Antibiotics are among the most frequently prescribed drugs in the US. What most people don't realize is that because drug companies generally do not make much profit by developing oral antibiotics, there are few new options available. That's why it's especially important that the available drugs be used correctly. Taking the wrong antibiotic can allow infections to linger and sometimes become life-threatening. What you need to know…

When To Take An Antibiotic

The immune system in healthy adults is very effective at eliminating minor infections-even ones caused by bacteria. Antibiotics are needed only when an infection overwhelms the immune system's ability to stop it or when an infection is too dangerous (or too painful to be allowed to clear up on its own.

Examples: A bacterial infection of the lungs can be fatal, so it is almost always treated with antibiotics. Bacterial ear infections generally will go away without treatment, but antibiotics may decrease the duration of symptoms.

Good rule of thumb: Most infections of the ears, sinuses and respiratory tract are viral and don't require antibiotics.

How to tell: Viral infections of the respiratory tract usually start to improve in five to seven days. If you get worse after that time, there's a good chance that the infection is bacterial and may require antibiotics.

Should You Get A Culture?

Doctors usually can guess which organism is causing an infection and choose the right antibiotic-just by reviewing a patient's description of his/her symptoms.

However, cultures (taken from a throat swab, for example) should be used when it's unclear what's causing an infection-or when previous antibiotics weren't effective. In otherwise healthy adults, antibiotics start to ease symptoms of an infection within 24 hours. Symptoms that don't improve within two days may indicate an incorrect initial diagnosis or antibiotic choice.

Beware Of Side Effects

Nearly every antibiotic may cause diarrhea, intestinal cramps or yeast infections in the mouth or vagina. That's because the drugs not only kill harmful microbes, but also reduce the numbers of "good" bacteria that keep harmful bacteria and fungi in check.

Besides the general side effects, each antibiotic also has other risks. For example…

  • Amoxicillin plus clavulanate (Augmentin), commonly used for certain respiratory tract infections, may cause skin rashes and hives.
  • Doxycycline (Doryx), for chronic eye infections and Lyme disease, increases sensitivity to sunlight.
  • Ciprofloxacin (Cipro), for urinary tract infections, can cause headache, abdominal pain and vomiting.

What To Take For Common Infections

Most effective antibiotics for common medical conditions…

  • Bacterial pneumonia. Most cases are caused by an organism called Streptococcus pneumoniae, but some patients are infected with multiple and/or "resistant organisms.

Main treatment: Hospitalized patients with community-acquired pneumonia usually are given an intravenous antibiotic, such as ceftriaxone (Rocephin) with azithromycin (Zithromax), or a "respiratory" fluoroquinolone, such as levofloxacin (Levaquin).

  • Ear infections. Even doctors have difficulty differentiating viral from bacterial ear infections. Antibiotics often are used "just in case." If the infection is bacterial, the symptoms will start to abate within 24 hours of starting an antibiotic.

Main treatment: Amoxicillin for seven to 10 days. Patients with a history of antibiotic use for ear infections may have resistant organisms and will probably be given a broad-spectrum cephalosporin antibiotic, such as cefdinir (Omnicef). Similarly, patients who are allergic to amoxicillin may be given a cephalosporin antibiotic if the allergy is mild-or a fluoroquinolone, such as levofloxacin, if the allergy is severe.

  • Sinus infections. Recent research by the Cochrane Collaboration, which reviews healthcare practices and research evidence, found that about 80% of patients with sinus infections recover within two weeks without antibiotics.

However, a viral sinus infection can sometimes progress to a more serious, secondary bacterial infection. Patients with sinus pain that lasts for more than a week to 10 days-or who have a period of recovery followed by a painful relapse-probably need antibiotics.

Main treatment: The same as that used for ear infections.

  • Skin infections are usually due to Staphylococcus aureus or Streptococcus pyogenes, common bacteria that can enter the skin through a cut or scrape.

Recent danger: A virulent, drug-resistant form of staph, known as methicillin-resistant Staphylococcus aureus (MRSA), can cause cellulitis, a life-threatening infection even in healthy adults.

What to look for: Although most localized skin infections will clear up on their own, an area of skin that is red and feels warm and tender and might spread rapidly could be cellulitis. In severe cases, the center area will turn black as the tissue degenerates. Treatment of MRSA usually requires consultation with an infectious disease specialist.

  • Urinary tract infections (UTIS) usually occur when fecal bacteria enter the urethra. Women get UTIs more often than men because of the close proximity of the urethra to the anus.

Mild UTIs often will clear up on their own In studies, about two-thirds of women who take a placebo will recover within seven to 10 days, compared with 80% to 85% of those taking antibiotics. However, antibiotics are usually recommended both for symptom relief and to prevent a UTI from progressing to pyelonephritis, a dangerous kidney infection.

Main treatment: Trimethoprim plus sulfamethoxazole (Septra or Bactrim), a combination treatment usually taken for three days.

Important: If you get two or more UTIs a year, you may have resistant organisms. Your doctor may perform a urine culture to identify the organism, which will determine the appropriate antibiotic.

Caution: Don't combine ciprofloxacin with antacids or iron supplements—both can interfere with the absorption of this antibiotic.

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