Zyvox

Zyvox is an antibiotic used to treat various types of bacterial infections, such as pneumonia, skin infections, and infections that are resistant to other antibiotics.

Zyvox is marketed by Pfizer.

Other Names

• Linezolid

Uses

A scanning electron micrograph (SEM) of Gram-positive Enterococcus sp. bacteria, which are notoriously linked as etiologic agents responsible for nosocomial, or "hospital-borne" illnesses, such as "Vancomycin Resistant Enterococci", or VRE infections. Source: CDC/Janice Carr

Zyvox is an antibiotic used in the treatment of the following infections caused by susceptible strains of the following microorganisms:

• Enterococcus faecium infections resistant to vancomycin. These are called Vancomycin resistant enterococci or VRE. Enterococcus bacteria are "commensal" in nature, which means that they normally colonize the human digestive tract, and become pathogenic when their host becomes immunosuppressed, such as after a surgical procedure, or during a prolonged illness, or in immunocompromised individuals who might be undergoing chemotherapy, or in the case of AIDS patients. VRE poses little or nor problem for healthy people with strong immune systems, where normal bacterial flora in their digestive tract helps keep VRE from getting out of control. VRE is dangerous because it cannot be controlled with antibiotics, and it causes life-threatening infections in people with compromised immune systems - HIV/AIDS, the very young, the very old, and the very ill.

• Pneumonia caused by Staphylococcus aureus or Streptococcus pneumoniae

• Skin infections caused by Staphylococcus aureus, Streptococcus pyogenes, or Streptococcus agalactiae

How Zyvox is Taken

Zyvox is available in 400 mg and 600 mg tablets. It is also available in an orange-flavored 100 mg/5 mL oral suspension and a 2 mg/mL injection.

How Zyvox Works

Zyvox's active ingedient is linezolid. Linezolid belongs to a new family of synthetic antibiotics called oxazolidinones. Since this class of antibiotics are synthetic, not natural products of plants or fungi, it is hoped resistance to them will develop more slowly.

Linezolid (and other oxazolidinones) inhibit bacterial protein synthesis through a mechanism of action different from that of other antibiotics. As a fortunate result, cross-resistance between linezolid and other classes of antibiotics is unlikely. Linezolid binds to a site on the 23S ribosomal RNA of the 50S subunit of the bacterial ribosome. This binding prevents the bacteria from synthesizing protein necessary for the function of cells: since human cells make proteins differently from bacterial cells, these antibiotics don't affect protein synthesis in human cells.

How the Body Affects Zyvox

Zyvoxis rapidly and extensively absorbed after oral dosing. Circulating levels peak at 1 to 2 hours after dosing.

Linezolid is primarily metabolized by oxidation; however, preliminary studies show that this metabolism does not appear to involve the liver as is the case with many other drugs.

Approximately 90% of the dose is excreted through the urine, while the remainder is excreted through the feces.

Side Effects

Rare but more serious side effects include:

• hives; difficulty breathing; swelling of the face, lips, tongue, or throat
• pale skin, easy bruising or bleeding, unusual weakness
• fever, chills, body aches, flu symptoms
• diarrhea that is watery or bloody
• blurred vision, trouble seeing colors
• numbness, burning, pain, or tingling in the hands or feet
• seizures
• muscle pain or weakness, numb or cold feeling in the arms and legs, trouble breathing, nausea with vomiting, and fast or uneven heart rate

Less serious side effects may be more likely to occur, such as:

• headache, dizziness
• nausea, vomiting, constipation, stomach pain or upset
• insomnia
• itching
• discolored tongue, unusual or unpleasant taste in the mouth
• vaginal itching or discharge
• yeast infection in the mouth

Risks and Precautions

Eating foods containing tyramine while taking Zyvox can raise blood pressures to dangerous levels. Foods that have high levels of tyramine include:

• aged cheeses or meats
• pickled or fermented meats
• smoked or air-dried meats
• sauerkraut
• soy sauce
• alcoholic and nonalcoholic beer
• red wine

Zyvox may cause lactic acidosis (the build up of lactic acid in the body). Lactic acidosis can start slowly and gradually get worse. Symptoms include unusual muscle pain and weakness, trouble breathing, fast or uneven heart rate, nausea, vomiting, stomach pain, and numbness or cold feeling in your arms or legs.

Early signs of lactic acidosis generally get worse over time and this condition can be fatal.

Serotonin syndrome (marked by cognitive dysfunction, abnormally high fever, and incoordination) has been reported with the co-administration of Zyvox and selective serotonin reuptake inhibitors (SSRIs).

Peripheral and optic neuropathy have been reported in patients treated with Zyvox, primarily those patients treated for longer than the maximum recommended duration of 28 days. Visual blurring has been reported in some patients treated with Zyvox for less than 28 days.

Convulsions have been reported in patients when treated with Zyvox.

Drug Interactions

Zyvox use may have interactions with the following drugs:

• cyclosporine (Neoral, Sandimmune, Gengraf)
• sirolimus (Rapamune),tacrolimus (Prograf)
• basiliximab (Simulect), efalizumab (Raptiva), muromonab-CD3 (Orthoclone)
• mycophenolate mofetil (CellCept)
• azathioprine (Imuran), leflunomide (Arava), etanercept (Enbrel)
• cold or allergy medicines containing pseudoephedrine or phenylephrine
• drugs that weaken your immune system (such as chemotherapy or steroids)
• SSRI antidepressants such as citalopram (Celexa), escitalopram (Lexapro), fluoxetine (Prozac, Sarafem), fluvoxamine (Luvox), paroxetine (Paxil), or sertraline (Zoloft)
• MAO inhibitors such as isocarboxazid (Marplan), phenelzine (Nardil), rasagiline (Azilect), selegiline (Eldepryl, Emsam), or tranylcypromine (Parnate)
• medicines to treat Parkinson's disease, such as amantadine (Symmetrel), carbidopa or levodopa (Lodosyn, Parcopa, Sinemet), entacapone (Comtan), levodopa (Larodopa), pergolide (Permax), pramipexole (Mirapex), ropinorole (Requip), or tolcapone (Tasmar)

Effectiveness

The effectiveness of Zyvox has been studied in vancomycin-resistant enterococcal infections (VRE), nosocomial pneumonia, pneumonia caused by multi-drug resistant S. pneumoniae (MDRSP), and complicated skin infections.

Vancomycin-resistant enterococcal infections

A study with 145 adult patients with vancomycin-resistant enterococcal infections compared high-dose treatment with Zyvox (600 mg) against low-dose treatment with Zyvox (200 mg) given every 12 hours either intravenously (IV) or orally for 7 to 28 days.

The overall cure rate was higher in the high-dose patients (67%) than in the low-dose patients (52%), although the difference was not statistically significant.^[1]

Nosocomial pneumonia

A study of 396 adult patients with nosocomial pneumonia (pneumonia contracted by a patient while under medical care) was conducted.

203 patients received Zyvox IV 600 mg every 12 hours, and 193 patients received vancomycin IV 1 g every 12 hours for a duration of 7 to 21 days.

The cure rates in clinically evaluable patients were 57% for Zyvox-treated patients and 60% for vancomycin-treated patients.^[2]

Pneumonia caused by multi-drug resistant S. pneumoniae (MDRSP)

Zyvox was studied for the treatment of community-acquired and hospital-acquired pneumonia due to MDRSP by pooling clinical data from seven previous studies. The pooled population consisted of all patients with S. pneumoniae isolated at baseline.

The pooled cure rates for patients with community-acquired pneumonia due to MDRSP were 73%. The pooled clinical cure rates for patients with hospital-acquired pneumonia due to MDRSP were 67%.^[3]

Complicated skin infections

Adult patients with complicated skin infections were enrolled in a trial comparing study medications administered IV followed by medications given orally for a total of 10 to 21 days of treatment. 400 patients received Zyvox IV 600 mg every 12 hours followed by Zyvox tablets 600 mg every 12 hours; the other 419 patients received oxacillin IV 2 g every 6 hours followed by dicloxacillin 500 mg every 6 hours orally.

The cure rates in clinically evaluable patients were 90% in Zyvox-treated patients and 85% in oxacillin-treated patients.^[4]

Alternatives

Appropriate alternatives to Zyvox will heavily depend upon the details of the clinical scenario in question such as the patient's age, the site and severity of the infection and the particular bacterial strain involved. Some alternative antibiotics that may be considered in lieu of or in combination with Zyvox include:

• vancomycin
• moxifloxacin
• rifampin
• clindamycin
• trimethoprim-sulfamethoxazole

References

1. ↑ Linezolid in the treatment of vancomycin-resistant enterococcus: a dose comparative, multicenter phase III trial. Intersci Conf Antimicrob Agents Chemother. 2000 Sep 17-20; 40: 488. Abstract
2. ↑ Linezolid (PNU-100766) versus vancomycin in the treatment of hospitalized patients with nosocomial pneumonia: a randomized, double-blind, multicenter study. Clin Infect Dis. 2001 32:3, 402-412. Full Text | PDF
3. ↑ A prediction rule to identify low-risk patients with community-acquired pneumonia. New Engl J Med. 1997;336 (4):243-250. Full Text
4. ↑ Randomized comparison of linezolid (PNU-100766) versus oxacillin-dicloxacillin for treatment of complicated skin and soft tissue infections. Antimicrob Agents and Chemo. 2000 Dec; 44(12):3408-3413. Abstract | Full Text | PDF

External Links

Pfizer: Zyvox

FDA: Linezolid

Rx List: Zyvox (Linezolid)[[Category:|Category:]]