Cephalosporins

The effectiveness of penicillin in the treatment of infections prompted research directed toward finding new antibiotics with a wider range of antibacterial activity. The cephalosporins are a valuable group of drugs that are effective in the treatment of almost all of the strains of bacteria affected by the penicillins, as well as some strains of bacteria that have become resistant to penicillin.

The cephalosporins are structurally and chemically related to penicillin. The cephalosporins are divided into first-, second-, and third-generation drugs. Particular cephalosporins also may
be differentiated within each group according to the microorganisms that are sensitive to them. Generally, progression from the first-generation to the second-generation and then to the third-generation drugs shows an increase in the sensitivity of gram-negative microorganisms and a
decrease in the sensitivity of gram-positive microorganisms. For example, a first-generation cephalosporin would have more use against gram-positive microorganisms than would a third generation cephalosporin. This scheme of classification is becoming less clearly defined as newer drugs are introduced.

First-Generation Cephalosporins

1 cefadroxil
2 cefazolin sodium
3 cephalexin

Second-Generation Cephalosporins

1 cefaclor
2 cefamandole
3 cefotetan
4 cefoxitin
5 cefpodoxime
6 cefprozil
7 cefuroxime
8 loracarbef

Third-Generation Cephalosporins

1 cefdinir
2 cefepime hydrochloride
3 cefixime
4 cefoperazone
5 cefotaxime
6 ceftazidime
7 ceftibuten hydrochloride
8 ceftizoxime
9 ceftriaxone

ACTIONS

Cephalosporins affect the bacterial cell wall, making it defective and unstable. This action is similar to the action of penicillin. The cephalosporins are usually bactericidal (capable of destroying bacteria).

USES

The cephalosporins are used in the treatment of infections caused by susceptible microorganisms. Examples of microorganisms that may be susceptible to the cephalosporins include streptococci, staphylococci,citrobacters, gonococci, shigella, and clostridia. Culture and sensitivity tests are performed whenever possible to determine which antibiotic, including a cephalosporin, will best control an infection caused by a specific strain of bacteria. Pharyngitis, tonsillitis, otitis media, lower respiratory infections, urinary tract infections, septicemia, and gonorrhea are examples of the types of infections that may be treated with the cephalosporins.

The cephalosporins also may be used perioperatively, that is, during the preoperative, intraoperative, and postoperative periods, to prevent infection in patients having surgery on a contaminated or potentially contaminated area, such as the gastrointestinal tract or vagina. In some instances, a specific drug may be recommended for postoperative prophylactic use only.

ADVERSE REACTIONS

The most common adverse reactions seen with administration of the cephalosporins are gastrointestinal disturbances, such as nausea, vomiting, and diarrhea.

Hypersensitivity (allergic) reactions may occur with administration of the cephalosporins and range from mild to life threatening. Mild hypersensitivity reactions include pruritus, urticaria, and skin rashes. More serious hypersensitivity reactions include Stevens- Johnson syndrome (fever, cough, muscular aches and pains, headache, and the appearance of lesions on the
skin, mucous membranes, and eyes), hepatic and renal dysfunction, aplastic anemia (anemia due to deficient red blood cell production), and epidermal necrolysis (death of the epidermal layer of the skin).

Because of the close relation of the cephalosporins to penicillin, a patient allergic to penicillin also may be allergic to the cephalosporins.

Other adverse reactions that may be seen with administration of the cephalosporins are headache,
dizziness, nephrotoxicity (damage to the kidneys by a toxic substance), malaise, heartburn, and fever. Intramuscular (IM) administration often results in pain, tenderness, and inflammation at the injection site. Intravenous (IV) administration has resulted in thrombophlebitis and phlebitis.

Therapy with cephalosporins may result in a bacterial or fungal superinfection. Diarrhea may be an indication of pseudomembranous colitis, which is one type of bacterial superinfection.

CONTRAINDICATIONS

The nurse should not administer cephalosporins if the patient has a history of allergies to cephalosporins or penicillins.

PRECAUTIONS

The nurse should use cephalosporins cautiously in patients with renal or hepatic impairment and in patients with bleeding disorders. Safety of cephalosporin administration has not been established in pregnancy or lactation; these drugs are assigned to Pregnancy Category B.

INTERACTIONS

The risk of nephrotoxicity increases when the cephalosporins are administered with the aminoglycosides. The risk for bleeding increases when the cephalosporins are taken with oral anticoagulants. A disulfiram-like reaction may occur if alcohol is consumed within 72 hours after cephalosporin administration. Symptoms of a disulfiram-like reactions include flushing, throbbing in the head and neck, respiratory difficulty, vomiting, sweating, chest pain, and hypotension. Severe reactions may cause arrhythmias and unconsciousness. When the cephalosporins are administered with the aminoglycosides, the risk for nephrotoxicity increases.