug:

  • Dapsone (generic).

Antimycobacterials #2

• Action: Most act on the DNA of bacteria leading to lack of growth and eventual bacterial death.

• Indications:

  • Treatment of TB and leprosy.

• Pharmacokinetics:

  • Generally well absorbed from the GI tract.

  • Metabolized in the liver; excreted in the urine.

  • Cross the placenta and enter human milk.

Antimycobacterials #3

• Contraindications and Cautions:

  • Known allergy to these agents.

  • Severe renal or hepatic failure.

  • Pregnancy.

• Adverse Effects:

  • CNS effects.

  • GI irritation.

• Drug-Drug Interactions:

  • Combinations that increase risk of hepatotoxicity.

  • Histamine reactions.

Other Antibiotics

• Lincosamides:

  • Bacteriostatic; clindamycin (Cleocin), lincomycin (Lincocin).

• Lipoglycopeptides:

  • Bactericidal; telavancin (Vibativ), dalbavancin (Dalvance), oritavancin (Orbactiv), vancomycin (Vancocin, Firvanq).

• Macrolides:

  • Bactericidal or bacteriostatic; erythromycin (Ery-Tab, Eryc), azithromycin (Zithromax), clarithromycin (Biaxin), fidaxomicin (Dificid).

• Oxazolidinones:

  • Tedizolid (Sivextro), linezolid (Zyvox).

• Monobactam Antibiotic:

  • Bactericidal; aztreonam (Azactam).

Question #5

• Scenario: The patient has tuberculosis. Which medication will the provider prescribe?

• Options:

  • A. Isoniazid (correct answer)

  • Vancomycin

  • Azithromycin

  • Aztreonam.

• Rationale: Isoniazid is specifically indicated for the treatment of M. tuberculosis; the other drugs are not indicated for tuberculosis.