Facts on File Encyclopedia of Health and Medicine

COMMON ANTIBIOTIC MEDICATIONS

Aminoglycosides
gentamicin neomycin tobramycin

Cephalosporins
cefaclor cefadroxil cefepime
cefdinir cefoperazone cefoxitin
cefprozil cefprozil ceftazidime
cefuroxime cephalexin cephradine
loracarbef

Macrolides
azithromycin clarithromycin erythromycin

Quinolones (Fluoroquinolones)
cinoxacin ciprofloxacin enoxacin
gatifloxacin levofloxacin lomefloxacin
moxifloxacin nalidixic acid norfloxacin
ofloxacin sparfloxacin trovafloxacin

Penicillins
amoxicillin amoxicillin/ penicillin V
clavulanate potassium

Sulfonamides
cotrimoxazole trimethoprim trimethoprim/
sulfamethoxazole

Tetracyclines
doxycycline minocycline tetracycline

How These Medications Work

Antibiotics are either bacteriocidal (kill bacteria
directly) or bacteriostatic (kill bacteria by prevent-
ing them from reproducing). Some antibiotics are
effective against anaerobic bacteria (bacteria that
thrive in low-oxygen environments) and others
against aerobic bacteria (bacteria that require nor-
mal atmospheric oxygen concentrations to sur-
vive). Just as the strains of bacteria share common
traits yet have distinguishing features, the antibi-
otics within a particular class have similarities and
differences. Doctors match bacteria and antibiotic
for greatest EFFICACY. Individual variations among
people also influence antibiotic effectiveness.

Therapeutic Applications
Antibiotic medications are effective for treating
bacterial infections. They have no effect on viral

infections or fungal infections. Laboratory analysis

of fluid or tissue samples, called culture and sensi-

tivity, is usually necessary to determine whether

an infection is bacterial. The analysis involves

attempting to grow the bacteria in the laboratory,

then determining which antibiotics can kill the

bacteria. Types of bacteria are sensitive to specific

classes of antibiotics, so knowing the general clas-

sification of the bacteria is generally sufficient for

the doctor to prescribe an antibiotic medication

that will kill it.

Risks and Side Effects

Antibiotic medications have numerous side

effects, ranging from HYPERSENSITIVITY REACTION

(allergy) to LIVERor kidney damage. Allergy to

penicillin is the most common DRUGallergy. Some

antibiotics diminish the effectiveness of oral con-

traceptives (birth control pills). Most antibiotics

increase the possibility for fungal (yeast) infection

because they disturb the balance of NORMAL FLORA.

Common consequences of this effect are antibi-

otic-related DIARRHEAand oral or vaginal CANDIDIA-

SIS(yeast infection of the mouth or vagina).

ANTIBIOTIC RESISTANCE is a significant concern.

Numerous strains of bacteria have adapted to

become resistant to the antibiotics commonly used

to treat the infections they cause. Factors that con-

tribute to antibiotic resistance include overpre-

scribing of antibiotics and failure to take antibiotic

medications for the full course of prescribed treat-

ment. These factors expose bacteria to antibiotics

without killing them, giving the bacteria opportu-

nity to adapt in ways that block the actions of the

antibiotics in future generations of the bacterial

strain. It is essential to take antibiotic medications

only when necessary and for the full course of

treatment.

See also ANTIBIOTIC PROPHYLAXIS;ANTIFUNGAL MED-

ICATIONS; ANTIVIRAL MEDICATIONS.

antifungal medications Drugs that kill fungi

(yeast). Antifungal medications are available for

topical or systemic treatment. Some fungal infec-

tions require both. Antifungal medications work

through various mechanisms to interfere with the

ability of fungi to survive or reproduce. Broad-

spectrum antifungal medications are effective for

treating a variety of fungal infections; narrow-

308 Infectious Diseases