Category: Health News
Created: 9/25/2008 2:00:00 AM
Last Editorial Review: 9/25/2008
The penicillins were the first antibiotics discovered as natural products from the mold Penicillium. They have a common chemical structure which they share with the cephalopsorins, and are classed as the beta-lactam antibiotics. Penicillins are generally bacteriocidal-that is, they kill bacteria rather than inhibiting growth.
Penicillinase-Resistant Penicillins
Penicillinase-resistant penicillins were developed because of the increasing resistance of staphylococci to natural penicillins. They include methicillin, oxacillin, cloxacillin, dicloxacillin, nafcillin. The penicillinase-resistant penicillins have a more narrow spectrum of activity than the natural penicillins. Their antimicrobial activity is aimed directly against penicillinase-producing strains of gram-positive cocci, particularly Staphylococcal species. These antibacterial agents are sometimes called anti-staphylococcal penicillins.
Classification of Penicillins
Beta-lactam antibiotics are characterized by three fundamental structural requirements: the fused beta-lactam structure, a free carboxyl acid, and one or more substituted amino acid side chains.
Methicillin has been discontinued in the US because of the occurrence of interstitial nephritis.
The penicillins can be further subdivided. From narrow to broad range of effectiveness they include:
Aminopenicillins
The aminopenicillins (ampicillin, amoxicillin, bacampicillin) were the first penicillins discovered to be active against gram-negative bacteria (such as E. coli and H. influenzae). Aminopenicillins are acid-resistant and may be taken with food. Amoxicillin is better absorbed from the gastrointestinal tract than other penicillins and provides higher and more sustained blood antibiotic levels. Amoxicillin and ampicillin are used primarily to treat mild infections such as otitis media, sinusitis, bronchitis, urinary tract infections and bacterial diarrhea. Amoxicillin is the agent of choice for the treatment of otitis media.
Extended Spectrum Penicillins
Extended Spectrum Penicillins (sometimes called anti-pseudomonal penicillins) include both alpha-carboxypenicillins (carbenicillin and ticarcillin) and acylaminopenicillins (piperacillin, azlocillin, and mezlocillin). These antibiotics have similar spectrums of activity as the aminopenicillins but with additional activity against several gram negative organisms of the family Enterobacteriaceae. Like the aminopenicillins, these agents are susceptible to inactivation by beta-lactamases. These antibiotics may be used alone or in combination with Aminoglycosides.
Natural Penicillins
Natural penicillins include Penicillin G, Procaine, Penicillin G, Penicillin V, Benzathine. These antibiotics were the first agents in the penicillin family to be introduced for clinical use. The natural penicillins are based on the original penicillin-G structure. They are effective against gram-positive strains of streptococci, staphylococci, and some gram-negative bacteria such as meningococcus. Penicillin V is the chemically improved form of penicillin, that combines acid stability with immediate solubility and rapid absorption. It is highly active against staphylococci streptococci, and pneumococci.
Yury Bayarski is the contributing author of HealthyStock.net.
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