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.

A reader has questioned why the label for the COX-2 selective NSAID celecoxib (Celebrex, and generics), which contains a sulfonamide moiety, states that it is contraindicated for use in patients with an allergy to sulfonamides, while the labels of some other sulfonamide drugs recommend either caution or no precautions at all. The concept of cross-reactivity among sulfonamide drugs, particularly between antibacterial and nonantibacterial sulfonamides, has been controversial for many years.

View the Comparison Table: Some Antibiotics for MRSA Skin and Skin Structure Infections

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 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.

Aminosalicylates are effective for induction and maintenance of remission in mild to moderate ulcerative colitis. They are not recommended for treatment of Crohn's disease.

FORMULATIONS — Oral mesalamine is rapidly absorbed in the small intestine and most of the drug does not reach the colon. Pentasa releases mesalamine gradually throughout the gastrointestinal tract. Delzicol, Asacol HD, Lialda, and Apriso delay the release of the drug until it reaches the distal ileum and colon. Sulfasalazine (Azulfidine, and generics), balsalazide (Colazal, and others), and olsalazine (Dipentum) are prodrugs; mesalamine is azo-bonded to a second moiety and released in the colon following bacterial cleavage of the bond. Mesalamine is also available as an enema (Rowasa, and generics) and as a rectal suppository (Canasa).

The treatment of atrial fibrillation includes anticoagulation, rate control, and rhythm control. New US guidelines for the management of atrial fibrillation have recently been published.

Methicillin-resistant Staphylococcus aureus (MRSA), which was traditionally a nosocomially-acquired organism but now frequently occurs in the absence of healthcare exposure, is the predominant cause of suppurative skin and soft-tissue infections in many parts of the US. Community-associated MRSA usually causes furunculosis, purulent cellulitis, and abscesses, but necrotizing fasciitis, necrotizing pneumonia, and sepsis can also occur.

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.

The pathogenesis of acne is multifactorial: follicular hyperkeratinization, bacteria, sebum production, androgens, and inflammation all play a role. The gram-positive microaerophilic bacteria Propionibacterium acnes promote development of acne lesions by secreting chemotactic factors that attract leukocytes to the follicle, causing inflammation.

A reader suggested that our July 23 article on Drugs for Urinary Tract Infection (Med Lett Drugs Ther 2012; 54:57)¹ should have included information on the cost of the drugs we recommended for treatment of acute uncomplicated cystitis.

Trimethoprim/sulfamethoxazole DS — Generic formulations are available at large discount pharmacies for $4 for 20 tablets. Trimethoprim/sulfamethoxazole DS is generally found on tier 1 (lowest co-pay) of insurance company formularies.

Nitrofurantoin monohydrate/macrocrystals — The wholesale acquisition cost of the generic formulation is about $2.50 per tablet (PricePointRx™).² The drug is on tier 1 of some insurance company formularies, but on tier 2 or 3 of others.

Fosfomycin — Available only as Monurol, a single dose of fosfomycin is effective in most cases of acute uncomplicated cystitis, but the manufacturer charges a wholesale acquisition cost of more than $40 for that dose (PricePointRx™).² Most insurance companies place Monurol on tier 3 of their formularies, or do not include it on their formularies at all.

Not recommended: Ciprofloxacin – Fluoroquinolones should not be used empirically to treat acute uncomplicated cystitis. The fact that ciprofloxacin is available at large discount pharmacies for $4 for 20 500-mg tablets and is on tier 1 on most insurance company formularies may be part of the reason for its continued overuse.

1. Drugs for urinary tract infection. Med Lett Drugs Ther 2012; 54:57.

2. PricePointRx™. Reprinted with permission by FDB. All rights reserved. ©2012. http://www.firstdatabank.com/support/drug-pricing-policy.aspx. Accessed July 31, 2012. Actual retail prices may be higher.

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The most recent guidelines from the Infectious Diseases Society of America (IDSA) and its European counterpart on the choice of antimicrobials for treatment of uncomplicated urinary tract infections (UTIs) in non-pregnant women focus on the unnecessary use of fluoroquinolones to treat uropathogens that are increasingly becoming resistant to them. Resistance of Escherichia coli to ciprofloxacin in the US has increased from 3% in 2000 to 17.1% in 2010.

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.

Inflammatory bowel disease (IBD) is either Crohn's disease or ulcerative colitis. Drug selection is guided by disease type (Crohn's versus ulcerative colitis), severity and location and whether the goal is induction or maintenance of remission. Table 1 on page 66 lists the drugs used to treat IBD with their formulations and cost. Table 2 on page 68 lists the drugs of choice and their doses for different indications. Table 3 on page 71 lists the drugs' adverse effects and recommendations for monitoring. More detailed guidelines are available from the American College of Gastroenterology.

The recent Medical Letter article on vancomycin dosing and monitoring briefly mentioned use of an alternative antibiotic for treatment of methicillin-resistant Staphylococcus aureus (MRSA) with reduced susceptibility to vancomycin. Some readers have asked for more information on this subject.

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Disease-modifying anti-rheumatic drugs (DMARDs) are now used early in the treatment of rheumatoid arthritis (RA) to prevent irreversible damage to joints and minimize toxicities associated with nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment could also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

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A reader expressed disappointment that our recent listing of “Some Warfarin Drug Interactions”1 did not include acetaminophen. Perhaps it should have. Acetaminophen can increase the anticoagulant effect of warfarin, particularly with continued use, but it does so inconsistently. The mechanism of this interaction has not been established, but may be related to an acetaminophen metabolite inhibiting vitamin K-epoxide reductase, the target for warfarin’s anticoagulant effect.2

Patient susceptibility varies, possibly on a genetic basis; occasional use of acetaminophen generally has little or no effect on the international normalized ratio (INR) in patients on chronic warfarin therapy, but in some, even a few grams of the drug may cause a dramatic increase in INR. One study in healthy subjects found no effect of acetaminophen 4 g per day for 2 weeks, while another study in patients with the same acetaminophen dose for the same period of time found a moderate increase in INR.3,4 It might be prudent to monitor INR in patients on chronic warfarin therapy more closely than usual when they take more than 2 g per day of acetaminophen for more than a few days.

1. Pharmacogenetic-based dosing of warfarin. Med Lett Drugs Ther 2008; 50:39.
2. HH Thijssen et al. Paracetamol (acetaminophen) warfarin interaction: NAPQI, the toxic metabolite of paracetamol, is an inhibitor of enzymes in the vitamin K cycle. Thromb Haemost 2004; 92:797.
3. D Kwan et al. The effects of acetaminophen on pharmacokinetics and pharmacodynamics of warfarin. J Clin Pharmacol 1999; 39:68.
4. I Mahe et al. Paracetamol: A haemorrhagic risk factor in patients on warfarin. Br J Clin Pharmacol 2005; 59:371.

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Warfarin sodium (Coumadin, and others) and other coumarin anticoagulants prevent thrombosis, but patient response is highly variable and overanticoagulation can lead to hemorrhage. Genotyping patients for single nucleotide polymorphisms (SNPs) that affect coumarin metabolism and sensitivity may help clinicians estimate the therapeutic warfarin dose. The FDA has added a note to warfarin labeling recommending lowrange doses for patients with such genetic variations. Commercial tests for these variants are now available and cost about $500 per test.

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.

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.

To prevent irreversible damage to joints and minimize toxicities associated with nonsteroidal anti-inflammatory drugs (NSAIDs) and corticosteroids, disease modifying anti-rheumatic drugs (DMARDs) are now used early in the treatment of rheumatoid arthritis (RA). The DMARDs listed in the table on page 84 have no immediate analgesic effects, but can control symptoms and have been shown to delay and possibly stop progression of the disease. The NSAIDs listed in the table on page 88 have analgesic and anti-inflammatory effects, but may not affect the disease process. Oral corticosteroids can rapidly relieve joint symptoms and control systemic manifestations, but their chronic use is associated with many complications.

Head lice occur in all age groups, but especially in elementary school children during the winter months. Infestations are becoming more difficult to treat because of increasing resistance to the chemical pediculicides commonly used, particularly those that are available over-the-counter (OTC).

Parasitic infections are found throughout the world. With increasing travel, immigration, use of immunosuppressive drugs and the spread of AIDS, physicians anywhere may see infections caused by previously unfamiliar parasites. The table below lists first-choice and alternative drugs for most parasitic infections. The brand names and manufacturers of the drugs are listed in this article.

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.

Many different drugs are now used to treat rheumatoid arthritis. Nonsteroidal anti-inflammatory drugs (NSAIDs), listed in the table on page 26, have analgesic and anti-inflammatory effects, but may not affect the disease process. Corticosteroids can provide rapid relief of joint symptoms and control of systemic manifestations, but chronic use is associated with many complications. The "disease-modifying" anti-rheumatic drugs (DMARDs), listed on page 29, have no immediate analgesic effects, but can control symptoms and may delay progression of the disease (American College of Rheumatology Subcommittee on Rheumatoid Arthritis Guidelines, Arthritis Rheum 2002; 46:328). Interactions of anti-rheumatic drugs with other drugs are listed in The Medical Letter Handbook of Adverse Drug Interactions, 2003.

Many drugs can cause psychiatric symptoms, but a causal connection is often difficult to establish. Psychiatric symptoms that emerge during drug treatment may also be due to the underlying illness, previously unrecognized psychopathology, or psychosocial factors. The withdrawal of some drugs can cause symptoms such as anxiety, psychosis, delirium, agitation or depression.

Patients planning to travel to other countries often ask physicians for advice about immunizations and prevention of diarrhea and malaria. More detailed advice for travelers is available from the CDC at 877-FYI-TRIP (877-394-8747) or www.cdc.gov/travel.

Older patients are especially susceptible to drug-induced cognitive impairment. They are more likely to be taking multiple drugs, to have higher blood levels of those drugs because of renal or hepatic dysfunction, and to have pre-existing cognitive problems that make it difficult to detect the role of drugs causing new symptoms or making old ones worse.

Two types of oral contraceptives are available in the USA: combination oral contraceptives that contain both an estrogen and a progestin, and progestin-only contraceptives, or "mini-pills."Used as directed, all oral contraceptives marketed in the USA are similarly effective in preventing pregnancy.

Dofetilide (Tikosyn - Pfizer), a new methanesulfonamide antiarrhythmic drug, has recently been marketed for oral treatment of atrial fibrillation and flutter.

Patients planning to travel to other countries often ask pysicians for advice about immunizations and prevention of diarrhea and malaria. Legal requirements for entry and epidemiological conditions in different countries vary from time to time, often unpredictably, but some reasonable recommendations can be made.

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.

Penciclovir 1% cream (Denavir - SmithKline Beecham) has been approved by the US Food and Drug Administration (FDA) for treatment of recurrent orolabial herpes simplex virus (HSV) infections in adults. Acyclovir (Zovirax) is also available in a topical formulation for treatment of herpes simplex infections, but is approved by the FDA only for use in immunocompromised patients. Oral drugs approved for treatment of some herpes simplex infections, but not recurrent orolabial infections, include acyclovir, valacyclovir (Valtrex) and famciclovir (Famvir), which is rapidly hydrolyzed to penciclovir in vivo (Medical Letter, 36:97, 1994).

Men with primary or secondary hypogonadism require lifelong androgen replacement to prevent osteoporosis and maintain normal muscle mass, erythropoiesis and sexual function (AM Matsumoto, Endocrinol Metab Clin North Am, 23:857, 1994). Until recently, the standard treatment for male hypogonadism has been an intramuscular injection of a long-acting testosterone ester every two to three weeks, which leads to serum testosterone concentrations that are high for a few days, normal for a few days more, and then may be subnormal until the next dose. Two transdermal preparations of testosterone are now marketed in the USA. Testoderm (Alza) must be worn on the scrotum. Androderm (SmithKline Beecham), a newer patch, can be applied to the upper arms, thighs, back or abdomen. All androgens are controlled substances in the USA.

Patients planning to travel to other countries often ask physicians for advice about immunizations and prevention of diarrhea and malaria. More detailed advice for travelers is available from the CDC at 877-FYI-TRIP (877-394-8747) or www.cdc.gov/travel.

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.

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.

Atovaquone (Mepron - Burroughs Wellcome), a hydroxynaphthoquinone, was recently approved by the US Food and Drug Administration (FDA) for oral treatment of mild to moderate Pneumocystis carinii pneumonia (PCP) in patients who cannot tolerate trimethoprim-sulfamethoxazole (Septra, Bactrim, and others). PCP is a common opportunistic infection and frequent cause of death in patients 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.

Loracarbef (Lorabid - Lilly), a new beta-lactam antibiotic with antimicrobial activity similar to the second-generation cephalosporins, has been approved by the US Food and Drug Administration for treatment of respiratory, skin, and urinary tract infection caused by susceptible organisms in both adults and children. It will probably compete with drugs such as trimethoprim-sulfamethoxazole (Bactrim, Septra, and others), amoxicillin-clavulanic acid (Augmentin), cefaclor (Ceclor), cefuroxime axetil (Ceftin), and cefprozil (Cefzil - Medical Letter, 34:63, 1992).

Cefprozil (Cefzil - Bristol-Myers Squibb), a new oral second-generation cephalosporin, was recently released in the USA for treatment of pharyngitis, bronchitis, otitis media, and skin and skin-structure infections.

Temafloxacin (Omniflox - Abbott) and lomefloxacin (Maxaquin - Searle) are the latest fluoroquinolone antimicrobial agents to be approved by the US Food and Drug Administration (FDA) for oral treatment of various infections. Previously marketed include norfloxacin (Noroxin - Medical Letter, 29:25, 1987), ciprofloxacin (Cipro - Medical Letter, 30:11, 1988), and ofloxacin (Floxin - Medical Letter, 33:71, 1991). Norfloxacin is marketed only for treatment of urinary tract infections, and lomefloxacin only for treatment of urinary tract infections and bronchitis known to be caused by Haemophilus influenzae or Moraxella catarrhalis. Ciprofloxacin and ofloxacin are also available in parenteral formulations.

Patients planning to travel to other countries often ask physicians for advice about immunizations and prevention of diarrhea and malaria. Legal requirements for entry and epidemiological conditions in different countries vary from time to time, often unpredictably, but some reasonable recommendations can be made. More detailed information is available in Health Information for International Travel, published annually by the Centers for Disease Control (CDC), which can be obtained from the Superintendent of Documents, US Government Printing Office, Washington, DC 20402. Up-to-date automated information is available by telephone from the CDC (404-332-4559).

Almost 300,000 cases of epidemic cholera have occurred in the Western Hemisphere in 1991, mostly in South and Central America (Morbid Mortal Weekly Rep, 40:562, Aug 16, 1991). The few US cases caused by the epidemic strain have been in returning travelers or associated with contaminated food they brought back illicitly, with no secondary spread to date.

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.

Ciprofloxacin, previously available orally (Cipro - Medical Letter, 30:11, 1988) and for ophthalmic use (Ciloxan - Medical Letter, 33:52, May 31, 1991), is now the first fluoroquinolone antibiotic to become available in the USA in an intravenous (IV) formulation. Cipro I.V. (Miles) is being promoted as an alternative to third-generation cephalosporins, aminoglycosides, and other drugs used for treatment of serious infections.

Ofloxacin (Floxin - McNeil, Ortho), a new fluoroquinolone antibacterial agent, was recently marketed in the USA for oral treatment of various infections caused by susceptible microorganisms. Ofloxacin is the third fluoroquinolone to become available in this country. Norfloxacin (Noroxin - Medical Letter, 29:25, 1987) is marketed only for treatment of urinary tract infections. Ciprofloxacin (Cipro - Medical Letter, 30:11, 1988), like ofloxacin, is approved for use in a variety of infections.

Since the last Medical Letter review of cephalosporin antibiotics (volume 25, page 57, 1983), many new cephalosporins have become available in the USA.

Pneumocystis carinii pneumonia (PCP) occurs in nearly 80% of patients with the acquired immune deficiency syndrome (AIDS) and is a common cause of morbidity and mortality. Oral trimethoprim-sulfamethoxazole (Bactrim; and others), intravenous isethionate (Pentam 300) and other systemic drugs have been used to prevent PCP, but in AIDS patients, all of these agents can occasionally cause severe adverse effects (Medical Letter, 30:94, 1988). Recently, the US Food and Drug Administration approved marketing of aerosolized pentamidine isethionate (NebuPent - LyphoMed) for this indication. Another pentamidine aerosol (Pneumopent - Fisons) is available in Canada through the Emergency Drug Release Program.

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.

Trimetrexate glucuronate (Parke-Davis), an investigational drug, is now available in the USA from the National Institute of Allergy and Infectious Diseases (NIAID) for treatment of selected AIDS patients with Pneumocystis carinii pneumonia (PCP). For this indication, trimetrexate is always used concurrently with leucovorin (Wellcovorin; and others).

Pneumocystis carinii pneumonia (PCP) is a common cause of death in patients with acquired immune deficiency syndrome (AIDS). PCP is the first serious opportunistic infection in more than 60% of patients with AIDS, and about 80% of AIDS patients develop PCP at least once (AE Glatt et al, N Engl J Med, 318:1439, June 2, 1988). Many studies using drugs to prevent PCP in patients with AIDS have recently been reported.

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.

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.

Ciprofloxacin hydrochloride (Cipro - Miles), a synthetic antibacterial agent, was recently marketed in the USA for oral treatment of a wide variety of infections. Ciprofloxacin is the second fluoroquinolone to become available in this country; norfloxacin (Noroxin - Medical Letter, 29:25, 1987) is marketed only for treatment of urinary tract infections. Fluoroquinolones are more potent and have a much broader spectrum of activity than older quinolones such as nalidixic acid (NegGram).