Cephalosporins have a mechanism of action identical to that
of the penicillins. However, the basic chemical structure of the penicillins
and cephalosporins differs in other respects, resulting in some difference in the
spectrum of antibacterial activity. Like the penicillins, cephalosporins have a
beta-lactam ring structure that interferes with synthesis of the bacterial cell
wall and so are bactericidal. Cephalosporins are derived from cephalosporin C
which is produced from Cephalosporium acremonium.
Cephalosporins are used to treat pneumonia, strep throat,
staph infections, tonsillitis, bronchitis, otitis media, various types of skin
infections, gonorrhea, urinary tract infections Cephalosporin antibiotics are
also commonly used for surgical prophylaxis. Cephalexin can also be used to
treat bone infections.
Cephalosporins are among the most diverse classes of
antibiotics, they are grouped into "generations" by their
antimicrobial properties. Each newer generation has a broader spectrum of
activity than the one before.
·
The first generation
cephalosporins include: Their spectrums of activity are quite similar. They
possess generally excellent coverage against most gram-positive pathogens and
variable to poor coverage against most gram negative pathogens. The first
generation includes:
o
cephalothin
o
cefazolin
o
cephapirin
o
cephradine
o
cefadroxil
·
The second generation
cephalosporins. In addition to the gram positive spectrum of the first
generation cephalosporins, these agents have expanded gram negative spectrum.
Cefoxitin and cefotetan also have good activity against Bacteroides fragilis.
Enough variation exists between the second generation cephalosporins in regard
to their spectrums of activity against most species of gram negative bacteria,
that susceptibility testing is generally required to determine sensitivity. The
second generation includes:
o
cefaclor
o
cefamandole
o
cefonicid
o
ceforanide
·
The third generation
cephalosporins have much expanded gram negative activity. However, some members
of this group have decreased activity against gram-positive organisms. They
have the advantage of convenient administration, but they are expensive. The
third generation includes:
o
cefcapene
o
cefdaloxime
o
cefditoren
o
cefetamet
o
cefixime
o
cefmenoxime
o
cefodizime
o
cefoperazone
o
cefotaxime
o
cefpimizole
o
cefpodoxime
o
ceftibuten
o
ceftriaxone
·
The 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 fourth generation cephalosporins can cross blood brain barrier and are
effective in meningitis. The fourth generation includes:
o
cefclidine
o
cefepime
o
cefluprenam
o
cefozopran
o
cefpirome
o
cefquinome
Cephalosporins side effects
Cephalosporins generally cause few side effects. Common side
effects associated these drugs include: diarrhoea, nausea, mild stomach cramps
or upset. Approximately 5–10% of patients with allergic hypersensitivity to
penicillins will also have cross-reactivity with cephalosporins. Thus,
cephalosporin antibiotics are contraindicated in people with a history of
allergic reactions (urticaria, anaphylaxis, interstitial nephritis, etc) to
penicillins or cephalosporins. Cephalosporin antibiotics are classed as
pregnancy category B.
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