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 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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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.

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.

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.

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.

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.

Superseded--purchase updated Parasitic Infections article
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.

Note: Drugs for Parasitic Infections, revised and updated, is now available to both subscribers and nonsubscribers on our web site. This article, a bi-annual feature of The Medical Letter for many years, will not be published as a printed issue in 2002, but is included in the 16th edition of The Medical Letter Handbook of Antimicrobial Therapy. The handbook is now available and can be ordered by calling customer service at 1-800-211-2769.

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.

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

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.

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.

(Superseded by the 2013 version. Click here to purchase.)
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 lists first-choice and alternative drugs for most parasitic infections.

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.

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.

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.

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.

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).