Most respiratory tract infections are caused by viruses. Bacterial respiratory tract infections are usually treated empirically with antibiotic therapy that targets the most probable causative pathogens. Recommended antibiotic regimens for outpatient treatment of some common respiratory tract infections are listed in Table 1 for adults and Table 2 for children.

In a clinical trial conducted by the CDC's Tuberculosis Trials Consortium in collaboration with the NIH-funded AIDS Clinical Trials Group, a new 4-month regimen for treatment of drug-susceptible pulmonary tuberculosis was found to be noninferior to 6 months of standard treatment.

On June 25, 2021, the FDA added a warning to the Fact Sheets for the mRNA-based COVID-19 vaccines manufactured by Pfizer/BioNTech (Comirnaty) and Moderna (Spikevax) about an increased risk of myocarditis and pericarditis following administration of the vaccines.

Treatment of community-acquired pneumonia (CAP) is usually empiric, with selected antibiotic regimens directed against some of the most common causative pathogens. Recommended empiric regimens are listed in Table 2; recommended antibiotic dosages for treatment of CAP are listed in Tables 3 and 4. Joint guidelines for treatment of CAP by the American Thoracic Society and the Infectious Diseases Society of America (ATS/IDSA) were updated in 2019.

This issue includes reviews of drugs for glaucoma, age-related macular degeneration (AMD), bacterial conjunctivitis, and dry eye disease. Allergic conjunctivitis is reviewed in a separate issue.

Lefamulin (Xenleta – Nabriva), a semisynthetic pleuromutilin antibiotic, has been approved by the FDA for IV and oral treatment of community-acquired bacterial pneumonia (CABP) in adults. It is the first systemic pleuromutilin antibiotic to be approved in the US; retapamulin (Altabax), a 1% topical ointment for treatment of impetigo, was approved in 2007.

The FDA has approved omadacycline (Nuzyra – Paratek), a semisynthetic tetracycline derivative, for once-daily IV and oral treatment of community-acquired bacterial pneumonia (CAP) and acute bacterial skin and skin structure infections (ABSSSIs) in adults.

The FDA has approved delafloxacin (Baxdela – Melinta), an anionic fluoroquinolone antibiotic, for oral and parenteral treatment of adults with acute bacterial skin and skin structure infections (ABSSSIs), including those caused by methicillin-resistant Staphylococcus aureus (MRSA). It is the first fluoroquinolone to be approved for treatment of MRSA.

View the Comparison Table: Some Systemic Fluoroquinolones (online only)

Bacterial infections in adults are generally treated empirically, with the antibiotic covering most, but not all, of the potential causative pathogens. For some infections, culture and sensitivity testing can guide treatment, allowing for use of narrower-spectrum antibiotics. The recommended dosages and durations of antibiotic treatment for common respiratory, skin, and urinary tract infections are listed in Tables 1-3. Infectious disease experts now recommend shorter treatment durations for many infections to reduce the development of antimicrobial resistance and minimize adverse effects.

The text and tables that follow include recommendations for management of sexually transmitted infections (STIs) other than HIV and viral hepatitis. Some of the indications and dosages recommended here have not been approved by the FDA.

The FDA has announced that it is requiring changes in the labeling of systemic fluoroquinolones to warn that the risk of serious adverse effects, including tendinitis, peripheral neuropathy and CNS effects, generally outweighs their benefit for the treatment of acute sinusitis, acute exacerbations of chronic bronchitis, and uncomplicated urinary tract infections. For these infections, the new labels will recommend reserving fluoroquinolones for patients with no other treatment options.

Antimicrobial prophylaxis can decrease the incidence of postoperative surgical site infection after some procedures. Since the last Medical Letter article on this subject, consensus guidelines have been published. Recommendations for prophylaxis in specific surgical procedures are listed in Table 1.

The FDA has approved ceftolozane/tazobactam (Zerbaxa – Cubist), a combination of a new cephalosporin antibiotic and a beta-lactamase inhibitor, for intravenous treatment of complicated urinary tract and intra-abdominal infections in adults.

The FDA is requiring new warnings about peripheral neuropathy in the labeling of all oral and injectable fluoroquinolones. The potential for this class of antibiotics to cause peripheral neuropathy was first identified more than 10 years ago and a warning was added to their labels in 2004. The new warnings are based on a recent review of the FDA’s Adverse Event Reporting System (AERS) database.1

The onset of peripheral neuropathy can occur rapidly, often within a few days of starting a fluoroquinolone, and in some patients the disorder may be permanent. Symptoms include pain, tingling, burning, numbness, weakness, and change in sensation to touch, pain, and temperature in the arms and/or legs. If peripheral neuropathy develops in a patient taking a fluoroquinolone, the drug should be stopped and an antibacterial from a different class should be used instead.2

1. FDA Drug Safety Communication: FDA requires label changes to warn of risk for possibly permanent nerve damage from antibacterial fluoroquinolone drugs taken by mouth or by injection. Available at http://www.fda.gov. Accessed November 1, 2013.

2. Drugs for bacterial infections. Treat Guidel Med Lett 2013; 11:65.

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Many infections can be transmitted during sexual contact. The text and tables that follow include recommendations for management of sexually transmitted infections (STIs) other than HIV, viral hepatitis, and enteric infections. Some of the indications and dosages recommended here have not been approved by the FDA.

The text that follows reviews some common bacterial infections and their empiric treatment pending the results of culture and susceptibility testing. The recommendations made here are based on the results of susceptibility studies, clinical trials, and the opinions of Medical Letter reviewers. Tables 1 and 2 list the usual dosages of antibacterial drugs.

Drugs for glaucoma, age-related macular degeneration, bacterial conjunctivitis, and dry eyes are reviewed here. Drugs for the treatment of allergic conjunctivitis will be reviewed in a future issue of Treatment Guidelines on Drugs for Allergic Disorders.

Antimicrobial prophylaxis can decrease the incidence of postoperative infection, particularly surgical site infection, after some procedures. Recommendations for such prophylaxis are listed in the table that begins on page 74. Antimicrobial prophylaxis for dental procedures to prevent endocarditis was recently discussed in The Medical Letter.

Tuberculosis (TB) is still a common cause of death worldwide, and the prevalence of drug-resistant TB poses challenges to its treatment and control. Guidelines with detailed management recommendations are available from the American Thoracic Society, Centers for Disease Control and Prevention (CDC) and Infectious Diseases Society of America (IDSA).

The FDA has required the manufacturer of the secondgeneration antipsychotic quetiapine (Seroquel) to add a warning to the labeling saying that use of the drug should be avoided in combination with other drugs that prolong the electrocardiographic QTc interval (Table 1). The warning is based only on postmarketing reports of QT-interval prolongation in patients who overdosed on the drug, had concomitant illness, or were taking other drugs known to cause electrolyte imbalances or increase the QT interval. QT prolongation can lead to torsades de pointes, a potentially fatal cardiac arrhythmia.

A Medical Letter reader has asked us to review the safety of the fluoroquinolone antibiotic levofloxacin (Levaquin – Ortho-McNeil-Janssen), which has just been approved for generic use by the FDA and has been at the center of some recent lawsuits regarding the adequacy of its safety warnings.

The FDA has approved ceftaroline fosamil (Teflaro – Forest), an intravenous (IV) cephalosporin, for treatment of acute bacterial skin and skin structure infections, including those caused by methicillin-resistant Staphylococcus aureus (MRSA), and for treatment of community-acquired bacterial pneumonia in adults. It is the first beta-lactam antibiotic approved for treatment of MRSA.

The text below reviews some common bacterial infections and their treatment. The recommendations made here are based on the results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants.

Drugs for glaucoma, age-related macular degeneration, bacterial conjunctivitis, and dry eyes are reviewed here. Ophthalmic drugs can have local and systemic adverse effects. In addition, for some elderly patients, the complexity of self-administering numerous ophthalmic drugs may be the limiting factor in their ability to care for themselves. Drugs for the treatment of allergic conjunctivitis will be reviewed in a future issue of Treatment Guidelines on Drugs for Allergic Disorders.

The FDA has approved the fluoroquinolone besifloxacin 0.6% ophthalmic suspension (Besivance - Bausch & Lomb) for treatment of bacterial conjunctivitis caused by susceptible bacteria. According to the manufacturer, this product was developed specifically for ophthalmic use in a specialized vehicle designed to prolong contact time on the ocular surface. Besifloxacin is not available for systemic use.

Even though the incidence continues to decline in the United States, tuberculosis (TB) is still a common cause of death worldwide, and the prevalence of drug-resistant TB poses severe challenges to its treatment and control. Guidelines with detailed management recommendations are available from the Centers for Disease Control and Prevention (CDC), American Thoracic Society and Infectious Diseases Society of America (IDSA).

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain procedures. Recommendations for prevention of surgical site infection are listed in the table that begins on page 48. Antimicrobial prophylaxis for dental procedures to prevent endocarditis is discussed in The Medical Letter 2007; 49:99.

The FDA has added a boxed warning to fluoroquinolone package inserts about tendon injuries that may occur as a result of their use. Tendinitis or tendon rupture may occur rarely with systemic use of any fluoroquinolone, either while the drug is being taken or for up to several months afterwards.

Fluoroquinolone-related tendon injury is rare; estimates for its incidence in the general population range from 0.14% to 0.4%. The risk is higher for patients >60 years old and for those taking corticosteroids. For patients with organ transplants, the incidence may be as high as 15%.1 A case-control study in Italy involving 22,194 cases of non-traumatic tendinitis and 104,906 controls found that fluoroquinolone use was significantly associated with tendon disorders in general (OR 1.7; 95% CI 1.4-2.0), tendon rupture (OR 1.3; 95% CI 1.0-1.8), and Achilles tendon rupture (OR 4.1; 95% CI 1.8-9.6). Achilles tendon rupture occurred with fluoroquinolone treatment in one of every 5989 patients in general and in one of every 1638 patients >60 years old.2

Widespread use of fluoroquinolones, particularly for treatment of respiratory infections, has produced substantial bacterial resistance to this class of drugs and has been associated with an increase in the incidence and severity of Clostridium difficile disease.3 Even when bacterial pneumonia is considered a likely possibility, other drugs are generally preferred, at least in non-elderly, otherwise healthy patients.4

1. F Muzi et al. Fluoroquinolones-induced tendinitis and tendon rupture in kidney transplant recipients: 2 cases and a review of the literature.Transplant Proc 2007; 39:1673.
2. G Corrao et al. Evidence of tendinitis provoked by fluoroquinolone treatment: a case-control study. Drug Saf 2006; 29:889.
3. Treatment of Clostridium difficile-associated disease (CDAD). Med Lett Drugs Ther 2006; 48:89.
4. Drugs for community-acquired bacterial pneumonia. Med Lett Drugs Ther 2007; 49:62.

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Doripenem (Doribax - Ortho-McNeil Janssen), an intravenous (IV) carbapenem antibiotic with a spectrum of activity similar to that of imipenem and meropenem, has been approved by the FDA for treatment of complicated intra-abdominal and urinary tract infections. Use of doripenem for treatment of nosocomial pneumonia, including ventilator-associated pneumonia, is still under FDA review.

Information about empirical treatment of bacterial infections, emerging trends in antimicrobial resistance, new drugs and new data about older drugs continue to become available. Usual pathogens and empiric treatment for some common types of infections are summarized in the text and a table listing the drugs of choice and alternatives for each pathogen begins on page 40. The recommendations made here are based on the results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants.

Even though the incidence continues to decline, tuberculosis (TB) is still a problem in the United States. Treatment of TB can be divided into treatment of latent infection and treatment of active disease. Atable listing the first-line drugs used for treatment of TB with their doses and adverse effects can be found on page 16. Other guidelines with more detailed management recommendations are available.

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain procedures. Recommendations for prevention of surgical site infection are listed in this article.

Methicillin-resistant Staphylococcus aureus (MRSA) infections, which have been a concern for many years, previously occurred primarily in hospitalized patients and those recently treated with antibiotics. In the past few years, there has been an increasing incidence worldwide of community-associated (CA) MRSA infections in patients without recent antibiotic exposure or contact with the healthcare system.

Tuberculosis (TB) is still a problem in the United States, even though the incidence continues to decline in most of the country (MMWR Morbid Mortal Wkly Rep 2004; 53:209). Treatment of TB can be divided into treatment of latent infection diagnosed by a positive PPD and treatment of active clinical TB. Guidelines with detailed management recommendations are available from the US Centers for Disease Control and Prevention (CDC) (MMWR Morbid Mortal Wkly Rep 2003; 52RR-11:1).

Gemifloxacin (Factive - Oscient), a new oral fluoroquinolone antibiotic, has been approved by the FDA for 5 days' treatment of acute bacterial exacerbations of chronic bronchitis (ABECB) and 7 days' treatment of mild to moderate community-acquired pneumonia (CAP) in adults. For the next 6-8 months it will only be available, presumably for commercial reasons, in states east of the Rocky Mountains.

Telithromycin (Ketek - Aventis) has been approved by the FDA for oral treatment of mild to moderate community-acquired pneumonia, acute exacerbations of chronic bronchitis and acute bacterial sinusitis in patients age 18 and older. The drug is the first in a new class of antibiotics, the ketolides, derived from the macrolide erythromycin. Telithromycin has been marketed in Europe since 2001.

Antimicrobial prophylaxis can decrease the incidence of infection, particularly surgical site infection, after certain operations, but this benefit must be weighed against the risks of toxic and allergic reactions, emergence of resistant bacteria, adverse drug interactions, superinfection and cost. Medical Letter consultants generally recommend antimicrobial prophylaxis only for procedures with high infection rates, those involving implantation of prosthetic material, and those in which the consequences of infection are likely to be especially serious.

Two new fluoroquinolone solutions, moxifloxacin 0.5% (Vigamox - Alcon) and gatifloxacin 0.3% (Zymar - Allergan) are now available in the US for ophthalmic use in treatment of bacterial conjunctivitis.

New drugs for bacterial infections and new information about older drugs continue to become available. Empirical treatment of some common bacterial infections is discussed in this article. A table listing the drugs of choice and alternatives for each pathogen begins on page 18. These recommendations are based on results of susceptibility studies, clinical trials and the opinions of Medical Letter consultants. Local resistance patterns should be taken into account. Trade names are listed on page 24.

The choice of drugs for treatment of pneumonia depends on the most likely pathogens causing the infection and local antimicrobial resistance patterns. Factors such as severity of illness, presence of co-morbid conditions and whether the infection is community or hospital-acquired also need to be considered.

The July 2003 edition of the Canadian Adverse Reaction Newsletter, published by Health Canada (the Canadian FDA), reported that the Health Canada database had received more spontaneous reports of hypoglycemia (19) and hyperglycemia (7) with gatifloxacin (Tequin) than with other quinolone antibiotics.

Augmentin XR (GlaxoSmithKline), an oral extended-release combination of amoxicillin and the beta-lactamase inhibitor clavulanic acid, is now being promoted for treatment of acute bacterial sinusitis and community-acquired pneumonia. Augmentin XR contains a higher dose of amoxicillin than Augmentin.

Gatifloxacin and moxifloxacin are now available for once-daily treatment of patients with community-acquired pneumonia, acute bacterial exacerbations of chronic bronchitis, or acute sinusitis.