Cephalosporins

Pharmacology Outline

Cephalosporins and generations 1-4

Diana Crane RN

Karen Daniels RN

Cephalosporins: In 1948 a fungus was discovered that was found to be active against gram positive and negative bacteria as well as resistant to beta –lactamase.  This Beta-lactam structure inhibits the enzyme necessary for cell wall synthesis, this leads to cell wall lysis, and cell death.  .  The beta-lactamases can destroy some forms of cephalosporins.  Cephalosporins have been altered to treat wider ranges of bacterium, and have grown to encompass four groups or generations.  Cephalosporins are used widely in healthcare.  Most forms of cephalosporins are used IV or IM, few are given PO.  They are protein bound and largely excreted unchanged in the urine. 

First Generation: Destroyed by beta-lactamases.  Effective against most gram positive and gram negative bacteria.  Examples of first generation cephalosporins are cefadroxil, cefazolin, cephalexin, and cephradine.  These antibiotics are used to treat infections including UTI, beta-hemolytic streptococcal infections, staphylococcal skin infections, otitis media, and bone infections. 

Second Generation: Some are affected by beta-lactamases.  Effective against most gram positive and gram negative bacteria.  Second generation is effective against more gram negative bacteria than first generation, and is also effective against some anaerobes.  Examples of second generation cephalosporins include cefaclor, cefotetan, cefoxitin, and cefuroxime.  These are used to treat infections including  septicemia, staphylococcus aureus, meningitis, and surgical prophylaxis. 

Third Generation:  Resistant to beta-lactamases.  Effective against fewer gram positive bacteria than first and second generations.  Effective against increased number of gram negative bacteria.  Examples of third generation cephalosporins include cefdinir, cefixime, cefpodoxime, and ceftazidime.  These are used to treat infections, including acute sinusitis, chronic bronchitis, Streptococcus pyogenes, Neisserie gonorrhoeae, Haemophilus influenza, and respiratory infections.  Cefditoren is safe to use with oral birth control. 

Fourth Generation:  resistant to beta-lactimases.  Broader gram positive effectiveness than third generation.  Resistant to most beta-lactamase bacteria.   An example of a fourth generation cephalosporin is cefepime which is effective in treating pneumonia, E. coli, Klebsiella, Proteus, and has broader gram positive coverage than third generation cephalosporins. 

Pharmokinetics:  Most given IM or IV, few PO options.  Protein bound.  60-80% excreted in urine.

Pharmodynamics:  Inhibit cell wall synthesis, causing cell lysis and cell death.  Onset of action is nearly immediate for IV, 30-60 minutes for PO. 

Side Effects:  GI disturbances such as nausea, vomiting and diarrhea.  Blood clotting time can be increased, causing increased bleeding.  Nephrotoxicity, when large doses are used, and when pt. has renal disorders.  Proteinuria, glycosuria, renal failure, nephrotoxicity.  . 

Drug interactions: When given with probenecid urine excretion of cephalosporins is decreased, Action of drug is increased.  Tetracycline or erythromycin can decrease effectiveness of cephalosporins.    Uricosuric medications can interfere with excretion of cephalosporins. 

Herbal interactions:  Do not use acidophilus, separate doses by several hours.  Angelica, anise, arnica, chamomile, clove, celery, garlic, ginger, ginseng, ginkgo and others can increase bleeding risk. 

Food interactions:  Do not use alcohol while using cephalosporins, this may cause dizziness, cramping, nausea and vomiting. 

Nursing considerations: Assess for allergies or sensitivities to PCN, and type of reaction.  Check laboratory studies, especially AST, ALT, BUN, and Creatine.  Bowel pattern, especially for diarrhea.  Bleeding risk, especially if pt. is on anticoagulants.  Nephrotoxicity, I & O.  If GI upset, give with food. 

Teaching: Teach patient signs of anaphylaxis, difficulty breathing or swallowing, hives, wheezing, and what to do incase these are evident.  To report to Doctor if increased bleeding occurs.  To take with food to decrease GI discomfort.  To eat yogurt or buttermilk to decrease chances of diarrhea and yeast infection.  Teach patient to finish full course of treatment, even if they feel well.  Teach patient the importance of discussing all other medications, and herbal supplements with prescribing Doctor.  Teach pt. to report diarrhea, or decreased urine output.   Teach pt. to report if infection symptoms are increasing or not decreasing while on antibiotic.  

References:

AHFS Consumer Medication Information. Bethesda (MD): American Society of Health-System Pharmacists, Inc. (2008). Cephalexin retrieved from http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682733.html

 

Kee, J. L., Hayes, E. R., & McCuistion, L. E. (2012). Pharmacology: A nursing process approach. St. Louis, MO: Elsevier.

Skidmore-Roth, L. (2008). Mosby's nursing drug reference. St. Louis, MO: Elsevier.