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Cephalosporin Antibiotics Cephalosporins
are the most frequently prescribed class of antibiotics.
Cephalosporins are bactericidal agents, which means
that they kill bacteria. They have the same mode
of action as as penicillins. All bacterial cells
have a cell wall that protects them. Cephalosporins
disrupt the synthesis of the peptidoglycan layer
of bacterial cell walls, which causes the walls to
break down and eventually the bacteria die.
Cephalosporin compounds were first isolated from
cultures of Cephalosporium acremonium from a sewer
in Sardinia in 1948 by Italian scientist Giuseppe
Brotzu. The first agent cephalothin (cefalotin) was
launched by Eli Lilly in 1964.
Cephalosporins are used to treat a wide variety
of bacterial infections, such as respiratory tract
infections (pneumonia, strep throat, tonsillitis,
bronchitis), skin infections and urinary tract infections.
They are sometimes given with other antibiotics.
Cephalosporins are also commonly used for surgical
prophylaxis - prevention of bacterial infection before,
during, and after surgery.
Classification of Cephalosporins
Cephalosporins are grouped into "generations" based
on their spectrum of antimicrobial activity. The
first cephalosporins were designated first generation
while later, more extended spectrum cephalosporins
were classified as second generation cephalosporins.
Each newer generation has significantly greater gram-negative
antimicrobial properties than the preceding generation,
in most cases with decreased activity against gram-positive
organisms. Fourth generation cephalosporins, however,
have true broad spectrum activity.
First generation
First generation cephalosporins are moderate spectrum
agents. They are effective alternatives for treating
staphylococcal and streptococcal infections and therefore
are alternatives for skin and soft-tissue infections,
as well as for streptococcal pharyngitis.
The first generation cephalosporins are Cefadroxil,
Cephalexin, Cephaloridine, Cephalothin, Cephapirin,
Cefazolin, and Cephradine. Cefazolin is the most
commonly used first generation cephalosporin. The
others have similar efficacy to Cephalexin, but must
be dosed more often, and are therefore not as commonly
prescribed.
Second generation
The second generation cephalosporins have a greater
gram-negative spectrum while retaining some activity
against gram-positive bacteria. They are useful agents
for treating upper and lower respiratory tract infections,
sinusitis and otitis media. These agents are also
active against E. coli, Klebsiella and Proteus, which
makes them potential alternatives for treating urinary
tract infections caused by these organisms.
The second generation cephalosporins are Cefaclor,
Cefoxitin, Cefprozil, Cefuroxime.
Third generation
Third generation cephalosporins have a broad spectrum
of activity and further increased activity against
gram-negative organisms. Some members of this group
(particularly those available in an oral formulation)
have decreased activity against gram-positive organisms.
The parenteral third generation cephalosporins (ceftriaxone
and cefotaxime) have excellent activity against most
strains of Streptococcus pneumoniae, including the
vast majority of those with intermediate and high
level resistance to penicillin. These agents also
have activity against N. gonorrhoeae. Ceftazidime
has useful antipseudomonal activity.
The third generation cephalosporins are Cefdinir,
Cefixime, Cefpodoxime, Ceftibuten, Ceftriaxone, Cefotaxime.
Fourth generation
Fourth generation cephalosporins are extended spectrum
agents with similar activity against gram-positive
organisms as first generation cephalosporins. They
also have a greater resistance to beta-lactamases
than the third generation cephalosporins. Many can
cross blood brain barrier and are effective in meningitis.
The fourth generation cephalosporins are Cefepime,
Cefluprenam, Cefozopran, Cefpirome, Cefquinome.
Cefepime is a more gram-negative drug with somewhat
enhanced activity against pseudomonas but slightly
lesser activity against pneumococci. Cefpirome is
more active against pneumococci and has somewhat
lesser activity against pseudomonas. These drugs
also have activity against nosocomial pathogens such
as Enterobacter and Acinetobacter and their use should
therefore be restricted to the setting of nosocomial
sepsis.
Side effects
Cephalosporins generally cause few side effects.
Common side effects involve mainly the digestive
system: stomach cramps or upset, nausea, vomiting,
and diarrhea. These side effects are usually mild
and go away over time. Cephalosporins can sometimes
cause overgrowth of fungus normally present in the
body. This overgrowth can cause mild side effects
such as a sore tongue, sores inside the mouth, or
vaginal yeast infections.
More serious but infrequent reactions that can sometimes
occur with cephalosporins include: black, tarry stools;
chest pain; fever; painful or difficult urination;
allergic reactions; serious colitis. Serious colitis
is a rare side effect that includes severe watery
diarrhea (sometimes containing blood or mucus), severe
stomach cramps, fever, and weakness or faintness.
Because the cephalosporins are structurally similar
to the penicillins, some patients allergic to penicillins
may be allergic to a cephalosporin antibiotic. The
incidence of cross-sensitivity is approximately 5c10%. |
