Antibiotics

Linezolid

Linezolid is the first licensed member of a new class of antibiotics, the oxazolidinones, that bind to a specific site on the bacterial ribosome and inhibit microbial protein synthesis. This mechanism of action provides an antimicrobial activity that is independent of the resistance status toward other antibiotics. Some studies suggest that linezolid may be associated with improved survival and clinical cure rates compared with vancomycin in patients with nosocomial pneumonia. Linezolid is a suitable alternative to vancomycin in nosocomial infections by MRSA, particularly in pneumonia. Linezolid does not require adjustment for renal function at a dosage of 600 mg every 12 hours. A close monitoring of the blood cell count should be done in case of preexisting myelosuppression and during prolonged treatment. Resistance of MRSA to linezolid is for the moment of limited concern; although an expensive drug, it has a documented cost-effectiveness in comparison to vancomycin

Daptomycin

Daptomycin is a cyclic lipopeptide that is active only against gram-positive organisms, and has been approved for the treatment of complicated skin and soft-tissue infections with activity against resistant and susceptible isolates of S aureus. Its once-daily parenteral dosing (4 mg/kg intravenously) and safety profile (except for some concerns of rhabdomyolysis) make daptomycin an attractive option for the treatment of staphylococcal infections. Unfortunately, daptomycin may not be a useful agent for deep-seated tissue infections. The current use of daptomycin should be limited to skin infections and possibly bacteremia and/or endocarditis.

Quinupristin-Dalfopristin

Quinupristin-dalfopristin is a semisynthetic parenteral streptogramin with activity against most of the gram-positive pathogens. Data suggest that quinupristin-dalfopristin is probably not a better option than vancomycin, with both agents seemingly having limited activity against MRSA pneumonia in this study. Although antimicrobial resistance has not been an overriding concern, the side-effect profile of quinupristin-dalfopristin (myalgia, arthralgia, and thrombophlebitis) and its lack of proven efficacy over vancomycin have limited its overall use.

Tigecycline

Tigecycline is the first glycylcycline to be launched and is one of the very few antimicrobials with activity against both gram-negative bacteria and MRSA. In contrast to classic tetracyclines, tigecycline can only be administered parenterally, and its major side effect appears to be dose-related nausea and emesis. The dosing regimen for tigecycline is a 100-mg loading dose followed by 50 mg twice daily in patients with complicated skin and skin structure infections and intra-abdominal infections. Tigecycline may prove particularly useful for the treatment of surgical wound infections, in which both gram-negative bacteria and MRSA are likely pathogens. Tigecycline may also have a role in the treatment of infections due to MDR pathogens.

Selected Investigational Agents

Ceftobiprole. Ceftobiprole is a novel broad-spectrum cephalosporin with potent bactericidal activities against MRSA and penicillin-resistant S pneumoniae. Ceftobiprole is being investigated in patients with pneumonia and complicated skin infections.

Dalbavancin. Dalbavancin is a lipoglycopeptide antimicrobial that has been studied in phase 2 trials for complicated skin and skin structure infections and catheter-related bloodstream infection. Dalbavancin is a bactericidal agent whose long terminal plasma half-life (9-12 days) allows for the unique dosing of 1000 mg given on day 1 and 500 mg given on day 8. The long half-life may turn out to be the strength of dalbavancin allowing for more convenient treatment options in patients requiring prolonged antibiotic therapy (eg, infective endocarditis or osteomyelitis).

Telavancin. Telavancin is another lipoglycopeptide in phase 2 development. Telavancin exerts bactericidal activity against gram-positive bacteria, including MRSA. In a recent double-blind, randomized, controlled trial, telavancin proved effective for the treatment of complicated skin and skin structure infections given once daily. Telavancin's once-daily dosing is appealing. Additional studies are ongoing to determine the efficacy of this agent in other infections, including pneumonia.

Excerpts from the article: The Role of Antibiotics in the Management of Serious Hospital-Acquired Infections

The Role of Antibiotics in the Management of Serious Hospital-Acquired Infections

For more information on tigecycline, please see: NursingCenter - Professional Development - CE Article

Telithromycin (Ketek) is the first ketolide antibiotic, a class of drugs that is chemically similar to the macrolides. Although slightly different in molecular structure, telithromycin has properties and uses similar to the macrolide antibiotics azithromycin, clarithromycin, erythromycin, and dirithromycin.

Telithromycin is indicated to treat:

• acute bacterial sinusitis caused by Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis , or Staphylococcus aureus
• acute bacterial exacerbation of chronic bronchitis caused by Streptococcus pneumoniae, H. influenzae , or Moraxella catarrhalis
• mild to moderate community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae (including multidrug resistant strains), H. influenzae, Moraxella catarrhalis, Chlamydia pneumoniae , or Mycoplasma pneumoniae.

This drug is the first of the macrolide-like antibiotics to be shown effective for treating CAP caused by isolates of Streptococcus pneumoniae that are resistant to two or more of the following antibiotics: penicillin, second-generation cephalosporins, macrolides, tetracyclines, and trimethoprim/sulfamethoxazole.

Telithromycin may cause hepatic dysfunction, including increased liver enzymes and hepatitis, with or without jaundice. These changes usually reverse when therapy is discontinued.

Adverse reactions: diarrhea, headache, nausea , vomiting, antibiotic-associated colitis, dizziness, visual disturbances

Supplied as: 400-mg film-coated tablets
Dosage: 800 mg daily for 5 days for acute bacterial sinusitis and acute bacterial exacerbations of chronic bronchitis; 800 mg daily for 7 to 10 days for CAP

Nursing considerations: (1) Advise the patient to avoid driving and other potentially hazardous activities if telithromycin causes visual disturbances such as blurred vision, difficulty focusing, and diplopia. (2) Dosage adjustment isn't necessary for a patient with hepatic impairment. (3) The appropriate dosage for a patient with severe renal impairment (creatinine clearance less than 30 ml/minute) hasn't been established.

Excerpts from the article: NursingCenter - Library - Journal Issue - Article

Warning about telithromycin (Ketek) - Liver Problems

June, 2006 - The FDA has issued a public health advisory regarding the antibiotic telithromycin (Ketek). A study reported in the January 20 issue of the Annals of Internal Medicine describes three cases of serious to fatal liver failure in patients taking telithromycin. Of the three patients, one died, one required a liver transplant, and one recovered. Premarketing studies had shown infrequent and usually reversible liver damage, much like other approved antibiotics. Causal relationships haven’t been established, but the FDA wanted to release the advisory while they continue to investigate the problem. They advise that patients taking telithromycin should be monitored for liver problems and that the drug be stopped if signs and symptoms of liver problems develop. Patients should be advised to report yellowing of the eyes or skin and blurry vision to their health care provider. Prescribers are cautioned to only use the drug for susceptible infections.

NDHnow.com - Drug Updates - telithromycin
http://www.fda.gov/medwatch/safety/2...s/Ketek_PI.pdf

Here is another wonderful resource on antibiotics:

Antibiotics Affecting the Bacterial Cell Wall

http://connection.lww.com/Products/a...er-CH38rev.pdf

Penicillins

Sulfonamides

Free article from RNweb:

Drug Watch 2006: Antibiotics

After reading this article you should be able to:

1. Differentiate between the different classes of antimicrobials.
2. Compare and contrast the four new antimicrobials.
3. Develop a teaching plan for a patient taking the new antimicrobials.

http://rnweb.com/rnweb/article/artic....jsp?id=368380