Medications

Dozens of antibiotics are available that can treat most cases of pneumonia in or out of the hospital, but it is sometimes difficult for the physician to select the best drug. Patients with pneumonia are given a specific antibiotic based on what type of organism is causing the disease. If the organism is unknown, the antibiotic is based on individual risk factors, such as age, health, and severity of the illness.

In determining the appropriate antibiotic, the physician must first answer a number of questions:

  • How severe is the pneumonia? Mild-to-moderate cases can be treated at home with oral antibiotics while severe pneumonia usually requires intravenous antibiotics administered in the hospital.
  • If the organism causing the pneumonia is not known, was the disorder community- or hospital-acquired? Different organisms are usually involved in each setting, and the physician can often use this information to guess the most likely organism causing the pneumonia.
  • If the organism is known, is it typical or atypical? Typical bacterial, community acquired pneumonias for example, are usually caused by Streptococcus pneumoniae, Haemophilus influenzae, or Moraxella catarrhalis, which have traditionally been treated with penicillin or other standard antibiotics. Such antibiotics, however, do not affect atypical organisms, such as Legionella, Mycoplasma, or Chlamydia. (These organisms are generally treated with a macrolide or possibly a newer quinolone.)
  • Does the patient have an impaired immune system, such as in AIDS? Antibiotics used to treat such patients may differ from those used in patients with healthy immune systems.

Once an antibiotic has been chosen, there are still difficulties:

  • Individuals respond differently to the same antibiotic depending on age, health, size, and other factors.
  • Patients can be allergic to certain antibiotics, thus requiring alternatives.
  • Patients may harbor strains of bacteria that are resistant to certain antibiotics.

Antibiotic Treatments for Community-Acquired Pneumonia

For a more detailed discussion of the different types of antibiotics, see the "Antibiotic Classes" section below.

Many cases of community-acquired pneumonia are caused by S. pneumoniae, bacteria that usually respond to antibiotics known as beta lactams (which include penicillin,) and to macrolides. However, resistant strains of S. pneumoniae are increasingly common; most resistant strains respond to newer quinolines or ketolides.

In addition, other important causes of CAP, particularly in younger people, are atypical bacteria, which respond to macrolides (erythromycin, clarithromycin, or azithromycin) or ketolides (telithromycin), or newer quinolones. Such quinolones include levofloxacin (Levaquin), gatifloxacin (Tequin), gemifloxacin (Factive), and moxifloxacin (Avelox).

Antibiotic treatment for CAP is determined by a number of factors including the patient's history of antibiotic therapy, co-existing diseases (COPD, diabetes, heart failure), and where they live(outpatient, hospital patient, nursing home resident). Treatment options can include a single drug, such as levofloxacin or doxycycline, or combination treatment, such as a macrolide administered with a beta-lactam antibiotic.

Antibiotics taken by mouth are generally sufficient for patients whose CAP is mild enough to be treated at home. Intravenous antibiotics are required for hospitalized patients with CAP.

Antibiotic Treatments for Hospital-Acquired (Nosocomial) Pneumonia

Gram-Positive Pneumonia. S. aureus is common in hospital-acquired pneumonia and is a potentially life-threatening infection. Resistance to penicillin is the rule in these cases but certain specialized penicillins such as nafcillin are often still effective. The alternatives to penicillins are first- or second generation cephalosporins. Unfortunately, resistance to these agents is increasing as well. Vancomycin is used for highly resistant bacteria.

Gram-Negative Pneumonia. Patients with hospital-acquired pneumonia are at high risk for infection from gram-negative organisms. Such organisms include Pseudomonas aeruginosa and Klebsiella pneumonia, which require aggressive specific therapy. Powerful antibiotics used against these organisms include the fourth-generation cephalosporins, carbapenems, or ciprofloxacin alone or in combination with an aminoglycides (entamicin or tobramycin). Multidrug therapy may be necessary, particularly for patients, such as those who are on mechanical ventilators, who are at very high risk for multiple dangerous organisms.

Antibiotics for P. Carinii Pneumonia (Common in HIV-Positive Patients)

Trimethoprim-sulfamethoxazole is the antibiotic combination that is the first choice for both preventing and treating P carinii pneumonia in HIV-positive patients. Clindamycin-primaquine may be a good salvage treatment for patients who do not respond to standard therapies.

Side Effects of Antibiotics

Most antibiotics have the following side effects (although specific antibiotics may have other side effects or fewer of the standard ones).

  • The most common side effect for nearly all antibiotics is stomach problems.
  • Antibiotics raise the risk for vaginal infections. Taking supplements of acidophilus or eating yogurt with active cultures may help restore healthy bacteria that offset the risk for such infections in women.
  • Allergic reactions can also occur with all antibiotics but are most common with medications derived from penicillin or sulfa. These reactions can range from mild skin rashes to rare but severe, even life-threatening anaphylactic shock.
  • Certain drugs, including some over-the-counter medications, interact with antibiotics; patients should inform the physician of all medications they are taking and of any drug allergies.

ANTIBIOTIC CLASSES

Beta-Lactams

The beta-lactam antibiotics share common chemical features. They include penicillins, cephalosporins, and some newer similar agents. They interfere with bacterial cell walls.

Penicillins. Penicillin was the first antibiotic. There are many forms to this still-important agent:

  • Natural penicillins include penicillin G (for intravenous use) and V (for oral use).
  • Penicillin derivatives called aminopenicillins, particularly amoxicillin (Amoxil, Polymox, Trimox, Wymox, or any generic formulation), are now the most common penicillins used. Amoxicillin is both inexpensive and at one time was highly effective against the S. pneumoniae bacteria. Unfortunately, bacterial resistance to amoxicillin has increased significantly, both among S. pneumoniae and H. influenzae. Ampicillin is similar, and an alternative to amoxicillin, but requires more doses and has more severe gastrointestinal side effects.
  • Amoxicillin-clavulanate (Augmentin) is an augmented penicillin that works against a wide spectrum of bacteria. An extended release form has been approved for treating adults with community-acquired pneumonia caused by bacterial strains that have become resistant to penicillin.
  • Antistaphylococcal penicillins were developed to treat Staphylococcus aureus. The standard drug was methicillin, but it is no longer used routinely because of very high rates of resistance in hospital-acquired pneumonias. Resistance in community-acquired Staphylococcus aureus is also increasing. Alternatives include vancomycin and linezolid.
  • Certain penicillins are used against Pseudomonas aeruginosa include ticarcillin and piperacillin. Piperacillin is more effective that ticarcillin.

Many people have a history of an allergic reaction to penicillin, but research has suggested that the allergy may not recur in a significant number of adults. Skin tests are available to help determine if those with a history of penicillin allergies could use these important antibiotics.

Cephalosporins. Most of these agents are not very effective against bacteria that have developed resistance to penicillin. They are classed according to their generation:

  • First generation includes cephalexin (Keflex), cefadroxil (Duricef, Ultracef), and cephradine (Velosef).
  • Second generation include cefaclor (Ceclor), cefuroxime (Ceftin), cefprozil (Cefzil), and loracarbef (Lorabid),
  • Third generation include cefpodoxime (Vantin), cefdinir (Omnicef) cefditoren (Sprectracef), cefixime (Suprax), and ceftibuten (Cedex). Ceftriaxone (Rocephin) is an injected cephalosporin. These are effective against a wide range of gram-negative bacteria.

Other Beta-Lactam Agents. Carbapenems (also known as thienamycins) include meropenem (Merrem), biapenem, faropenem, ertapenem (Invanz) and combinations (imipenem/cilastatin [Primaxin]). These agents cover a wide spectrum of bacteria. They are now used for serious hospital-acquired infection and for bacteria that have become resistant to other beta-lactam bacteria. Imipenem has serious side effects used alone so it is given in combinations with another agent, cilastatin, to offset these adverse effects. The newer agents are less toxic, although they may not be as potent.

Sanfetrinem, a novel beta-lactam antibiotic known as a trinem is proving to be effective against S. pneumoniae,H. influenzae, and M. catarrhalis.

Fluoroquinolones (Quinolones)

Fluoroquinolones (also simply called quinolones) interfere with the bacteria's genetic material so they cannot reproduce. Quinolones are not only effective against many common bacteria, but they can also be used to treat tuberculosis.

  • Ciprofloxacin (Cipro), a second-generation quinolone, remains the most potent quinolone against Pseudomonas aeruginosa bacteria. However, it is not very effective for gram-positive bacteria such as Streptococcus pneumoniae. Ofloxacin (Floxin) is generally used in drops for ear infections.
  • "Respiratory" quinolones are currently the most effective drugs available for a wide range of bacteria. Such drugs include levofloxacin (Levaquin), sparfloxacin (Zagam), gemifloxacin (Factive), and gatifloxacin (Tequin). Some of the newer fluoroquinolones only need to be taken once a day. In February 2006, Bristol-Myers Squibb notified the FDA it is changing its prescription information for Tequin (gatifloxacin). Because of reports of serious changes in blood sugar levels in vulnerable people, the company says diabetics should not use this antibiotic. In addition, the company says that elderly people, people with kidney problems, and those taking medications that affect blood sugar levels should be watched carefully while taking Tequin.
  • The fourth generation quinolones Moxifloxacin (Avelox) and clinafloxacin are proving to be effective against anaerobic bacteria.

S. pneumoniae-strains resistant to the "respiratory" quinolones are uncommon in the U.S., but resistance has dramatically increased in the past few years.

Many quinolones cause side effects, including sensitivity to light and neurologic, psychiatric, and heart problems. Pregnant women should not take these agents. The drugs also enhance the potency of oral anti-clotting agents.

Macrolides, Azalides, and Ketolides

Macrolides and azalides antibiotics also affect the genetics of bacteria. They include erythromycin, azithromycin (Zithromax, Zmax), clarithromycin (Biaxin), and roxithromycin (Rulid). These antibiotics are effective against the atypical bacteria, including Mycoplasma or Chlamydia. They are also used in some cases for S. pneumoniae and M. catarrhalis, but there is increasing bacterial resistance to these agents. Except for erythromycin they are effective against H. influenzae. Macrolide-resistance rates doubled between 1995 and 1999 as more and more children were being treated with these antibiotics. Some research is suggesting that these agents may reduce the risk for a first heart attack in some patients by reducing inflammation in the blood vessels.

Ketolides. Ketolides are a new class of antibiotic drugs. They are derived from erythromycin and were developed to combat organisms that have become resistant to macrolides. Telithromycin (Ketek), the first antibiotic in the ketolide class, was approved by the FDA in 2004 for treatment of community-acquired pneumonia (CAP).

In January 2006, the FDA issued a Public Health Advisory for healthcare providers and patients using telithromycin (Ketek). Patients treated with Ketek should stop using this antibiotic if jaundice (yellowing of the skin or whites of the eyes) develops. The FDA issued this advisory after three cases of severe liver injury in patients treated with Ketek. In June 2006, the FDA issued an advisory after 4 deaths were reported after the patients had taken the drug.

In December 2006, the FDA recommended that Ketek should not be used in patients with sinusitis or bronchitis. The FDA panel also recommended that the drug should carry a black box warning noting the potentially serious side effects, including liver failure, vision problems, loss of consciousness, and neuromuscular problems.

Early studies of Ketek did not reveal any significant risks of liver injury, compared with other antibiotics.

Tetracyclines

Tetracyclines inhibit bacterial growth. They include doxycycline, tetracycline, and minocycline. They can be effective against S. pneumoniae and M. catarrhalis, but bacteria that are resistant to penicillin are also often resistant to doxycycline. Tetracyclines' side effects include skin reactions to sunlight, possible burning in the throat, and tooth discoloration.

Aminoglycosides

Aminoglycosides (gentamicin, kanamycin, tobramycin, amikacin) are given by injection for very serious bacterial infections. They can be given only in combination with other antibiotics. Some are available in inhaled forms or by applying a solution directly to mucous membranes, skin, or body cavity. They can have very serious side effects including hearing damage, balance problems, and kidney damage.

Lincosamide

Lincosamides prevent bacteria from reproducing. The most common lincosamide is clindamycin (Cleocin). This antibiotic is useful against S. pneumoniae and S. aureus, but not against H. influenzae.

Glycopeptides

Glycopeptides (vancomycin, teicoplanin) are used for Staphylococcus aureus infections that have become resistant to standard antibiotics. The drug can be taken by mouth or given intravenously.

Trimethoprim-Sulfamethoxazole

Trimethoprim-sulfamethoxazole (Bactrim, Cotrim, Septra) is less expensive than amoxicillin. It is particularly useful for adults with mild bacterial upper respiratory infections who are allergic to penicillin. The drug is no longer effective against certain streptococcal strains. It should not be used in patients whose infections occurred after dental work or in people allergic to sulfa drugs. Allergic reactions can be very serious.

Oxazolidinone

Linezolid (Zyvox) is the first antibacterial drug in a new class of synthetic antibiotics called oxazolidinones. It has been shown to work against certain aerobic gram-positive bacteria.

Preventing and Treating Respiratory Syncytial Virus (RSV) Pneumonia in Children

Prevention of RSV. Two agents have been approved for protecting high-risk infants against RSV pneumonia:

  • Palivizumab (Synagis) is known as a monoclonal antibody, a genetically engineered antibody, which targets the RSV virus. It is given by an injection into the muscle.
  • RSV immune globulin (RespiGam) is made up of antibodies to RSV that are obtained from the blood of healthy infants. RespiGam is given as a shot.

Treatment of RSV. Ribavirin is the first treatment approved for respiratory syncytial virus pneumonia, although it has only modest benefits. The American Academy of Pediatrics recommends it for children at high risk for serious complications of RSV. In one study, a combination of ribavirin with RSV immune globulin was more effective than either drug alone.

Drugs called bronchodilators, which open up the airways, are sometimes used to treat RSV infection. However, evidence is conflicting. One study involving albuterol, a common bronchodilator, found that epinephrine may be more effective.