At the time of their launch, many newly-introduced antibiotics demonstrate excellent efficacy to treat bacterial infections, including serious diseases. However, each time a patient takes an antibiotic, the drug may kill most of the bacteria, but a few of them could survive and later multiply, creating drug-resistant strains. Recently, drug resistance has been becoming a major issue, particularly in certain infections such as tuberculosis and hospital-based staphylococcus infections. About 160 antibiotics are currently available, and pharmaceutical companies introduce new ones from time to time, but the new agents usually belong to an existing antibiotic category and share similar mechanisms of action, thus increasing the chances of the development of drug resistance. The overprescribing of antibiotics and improper drug usage may be contributory factors to the development of resistance.
In this context, linezolid is a particularly interesting antibacterial because it is the first member of a new class of antibiotics known as oxazolidinones. This is the first new antibacterial drug class that we are seeing in decades. Linezolid is indicated for the treatment of nosocomial infections involving Gram-positive organisms including methicillin-resistant Staph aureus (MRSA), vancomycin-resistant enterococcus faecium and multi-resistant strains of Strep pneumoniae. Since gram-positive bacteria are often considered to be among the greatest challenges in hospital infections, linezolid will be especially useful because it can be employed to tackle drug resistant cases where other antibiotics prove to be ineffective. For years, vancomycin has been employed as a last line of defense against virulent staphylococci, and vancomycin resistance is a dreaded situation. Linezolid can play a vital role here. Clinical studies involving more than 4,000 primarily hospital-treated patients have shown that linezolid is effective in treating infections caused by Gram-positive bacteria, including resistant infections. Linezolid also has some activity against other organisms such as Legionella species, Chlamydia pneumoniae, and Haemophilus influenzae.
The drug is given orally or parenterally. Thus it is possible to continue oral treatment following initial parenteral therapy, with the benefits of dosing flexibility and convenience, and the option of completing therapy as an out patient. Linezolid is generally well tolerated. In clinical trials, adverse events for patients receiving linezolid and comparator drugs were similar. Linezolid’s adverse effects include diarrhoea, headache, nausea and vomiting. These are usually mild to moderate in intensity and limited in duration.
Linezolid is advocated for use in complicated skin infections and nosocomial pneumonia caused by methicillin-resistant Staphylococcus aureus (MRSA); concurrent bacteremia associated with vancomycin-resistant Enterococcus faecium; and concurrent bacteremia associated with community-acquired pneumonia caused by penicillin-susceptible Streptococcus pneumoniae. The linezolid brand Zyvox is expected to be an important product for its manufacturer Pharmacia Upjohn. In view of its efficacy in resistant infections, the drug has earned the tag of a “superantibiotic”. Doctors believe that linezolid should be reserved for resistant infections, but the manufacturers suggest that it could be a first line of therapy. Zyvox sales are expected to cross $500 million, but at least one analyst believes that if the drug is used in the way the company wants, annual sales could surpass $1 billion.