ARTICLES
Antibiotics And Their Types, Uses, And Side Effects
An antibiotic is a drug that kills or slows the growth of
bacteria. Antibiotics are one class of antimicrobials, a
larger group which also includes anti-viral, anti-fungal,
and anti-parasitic drugs. Antibiotics are chemicals produced
by or derived from microorganisms (i.e. bugs or germs such
as bacteria and fungi). The first antibiotic was discovered
by Alexander Fleming in 1928 in a significant breakthrough
for medical science.
Antibiotics are among the most frequently prescribed medications
in modern medicine. Some antibiotics are 'bactericidal',
meaning that they work by killing bacteria. Other antibiotics
are 'bacteriostatic', meaning that they work by stopping
bacteria multiplying.
Each different type of antibiotic affects different bacteria
in different ways. For example, an antibiotic might inhibit
a bacterium's ability to turn glucose into energy, or its
ability to construct its cell wall. When this happens, the
bacterium dies instead of reproducing.
Some antibiotics can be used to treat a wide range of infections
and are known as 'broad-spectrum' antibiotics. Others are
only effective against a few types of bacteria and are called
'narrow-spectrum' antibiotics.
Side effects of antibiotics
Antibiotics can literally save lives and are effective in
treating illnesses caused by bacterial infections. However,
like all drugs, they have the potential to cause unwanted
side effects. Many of these side effects are not dangerous,
although they can make life miserable while the drug is being
taken.
In general, antibiotics rarely cause serious side effects.
The most common side effects from antibiotics are diarrhea,
nausea, vomiting. Fungal infections of the mouth, digestive
tract and vagina can also occur with antibiotics because
they destroy the protective 'good' bacteria in the body (which
help prevent overgrowth of any one organism), as well as
the 'bad' ones, responsible for the infection being treated.
Some people are allergic to antibiotics, particularly penicillins.
Allergic reactions cause swelling of the face, itching and
a skin rash and, in severe cases, breathing difficulties.
Allergic reactions require prompt treatment.
Types of antibiotics
There are many different kinds of antibiotics. The type
of antibiotics you take depends on the type of infection
you have and what kind of antibiotics are known to be effective.
The main classes of antibiotics:
Aminoglycosides
Cephalosporins
Fluoroquinolones
Macrolides
Penicillins
Tetracyclines
Macrolides
There are a couple of new relatives of erythromycin (azithromycin
and clarithromycin) that work the same way, but kill more
bugs and have slightly fewer side effects. The erythromycin-like
antibiotics are also known as macrolides. Macrolides belong
to the polyketide class of natural products. Macrolide antibiotics
are used to treat respiratory tract infections, genital,
gastrointestinal tract, soft tissue infections caused by
susceptible strains of specific bacteria.
Macrolides bind with ribosomes from susceptible bacteria
to prevent protein production. This action is mainly bacteriostatic,
but can also be bactericidal in high concentrations.
Macrolides cause very little allergy problems compared to
the penicillins and cephalosporins, the biggest concern with
these medicines is that they can irritate the stomach.
The most commonly-prescribed macrolides:
erythromycin
clarithromycin
azithromycin
roxithromycin
Aminoglycosides
Aminoglycoside antibiotics are used to treat infections
caused by gram-negative bacteria. Aminoglycosides may be
used along with penicillins or cephalosporins to give a two-pronged
attack on the bacteria. Aminoglycosides work quite well,
but bacteria can become resistant to them. Since aminoglycosides
are broken down easily in the stomach, they can't be given
by mouth and must be injected. When injected, their side
effects include possible damage to the ears and to the kidneys.
This can be minimized by checking the amount of the drug
in the blood and adjusting the dose so that there is enough
drug to kill bacteria but not too much of it. Generally,
aminoglycosides are given for short time periods.
The aminoglycosides are drugs which stop bacteria from making
proteins. This effect is bactericidal.
The most commonly-prescribed aminoglycosides:
amikacin
gentamicin
kanamycin
neomycin
streptomycin
tobramycin
Cephalosporins
Cephalosporins are grouped into "generations" by
their antimicrobial properties. Cephalosporins are categorized
chronically, and are therefore divided into first, second,
and third generations. Currently, three generations of cephalosporins
are recognized and a fourth has been proposed. Each newer
generation of cephalosporins has greater gram negative antimicrobial
properties than the preceding generation. The later-generation
cephalosporins have greater effect against resistant bacteria.
Cephalosporins are used to treat pneumonia, strep throat,
staph infections, tonsillitis, bronchitis, otitis media,
various types of skin infections, gonorrhea. Cephalosporin
antibiotics are also commonly used for surgical prophylaxis.
Cephalosporins are closely related to the penicillins.
Cephalosporins have a bacteriocidal effect by inhibiting
the synthesis of the bacteria cell wall.
The most commonly-prescribed cephalosporins:
First generation
o cephazolin
o cefadroxil
o cephalexin
o cephradine
Second generation
o cefaclor
o cefuroxime
o cefprozil
o loracarbef
Third generation
o cefotaxime
o cefixime
o cefpodoxime
o ceftazidime
o cefdinir
Fourth generation
o cefepime
o cefpirome
Fluoroquinolones
Fluoroquinolones are known as broad-spectrum antibiotics,
meaning they are effective against many bacteria. Fluoroquinolones
are used to treat most common urinary tract infections, skin
infections, and respiratory infections (such as sinusitis,
pneumonia, bronchitis). Common side effects of fluoroquinolones
include mainly the digestive system: mild stomach pain or
upset, nausea, vomiting, and diarrhea. These are usually
mild and go away over time. Fluoroquinolones should not be
given during pregnancy.
Fluoroquinolones inhibit bacteria by interfering with their
ability to make DNA. This activity makes it difficult for
bacteria to multiply. This effect is bacteriocidal.
The most commonly-prescribed fluoroquinolones:
ciprofloxacin
gatifloxacin
gemifloxacin
levofloxacin
moxifloxacin
norfloxacin
ofloxacin
trovafloxacin
Penicillins
Penicillin was the first antibiotic discovered by Alexander
Fleming in 1929. Penicillins are used to treat skin infections,
dental infections, ear infections, respiratory tract infections,
urinary tract infections, gonorrhea. Penicillins are sometimes
combined with other ingredients called beta-lactamase inhibitors,
which protect the penicillin from bacterial enzymes that
may destroy it before it can do its work.
Penicillins are usually very safe. The greatest risk is
an allergic reaction, which can be severe. People who have
been allergic to cephalosporins are likely to be allergic
to penicillins.
Penicillins block the construction of bacteria cell walls,
causing the walls to break down, and eventually killing the
bacteria.
The most commonly-prescribed penicillins:
amoxicillin
ampicillin
bacampicillin
oxacillin
penicillin
Tetracyclines
Tetracyclines are a family of antibiotics used to treat
a broad spectrum of bacterial infections. Tetracyclines were
discovered in the late 1940s and were extremely popular when
they were first discovered. The tetracycline antibiotics
have a very broad spectrum of action.
Tetracyclines are used to treat mild acne, Rocky Mountain
spotted fever, Lyme Disease, upper respiratory tract infections,
urinary tract infections, sexually transmitted diseases,
typhus.
The most commonly-prescribed tetracyclines:
tetracycline
doxycycline
minocycline
Antibiotic resistance
Antibiotics are extremely important in medicine, but unfortunately
bacteria are capable of developing resistance to them. Antibiotic-resistant
bacteria are germs that are not killed by commonly used antibiotics.
When bacteria are exposed to the same antibiotics over and
over, the bacteria can change and are no longer affected
by the drug.
Bacteria have number of ways how they become antibiotic-resistant.
For example, they possess an internal mechanism of changing
their structure so the antibiotic no longer works, they develop
ways to inactivate or neutralize the antibiotic. Also bacteria
can transfer the genes coding for antibiotic resistance between
them, making it possible for bacteria never exposed to an
antibiotic to acquire resistance from those which have. The
problem of antibiotic resistance is worsened when antibiotics
are used to treat disorders in which they have no efficacy
(e.g. antibiotics are not effective against infections caused
by viruses), and when they are used widely as prophylaxis
rather than treatment.
Resistance to antibiotics poses a serious and growing problem,
because some infectious diseases are becoming more difficult
to treat. Resistant bacteria do not respond to the antibiotics
and continue to cause infection. Some of these resistant
bacteria can be treated with more powerful medicines, but
there some infections that are difficult to cure even with
new or experimental drugs. |