Antibacterial Medications Part II

Common Antibiotic Concerns
  • Nausea, vomiting, diarrhea are common side effects of antibiotic use.
  • Antibiotics must be taken as prescribed to avoid developing antibiotic resistance.
  • Caution is advised for patients with kidney and liver impairments, as these organs are crucial for drug metabolism and excretion, potentially leading to increased drug levels and toxicity.
  • Decreased therapeutic effects of antibiotics may occur due to poor absorption or drug interactions, and increased effects can lead to toxicity, especially in sensitive populations like the elderly or those with organ dysfunction.
  • Rashes, itching, and other allergic reactions, ranging from mild to severe (e.g., anaphylaxis), are common side effects of various antibiotics.
Antibiotics That Interfere with Bacterial Protein Synthesis
Tetracyclines (-cycline)
  • Examples: doxycycline (Vibramycin), tetracycline.
  • Mechanism: Bacteriostatic action (inhibits bacterial growth) by reversibly binding to the 30S30S ribosomal subunit, preventing the attachment of aminoacyl-tRNA.
  • Indications: Used to treat specific gram-positive and gram-negative bacterial infections, including Rocky Mountain spotted fever, chlamydia, H. pylori infection, acne, and various skin infections.
  • Common side effects include:
    • Nausea, vomiting, and diarrhea.
    • Permanent discoloration to teeth (yellow-gray-brown), especially in children under 88 years old and during pregnancy/breastfeeding.
    • Photosensitivity (increased sensitivity to sunlight), requiring patients to use protective clothing and sunscreen.
    • Skin rash.
  • Milk and dairy products, antacids, and iron supplements decrease the effectiveness of tetracyclines, as they bind to the antibiotics and inhibit absorption. Should be taken on an empty stomach.
  • Contraindications: Pregnancy, breastfeeding, and children under 88 years old.
Aminoglycosides (-cin or -mycin)
  • Examples: amikacin, gentamicin, neomycin, tobramycin.
  • Indications: Used for serious gram-negative bacterial infections, including peritonitis, pneumonia, severe UTI infections, bowel preparation (neomycin), and as adjunctive therapy for serious staph infections.
  • Mechanism: Bactericidal antibiotics effective against gram-negative bacteria by irreversibly binding to the 30S30S ribosomal subunit, causing misreading of mRNA and inhibiting protein synthesis.
  • Adverse effects include:
    • **Neurotoxicity**: Symptoms may include tremors, twitching, seizures, decreased level of consciousness, and decreased heart rate/respiratory rate.
    • **Nephrotoxicity**: Symptoms may include elevated blood urea nitrogen (BUN), proteinuria, hematuria, altered urine output (oliguria or anuria), and concentrated urine. Regular monitoring of renal function (BUN, creatinine) is essential.
    • **Ototoxicity**: Symptoms can be ringing in the ears (tinnitus), balance issues, altered hearing, vertigo. Can be irreversible.
  • **Note**: The safety range for aminoglycosides is narrow, requiring careful therapeutic drug monitoring with peak and trough levels to optimize efficacy and minimize toxicity. Typically administered intravenously due to poor oral absorption, except for local effects like bowel decontamination.
Macrolides (-cin or -mycin)
General Information
  • **Mechanism**: Can be bacteriostatic or bactericidal depending on the concentration and organism. They inhibit bacterial protein synthesis by reversibly binding to the 50S50S ribosomal subunit.
  • Useful in treating respiratory infections (e.g., atypical pneumonia, Legionnaires' disease), whooping cough, acne or skin infections, and genitourinary infections (e.g., chlamydia).
  • Common adverse reactions:
    • Abdominal pain and cramping, nausea, vomiting.
    • Photosensitivity.
    • Prolonged QT interval, increasing the risk of cardiac arrhythmias. Caution with other QT-prolonging drugs.
  • Important: Macrolides should not be taken with fruit juices or food for some agents (e.g., erythromycin), as this can decrease their effectiveness. Significant drug interactions, especially with CYP3A43A4 inhibitors/substrates.
  • Examples: azithromycin (Zithromax), erythromycin.
Lincosamides
  • **Agent**: clindamycin (Cleocin).
  • Mechanism: Bacteriostatic, inhibits bacterial protein synthesis by binding to the 50S50S ribosomal subunit.
  • Used primarily for serious staph or strep infections, anaerobic infections, and some protozoal infections.
  • High potential for toxicity, particularly severe **Clostridioides difficile**-associated diarrhea (CDAD) or pseudomembranous colitis, which can be life-threatening.** Contraindicated in patients with certain liver diseases and liver impairments due to its hepatic metabolism.
Antibiotic Drugs That Interfere with DNA/RNA Synthesis
  • This class generally refers to **Fluoroquinolones**.
  • **Mechanism**: Bactericidal, they inhibit bacterial DNA gyrase (topoisomerase II) and topoisomerase IV, enzymes essential for bacterial DNA replication, transcription, repair, and recombination.
  • **Indications**: Commonly used to treat a broad range of infections including lower respiratory infections, bone and joint infections, UTIs, skin infections, STDs, and eye infections.
  • Potential serious side effects include:
    • Ruptured tendons and tendonitis (e.g., Achilles tendon rupture), carrying a **Black Box Warning**, especially in elderly patients or those taking corticosteroids.
    • CNS concerns including insomnia, dizziness, confusion, and hallucinations.
    • Peripheral neuropathy, which can be irreversible.
    • Prolonged QT interval.
    • Photosensitivity.
  • Certain interactions occur; supplements or antacids containing calcium, magnesium, aluminum, iron, or zinc can chelate the drug and significantly decrease effectiveness if taken concomitantly.
  • Examples of fluoroquinolones: ciprofloxacin (Cipro), levofloxacin (Levaquin), ofloxacin (Floxin).
Anti-tubercular Medications
Tuberculosis (TB)
  • Caused by bacteria *Mycobacterium tuberculosis*.
  • Causes approximately 1.41.4 million deaths globally each year and is ranked among the top ten causes of death.
  • Risk Factors: Close living conditions, compromised immune systems (e.g., HIV), and locations at high risk for outbreaks.
Symptoms of TB
  • Common symptoms include:
    • Progressive fatigue.
    • Malaise.
    • Anorexia and weight loss.
    • Chronic cough (often productive cough).
    • Night sweats.
  • Advanced state may exhibit hemoptysis (coughing up blood).
Treatment and Diagnosis
  • Treatment duration: 66 to 1212 months, often requiring multiple medications (multi-drug therapy) to prevent resistance.
  • Medications frequently have significant side effects and interactions with many other medications, especially HIV therapy.
  • Increasing concern over drug-resistant TB; directly observed therapy (DOT) may be necessary to ensure compliance and treatment completion.
  • Diagnosis tools include:
    • TB skin test (screening, e.g., PPD test).
    • Chest X-ray.
    • Sputum studies (smear and culture) to identify and test the TB bacteria for drug susceptibility.
Specific TB Medications
  • **Rifampin (Rifadin)**: Prevents RNA synthesis by inhibiting DNA-dependent RNA polymerase. Common side effects include gastrointestinal upset, red-orange discoloration of body fluids (urine, sweat, tears—warn patients about potential staining of contact lenses), and potential hepatotoxicity. It is a potent inducer of hepatic CYP450450 enzymes, leading to numerous drug interactions.
  • **Isoniazid (INH)**: Prevents DNA synthesis by inhibiting the synthesis of mycolic acid, a crucial component of the mycobacterial cell wall. Common side effects include gastrointestinal distress, jaundice, skin eruptions, peripheral neuropathy (often prevented by co-administration of pyridoxine, vitamin B66), and antabuse reactions (flushing, tachycardia, chills, headache, nausea, vomiting) if alcohol is consumed.
    Hepatotoxicity is a major concern with INH.
Practice Questions
  • **Practice Question 1**: Azithromycin (Zithromax) is available in 250 mg tablets. The patient is instructed to take 750 mg once per day. How many tablets should be taken with each dose? The patient should take 3 tablets of 250 mg.
  • **Teaching provided**: Instruct the patient on the necessity of completing full course therapy, potential side effects (nausea, diarrhea), and to avoid interacting foods.
  • **Practice Question 2**: An avid runner is completing a course of ciprofloxacin (Cipro). What should the nurse be most concerned about? The concern should be about spontaneous tendon rupture, especially in physically active patients, due to the **Black Box Warning** associated with fluoroquinolones.
  • **Practice Question 3**: A patient has just started taking tobramycin. What symptoms should the nurse monitor for? Symptoms of concern include:
    • Tingling in the lower extremities (neurotoxicity).
    • Periods of dizziness (ototoxicity/neurotoxicity).
    • Photosensitivity (not a primary concern for tobramycin; more common with tetracyclines/fluoroquinolones, but generalized rash could occur).
    • Cloudy, concentrated urine output (possible nephrotoxicity).