Medicine & USMLE


Anti-Infective Drugs
  1. Vancomycin
  2. Metronidazole
  3. Penicillins
  4. Cephalosporins
  5. Macrolides
  6. Fluoroquinolones
  7. Aminoglycosides
  8. Tetracyclines
  9. Sulfonamides
  10. Rifampin
  11. Isoniazid
  12. Ethambutol
  13. Chloroquine
  14. Acyclovir
  15. Oseltamivir
  16. Azoles
  17. Nystatin
  18. Amphotericin B


Penicillins are antibiotics used to treat a wide variety of bacterial infections. The biggest worry with penicillin is an anaphylactic reaction, so the nurse should monitor for signs of an allergic reaction like hives, rashes, itching, and difficulty breathing. Penicillins and cephalosporins have a cross sensitivity, so the severity of the allergy should be determined before giving the medication.

Key Points

  • Penicillins 
    • Key Drugs “-cillin”
      • Penicillin
      • Amoxicillin
      • Ampicillin
      • Piperacillin-tazobactam
    • Mechanism of Action
      • Antibiotic
        • Weakens/destroys the bacterial cell wall
        • Different types of penicillin will be given based on whether the bacterial infection is gram negative, gram positive, or unknown
      • First antibiotic made for clinical use
    • Clinical Use
      • Treatment of infections
        • Respiratory infections - Pharyngitis, Tonsillitis, etc.
        • Meningitis
        • Endocarditis
        • Otitis media
        • Urinary tract infections
      • Prophylactic treatment
    • Side Effects and Adverse Reactions
      • Allergy/Anaphylaxis
        • Occurs more with penicillins than with any other drug
        • Cross-sensitivity with cephalosporins
          • Determine severity of allergy before giving penicillins to a patient who is allergic to cephalosporins, and vice versa.
        • Instruct patients to report any sign of allergy, such as dyspnea, skin rash, hives, and itching.
        • A skin test may be given prior to administration, where a small amount of allergen is injected intradermally, and the patient is monitored for a local allergic reaction. When performing a skin test, the nurse must have epinephrine and respiratory support readily available.
      • C. Diff Overgrowth / Superinfection
        • Penicillin antibiotics can disturb normal gut flora, leading to overgrowth and pathogenicity of species like C. Diff
      • Oral contraceptives may become less ineffective
        • Ampicillin and amoxicillin have been shown to be correlated with an increase in unwanted pregnancies
        • Women of childbearing age should be advised to use other methods of contraception
      • GI upset (nausea, vomiting, diarrhea)
        • Penicillins should be taken on an empty stomach, with the exception of amoxicillin which may be taken with food to decrease GI upset
      • Bleeding
        • Secondary to disrupted platelet function
        • Monitor platelet count
      • Drug Toxicity
        • Risk is increased with use of NSAIDS. The NSAID will displace the penicillin from the protein binding sites, creating an increase of free drug in the blood
        • Use with caution in patients with kidney disease, as the drug won’t be excreted as quickly and can cause penicillins to reach toxic levels