Antibiotics & Anti-infectives – Exam Notes

Top 6 Test Tips

1. Finish the full course → prevents superinfection (e.g., C. diff, MRSA).

2. Accidental pregnancy → with -cillins (penicillin, amoxicillin) & -cyclines (doxycycline).

   • Oral contraceptives ineffective → use backup contraception (IUD, condoms).

3. No alcohol → antibiotics + alcohol = liver stress.

   • Special risk: metronidazole (Flagyl) → violent vomiting with ETOH (during & 3 days after).

4. No food (MTF) – take on empty stomach:

   • M = Macrolides (azithromycin)

   • T = Tetracyclines (doxycycline)

   • F = Fluoroquinolones (levofloxacin)

5. No sun (FTS) – photosensitivity:

   • F = Fluoroquinolones (levofloxacin, ciprofloxacin)

   • T = Tetracyclines (doxycycline)

   • S = Sulfa drugs (TMP-SMX, glyburide, thiazides, loops).

6. “-Mycin/-Micin” = toxic to ears & kidneys (aminoglycosides + vancomycin).

   • Ototoxicity: tinnitus, vertigo, loss of balance.

   • Nephrotoxicity: ↑ BUN (>20), ↑ Creatinine (>1.3), ↓ urine (<30 mL/hr).

   • Peaks & troughs: too high = kidneys die, too low = infection grows.

Drug Classes & Key Points

1. Penicillins (-cillin) & Cephalosporins (Cef-/Ceph-)

• MOA: weaken/destroy bacterial cell wall.

• Pregnancy safe.

• Cross-sensitivity allergy → do not give if allergic to either.

• NCLEX key: anaphylaxis risk (stop med → assess reaction → epi ready).

• Penicillins: oral contraceptive failure; monitor bleeding/platelets.

• Cephalosporins: cause diarrhea; do NOT treat C. diff.

2. Aminoglycosides (-mycin, -micin)

• Examples: gentamicin, tobramycin, neomycin.

• Toxicity: oto- & nephrotoxic.

• Labs: monitor peaks/troughs (therapeutic 10–20).

• Assess: hearing changes, balance, kidney labs, urine output.

• Contraindicated: neuromuscular disease.

3. Glycopeptides (Vancomycin)

• Indications: MRSA, C. diff.

• Toxicity: oto- & nephrotoxic (same as aminoglycosides).

• Special risks:

  • Red Man Syndrome → rapid infusion → flushing, hypotension, rash → slow infusion ≥60 min.

  • Thrombophlebitis → burns veins → give via central line (PICC).

• Differentiate from allergy:

  • RMS = flushing/itching only.

  • Anaphylaxis = hives, angioedema, wheezing → stop med + epi.

4. Macrolides (-thromycin)

• Examples: azithromycin, erythromycin.

• Risks:

  • Prolonged QT interval → cardiac arrest risk → monitor ECG.

  • Hepatotoxic → monitor ALT/AST, avoid acetaminophen.

• Not nephrotoxic.

• Side effects: N/V common (don’t stop therapy).

5. Tetracyclines (-cycline)

• Example: doxycycline.

• Risks:

  • Not safe in pregnancy.

  • Tooth discoloration (children).

  • Photosensitivity → sunblock.

• Administration teaching:

  • Empty stomach, full glass of water.

  • Stay upright 30 min after → prevents esophagitis.

  • Avoid dairy, antacids, iron (↓ absorption).

  • Oral contraceptive failure → backup contraception.

6. Sulfonamides (TMP-SMX, “sulfa-”)

• MOA: blocks folic acid synthesis.

• Risks:

  • Photosensitivity.

  • Crystalluria/kidney stones → drink 2–3 L/day.

  • Folic acid deficiency → take folic acid supplement.

• Not pregnancy safe.

• Cross-sensitivity: glyburide, thiazides, loop diuretics.

7. Fluoroquinolones (-floxacin)

• Example: levofloxacin, ciprofloxacin.

• Risks:

  • Photosensitivity.

  • Achilles tendon rupture → report calf pain.

• NOT nephrotoxic (don’t confuse with aminoglycosides/vancomycin).

• Avoid calcium, iron, antacids (↓ absorption).

8. Metronidazole (Flagyl)

• Indications: C. diff, trichomoniasis (STI).

• Avoid alcohol (during & 3 days after) → violent vomiting.

• Side effects: metallic taste, dark urine (normal).

• Serious: rash, skin peeling → Stevens-Johnson syndrome → report.

9. Phenazopyridine (Pyridium)

• NOT antibiotic → urinary analgesic.

• Turns urine/body fluids orange-red (normal).

• Risks: liver toxicity (jaundice, yellow sclera).

• Patient teaching:

  • Wear pads (stains clothes).

  • Use glasses (stains contacts).

NCLEX Pearls

• Finish all antibiotics – never stop early.

• Assess allergies before giving penicillins/cephalosporins.

• Kidney distress labs:

  • Creatinine >1.3 = bad kidney.

  • BUN >20 = bad kidney.

  • Urine <30 mL/hr = kidney distress.

• Epi for anaphylaxis (EPI mnemonic):

  • E = edema (angioedema)

  • P = pruritus (hives)

  • I = inspiratory/expiratory wheezes