Since 2007, antimicrobial prophylaxis for dental procedures has been recommended to prevent viridans group streptococcal infective endocarditis only for patients at highest risk of an adverse outcome. Limiting use to such patients does not appear to have led to an increased incidence of infective endocarditis or increased mortality due to infective endocarditis.

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.

The FDA has approved vonoprazan, a potassium-competitive acid blocker, copackaged with amoxicillin (Voquezna Dual Pak – Phathom) and with amoxicillin and clarithromycin (Voquezna Triple Pak) for treatment of Helicobacter pylori infection in adults. Vonoprazan is the first potassium-competitive acid blocker to be approved in the US. It has been available in Japan for treatment of various acid-related disorders since 2014. Vonoprazan is not available alone in the US.

The FDA has approved vonoprazan, a potassium-competitive acid blocker, copackaged with amoxicillin (Voquezna Dual Pak – Phathom) and with amoxicillin and clarithromycin (Voquezna Triple Pak) for treatment of Helicobacter pylori infection in adults. Vonoprazan is the first potassium-competitive acid blocker to be approved in the US. It has been available in Japan for treatment of various acid-related disorders since 2014. Vonoprazan is not available alone in the US.

Gastroesophageal reflux disease (GERD) is the most common GI condition encountered in the outpatient setting; it affects about 20% of people in the US.

View the Comparison Table: H2-Receptor Antagonists and PPIs

More antibiotics are prescribed for treatment of acute otitis media (AOM) than for any other infection in young children. Children with AOM typically present with otalgia, fever, and bulging and erythema of the tympanic membrane.

Lyme disease in the US is caused by the spirochete Borrelia burgdorferi, which is transmitted to humans by Ixodes scapularis (blacklegged [deer] tick) and I. pacificus (western blacklegged tick). Most cases of Lyme disease occur in late spring and early summer in northeastern and mid-Atlantic states, the upper Midwest, and in northern California. B. mayonii, which is also transmitted by I. scapularis, has been shown to cause a similar illness in the upper Midwest.

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.

The FDA has approved a fixed-dose combination of omeprazole, amoxicillin, and rifabutin (Talicia – RedHill) for treatment of Helicobacter pylori infection in adults. Talicia is the first rifabutin-based product to be approved for this indication.

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 warned that use of the macrolide antibiotic clarithromycin (Biaxin, and generics) may increase the risk of cardiovascular morbidity and mortality in patients with heart disease.

Gastroesophageal reflux disease (GERD) is the most frequent GI condition encountered in the outpatient setting; it affects about 20% of the US population. Heartburn and regurgitation are the classic symptoms of GERD.

View the Comparison Table: Drugs for GERD and Peptic Ulcer Disease

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.

About 50% of the world’s population is infected with Helicobacter pylori. These gastric bacteria can cause chronic inflammation and have been associated with development of gastritis, peptic ulcer disease, gastric adenocarcinoma, and gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Eradication of H. pylori can promote gastric healing, prevent recurrence of duodenal and gastric ulcers, and reduce the incidence of gastric cancer. Guidelines for treatment of H. pylori infection were updated recently.

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.

Most cases of Lyme disease in the US occur between May and September in the Northeastern, Mid-Atlantic, and North Central states.

H2-RECEPTOR ANTAGONISTS (H2RAs) — Currently available H2RAs are listed in Table 1. These drugs inhibit the action of histamine at the H2-receptor of the gastric parietal cell, decreasing basal acid secretion and, to a lesser degree, food-stimulated acid secretion. All H2RAs are about equally effective for treatment of PUD and GERD. H2RAs are faster acting than PPIs in relieving symptoms of dyspepsia or GERD, but they are not as effective as PPIs in relieving symptoms or in healing erosive esophagitis. Repeated administration of H2RAs leads to pharmacologic tolerance and has been associated with the development of new dyspeptic symptoms. Rebound acid hypersecretion can occur after stopping H2RAs.

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.

A reader who took the online continuing medical education (CME) exam for issue 1406 (Med Lett Drugs Ther 2012; 54:101) pointed out that the first question assumed that a rash following oral administration of ampicillin would be due to allergy. Perhaps we should have mentioned in our article on penicillin allergy that late-appearing maculopapular rashes associated with oral ampicillin or amoxicillin are generally considered non-allergic and need not preclude subsequent administration of ampicillin or amoxicillin.

Only a small minority of patients who say they are allergic to penicillin will have a reaction if they take a penicillin.

Peptic ulcer disease (PUD) is usually caused by nonsteroidal anti-inflammatory drugs (NSAIDs) or by infection with Helicobacter pylori. Gastroesophageal reflux disease (GERD) can be caused by transient lower esophageal sphincter relaxation, reduced lower esophageal sphincter tone, hiatal hernia, delayed gastric emptying or hormonal changes due to pregnancy. Acid suppressive therapy is the cornerstone of management for both PUD and GERD.

Most cases of Lyme disease in the US occur between May and September in the Northeastern, Mid-Atlantic and North Central states.

Many infections can be transmitted during sexual contact. The text and tables that follow are limited to management of sexually transmitted infections (STIs) other than HIV, viral hepatitis and enteric infections. The drugs of choice, their dosages and alternatives are listed in a table that begins on page 54. A table listing the adverse effects of some of these antimicrobials begins on page 58.

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.

Readers have asked us to update our 2004 article on tablet splitting. Breaking drug tablets in half is a common practice, but the FDA recently advised consumers against it (FDA Consumer Health Information, July 2009).

The FDA has approved an extended-release formulation of amoxicillin (Moxatag – MiddleBrook) for once-daily treatment of pharyngitis or tonsillitis caused by Streptococcus pyogenes in adults and children ≥12 years old. Approval was based on an unpublished study that found once-daily treatment with Moxatag 775 mg for 10 days non-inferior to penicillin V 250 mg four times a day for 10 days in eradication of S. pyogenes.

For decades, the drug of choice for oral treatment of streptococcal pharyngitis in adolescents and adults has been penicillin V 250 mg taken three or four times a day.1 Amoxicillin is equally effective, but penicillin is generally recommended because of its narrower spectrum. In adults, immediate-release amoxicillin is usually dosed 375-500 mg two to three times a day, but giving it in a higher dose (750-1000 mg) once a day appears to be equally effective for treatment of strep throat.2-4

Each Moxatag tablet contains 775 mg of amoxicillin divided into one immediate-release and two delayedrelease components. Compared to a similar dose of immediate-release amoxicillin suspension, absorption of amoxicillin from the new formulation is slower, resulting in a lower peak serum concentration, but the elimination half-life and amoxicillin exposure (AUC) are similar. S. pyogenes is susceptible to these serum concentrations, but they may be too low to treat other types of infections.

A 10-day supply of Moxatag is expected to cost about $100 compared to $4 for a similar course of penicillin V or immediate-release amoxicillin.5 There is no good reason to prescribe Moxatag.

1. A Bisno et al. Practice guidelines for the diagnosis and management of group A streptococcal pharyngitis. Infectious Disease Society of America. Clin Infect Dis 2002; 35:113.
2. P Shvartzman et al. Treatment of streptococcal pharyngitis with amoxycillin once a day. BMJ 1993; 306:1170.
3. HM Feder Jr. et al. Once-daily therapy for streptococcal pharyngitis with amoxicillin. Pediatrics 1999; 103:47.
4. HW Clegg et al. Treatment of streptococcal pharyngitis with once-daily compared with twice-daily amoxicillin: a noninferiority trial. Pediatr Infect Dis J 2006; 25:761.
5. Retail cost at one Walgreens pharmacy. February 27, 2009.

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Peptic ulcers caused by treatment with nonsteroidal anti-inflammatory drugs (NSAIDs) are mainly gastric ulcers. Most duodenal and other gastric ulcers are caused by the gram-negative bacillus Helicobacter pylori. Gastroesophageal reflux disease (GERD) is caused by gastric acid reflux into the esophagus. Drugs that suppress gastric acid production are the primary treatment for GERD and peptic ulcers.

Retapamulin (re-tap'-a-mue'-lin; Altabax - Glaxo SmithKline) is a topical antibiotic recently approved by the FDA for treatment of bullous and non-bullous impetigo due to Streptococcus pyogenes and methicillin-susceptible Staphylococcus aureus. It is available as a 1% ointment by prescription only.

On page 100 of the article "Major Changes in Endocarditis Prophylaxis for Dental, GI and GU Procedures", under the section Highest-Risk Procedures, the word "rubber" should have been omitted. Placement of orthodontic rubber bands is not a highest-risk procedure that justifies prophylaxis; placement of orthodontic (metal) bands is. An orthodontic band is a metal ring that surrounds the tooth and is pressed into place causing movement in closely-spaced teeth and sometimes bleeding when the bands are placed close to the gumline.

The American Heart Association has issued its revised guidelines for prevention of infective endocarditis. Antimicrobial prophylaxis for dental procedures is now recommended only for patients at the highest risk of severe consequences from endocarditis who are undergoing the highest-risk procedures. Endocarditis prophylaxis is no longer recommended for gastrointestinal (GI) and genitourinary (GU) procedures. When these changes are implemented, the number of patients receiving antimicrobial prophylaxis to prevent endocarditis should decline sharply.

Many infections can be transmitted during sexual contact. The text and tables that follow are limited to management of sexually transmitted infections (STIs) other than HIV, viral hepatitis and enteric infections. Guidelines are available from the US Centers for Disease Control and Prevention (CDC) with detailed recommendations for treatment of these diseases.

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.

Many physicians believe that antimicrobial prophylaxis before procedures that may cause transient bacteremia can prevent endocarditis and prosthetic joint infection in patients at increased risk for these disorders. The effectiveness of this common practice has never been established by controlled trials in humans.

The pathogenesis of acne is multifactorial: follicular hyperkeratinization, Propionibacterium acnes bacteria, sebum production, androgens and inflammation have all been implicated. P. acnes, a gram-positive microaerophilic bacterium, plays an important role in the development of acne lesions by secreting chemotactic factors that attract leukocytes to the follicle, causing inflammation.

Lyme disease in North America is caused by the spirochete Borrelia burgdorferi, which is transmitted to humans by Ixodes scapularis or pacificus ticks. These ticks may also carry other pathogens; coinfection with Babesia microti or Anaplasma phagocytophilum (formerly Ehrlichia) has been reported.1 In 2001 and 2002, 12 states (CT, DE, ME, MD, MA, MI, NH, NJ, NY, PA, RI, WI) reported about 95% of all the Lyme disease in the US, but cases occurred in all states except HI, MT and OK. Most Lyme disease in North America occurs between May and September.

Breaking drug tablets in half is a common practice. In some cases, a lower drug dose may be as effective as a higher one, with fewer adverse effects. Sometimes tablets are split to achieve an intermediate dose between marketed strengths. When 2 tablet sizes cost the same, as they often do, splitting the larger size saves money. Is this a reasonable practice?

Many infections can be transmitted during sexual contact. The text and tables that follow are limited to management of sexually transmitted infections (STIs) other than HIV, viral hepatitis and enteric infections. Guidelines are available from the US Centers for Disease Control and Prevention (CDC) with detailed recommendations for treatment of these diseases (MMWR Recomm Rep 2002; 51, RR-6:1). New guidelines are expected soon.

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.

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.

Most peptic ulcers not caused by nonsteroidal anti-inflammatory drugs (NSAIDs) are associated with infection of the gastric mucosa by the gram-negative bacilli Helicobacter pylori. The majority of NSAID-related ulcers are gastric. H. pylori infection causes both duodenal and gastric ulcers. Eradication of H. pylori promotes healing and markedly decreases recurrence of both duodenal and gastric ulcers (A Shiotamni and DY Graham, Med Clin North Am 2002; 86:1447; FKL Chan and WK Leung, Lancet 2002; 360:933). The first step in the management of peptic ulcers is the diagnosis and treatment of H. pylori.

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.

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.

Superseded by Handbook of Antimicrobial Therapy
The Medical Letter article on Drugs and Vaccines against Biological Weapons, published in the previous issue (October 15, 2001, page 87), included a brief discussion of post-exposure prophylaxis of inhalation anthrax. Recent events call for more detail.

Concerns have arisen anew about possible use of biological weapons. The pathogens considered most likely to be used for this purpose are discussed in this article. A good source for additional information is www.usamriid.army.mil/education/bluebook.html.

Lyme disease is caused by the spirochete Borrelia burgdorferi and transmitted to humans by Ixodes ticks. These ticks may also carry other pathogens; co-transmission of Babesia and Ehrlichia species has been reported.

Many infections can be transmitted during sexual contact. The text and tables [in this article] are limited to treatment of non-HIV infections associated primarily with sexual transmission.

Cefdinir (Omnicef - Parke-Davis), a third-generation oral cephalosporin, has been approved by the FDA for treatment of acute sinusitis, otitis media, acute exacerbations of chronic bronchitis, pharyngitis, community-acquired pneumonia and skin infections. Other drugs available for these indications are reviewed in The Medical Letter Handbook of Antimicrobial Therapy, 1998.

Now that US Secretary of Defense has decided to vaccinate more than 2 million memebers of the US armed forces against anthrax, US physicians may be asked to answer some questions about the vaccine and the disease.

Fosfomycin, a broad-spectrum antibiotic used parenterally in Europe for many years, has been approved by the US Food and Drug Administration (FDA) as fosfomycin tromethamine (Monurol - Forest) for single-dose oral treatment of uncomplicated urinary tract infections in women.

Lyme disease, a multisystem infection transmitted by ixodid ticks and caused by the spirochete Borrelia burgdorferi is the most common vector-borne illness in the USA. Cases have been reported in 44 states, and also in Canada and many countries in Europe and Asia (ME Falagas and SL Gorbach, Infect Dis Clin Pract, 5:217, 1996).

Most peptic ulcers not caused by nonsteroidal anti-inflammatory drugs (NSAIDs) are now thought to be associated with infection of the gastric mucosa by the gram-negative bacilli Helicobacter pylori. The majority of NSAID-related ulcers are gastric. H. pylori have been associated with both duodenal and gastric ulcers. Eradication of H. pylori promotes healing and markedly decreases recurrence of both duodenal and gastric ulcers (AH Soll, JAMA, 275:622, 1996).

The US Food and Drug Administration (FDA) recently approved the marketing of clarithromycin (Biaxin - Abbott), a macrolide antibiotic, and omeprazole (Prilosec - Astra Merck), a proton pump inhibitor, for concurrent use in treatment of duodenal ulcers associated with Helicobacter pylori.

Ceftibuten (Cedax - Schering), an oral cephalosporin similar to cefixime (Suprax - Medical Letter, 31:73, 1989), has been approved by the US Food and Drug Administration (FDA) for treatment of acute otitis media, pharyngitis or tonsillitis, and for acute bacterial exacerbations of chronic bronchitis.

Results of recently completed clinical trials have led to some changes in recommendation for treatment of human immunodeficiency virus (HIV) and other infections associated with AIDS.

Most peptic ulcers not caused by nonsteroidal anti-inflammatory drugs (NSAIDs) are now thought to be associated with infection of the gastric mucosa by the gram-negative bacilli Helicobacter pylori (NIH Consensus Development Panel, JAMA, 272:65, July 6, 1994). NSAID-related ulcers are usually gastric. H. pylori have been associated with both duodenal and gastric ulcers.

Piperacillin/tazobactam (Zosyn - Lederle), an antibiotic combination product, has been approved by the US Food and Drug Administration for intravenous treatment of intra-abdominal, pelvic, skin, and skin-structure infections and for community-acquired pneumonia of moderate severity.

Results of recently completed clinical trials have led to some changes in recommendations for treatment of human immunodeficiency virus (HIV) and other infections associted with AIDS.

Cefpodoxime proxetil (Vantin - Upjohn), a new third-generation oral cephalosporin, has been approved for marketing by the US Food and Drug Administration. It is available for twice-daily treatment of pharyngitis, upper and lower respiratory infections, otitis media, urinary tract infections, skin and soft tissue infections, and for single-dose treatment of uncomplicated gonorrhea in men or women and anorectal gonorrhea in women.

Enoxacin (en ox' a sin; Penetrex - Rh ne-Poulenc Rorer), a fluoroquinolone antimicrobial for oral use, has now been marketed in the USA for treatment of urinary tract infections and uncomplicated urethral or cervical gonorrhea.

Lyme disease, a multisystem infection transmitted by ixodid ticks and caused by the spirochete Borrelia burgdorferi the most common vector-borne illness in the USA. It occurs, mainly in the northeast, upper midwest, and California, but cases have been reported in 48 states, and also in Canada and many countries in Europe.

Clarithromycin (Biaxin - Abbott) and azithromycin (Zithromax - Pfizer), two macrolide antibiotics chemically related to erythromycin, have been approved by the US Food and Drug Administration for treatment of respiratory, skin, and skin structure infections. Azithromycin has also been approved for treatment of nongonococcal urethritis and cervicitis caused by Chlamydia trachomatis.

Drugs that accelerate healing and prevent relapse or reurrence of peptic ulcers act either by decreasing gastric acidity or by enhancing mucosal defense mechanisms. Risk factors that may cause breakdown of mucosal defenses include the use of aspirinor other nonsteroidal anti-inflammatory drugs (NSAIDs) and the presence of Helicobacter pylori bacterial in the gastric antrum (AH Soll, Engl J Med, 322:909, 1990; WL Peterson, N Engl J Med, 324:1043, 1991).

A growing number of clinical trials now permits some consensus on the treatment of human immunodeficiency virus (HIV) and other infections associated with acquired immune deficiency syndrome (AIDS) in adults.

Many physicians believe that antimicrobial prophylaxis before procedures that may cause transient bacteremia can prevent endocarditis in patients with valvular heart disease, prosthetic heart valves or other structural cardiac abnormalities. The recommendations in the table are based on the opinions of Medical Letter consultants.

Cefixime (Suprax - Lederle), an oral cephalosporin antibiotic, was recently approved for marketing by the US Food and Drug Administration. Claimed to be the first oral third-generation cephalosporin, the new drug is offered for once-a-day treatment of otitis media, pharyngitis, bronchitis and urinary tract infections.

Lyme disease, a multisystem bacterial transmitted by Ixodid ticks, particularly in early summer, continues to be a common problem in the USA and many other countries. Since last year (Medical Letter, 30:65, 1988), some new information has become available, but data on the choice, dosage and duration of antibiotic therapy are still available, but data on the choice, dosage and duration of antibiotic therapy are still limited.

A penicillin is the drug of choice for treatment of many infections, but allergic reactions to these drugs occur frequently and, rarely, can be fatal. From 5% to 20% of patients have a history of a rash or some other reaction while taking a penicillin, but maculopapular rashes with ampicillin or amoxicillin, especially in children with infectious mononucleosis, are probably not allergic.

Lyme Disease, a multisystem inflammatory disorder transmitted by lxodid ticks and caused by the spirochete Borrelia burgdorferi, is now the most common tick-transmitted illness in the USA. It has been reported in 32 states and on all other continents except Antarctica. Infected ticks have been found not only in wooded areas, but also on well-maintained suburban lawns (RC Falco and D Fish, Am J Epidemiol, 127:826, April 1988). Optimal treatment for this newly discovered disease is still being determined, but some recommendations based on published experience and work in progress can be made.

Cefuroxime axetil (Ceftin - Glaxo), an oral form of the second-generation parenteral cephalosporin cefuroxime (Zinacef), was recently marketed in the USA. Previously available oral cephalosporins are the first-generation drugs cephalexin (Keflex; and others), cephradine (Anspor; and others) and cefadroxil (Duricef; and others), and the second-generation cefaclor (Ceclor); second-generation cephalosporins have more activity against gram-negative bacteria.