Penicillins second generation

Information about Penicillins second generation

The penicillinase-resistant [also referred to as second generation penicillins] are semisyntheic modifications of natural penicillins that are resistant to bacterial enzyme beta-lactamase, which accounts for typical penicillin resistance.

Mechanism of action of Penicillins second generation

The natural penicillins from which the second generation penicillins are made are bactericidal antibiotics naturally derived from the mold, Penicillium chrysogenum. Their basic structure includes a thiazolidine ring connected to a beta-lactam ring with a variable side chain. As a class, the penicillins bind to bacterial proteins and inhibit synthesis of the bacterial cell wall, causing cell lysis particularly in rapidly growing organisms. Bacterial resistance to penicillin is usually mediated by beta-lactamase, an enzyme which destroys the beta-lactam ring of penicillin, rendering it inactive. The penicillinase-resistant penicillins resist the hydrolysis of the beta-lactam ring by the bacterial enzymes. They are active against most organisms that are susceptible to the natural penicillins (although less active than penicillin G) and have extended coverage against resistant forms.

Mechanism of action of Penicillins second generation

Three major penicillinase-resistant penicillins are available in the United States: dicloxacillin (dye klox" a sil' in), oxacillin (ox" a sil' in) and nafcillin (naf sil' in).

• Dicloxacillin is orally available; oxacillin and nafcillin have both oral and parenteral formulations, the latter being given by the intramuscular or intravenous route. Other formulations available abroad or in the past include methicillin, cloxacillin and flucloxacillin, which have been associated with a higher frequency of side effects including hepatic injury.

The major indications for dicloxacillin, oxacillin and nafcillin are moderate-to-serious infections with susceptible penicillinase-producing staphylococci; these agents are also active against organisms susceptible to natural penicillins, but are less active than the natural penicillins.

Penicillin antibiotics

• penicillins first generation (natural penicillins)
  • benzathine penicillin, procaine penicillin, penicillin g, penicillin v, penicillin vk

• penicillins second generation (penicillinase-resistant penicillins)
  • cloxacillin, dicloxacillin, flucloxacillin, methicillin, nafcillin, oxacillin

• penicillins third generation (aminopenicillins)
  • amoxicillin, ampicillin, ampicillin-sulbactam, bacampicillin, pivampicillin
• see also amoxicillin-clavulanate

• penicillins fourth generation (extended-spectrum penicillins)
  • carbenicillin, mezlocillin, piperacillin, piperacillin-tazobactam, ticarcillin, ticarcillin-clavulanate

• Dailymed label info on Penicillins second generation
• FDA Penicillins second generation

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