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Penicillins

Up Carbapenems Cephalosporins ESBL Penicillins


Spectrum of activity

Class

Example

Antimicrobial spectrum

Natural penicillins

Benzylpenicillin

Gm +ves, anaerobes and selected Gm -ves

Penicillinase resistant penicillins

Flucloxacillin, cloxacillin

Penicillin-resistant staphylococci. Also active against streptococci

Aminopenicillins

Amoxycillin, ampicillin

As for penicillin G plus Gram –ve cocci, and Enterobacteriaceae. The addition of b lactamase inhibitors expands the Gram +ve, -ve and anaerobic spectrum

Carboxypenicillins

Carbenicillin, ticarcillin

As for aminopenicillins plus Gm –ve rods resistant to ampicillin, including P. aeruginosa.

Ureidopenicillins

Piperacillin, azlocillin

Similar to carboxypenicillins. Addition of ß lactamase inhibitor (as in piperacillin/tazobactam) extends spectrum

Piperacillin/tazobactam

Increased prevalence of b -lactamase producing bacteria over past few years has resulted in increased resistance to piperacillin. Addition of tazobactam, a b lactamase inhibitor, restores and extends its anti-bacterial cover.

Pharmacokinetics

  • IV administration
  • Both piperacillin and tazobactam are widely distributed. Penetration into biliary tree is good
  • 50-60% excreted via kidneys. Decrease dose in patients with creatinine clearance <20ml/min. Haemofiltered patients should receive piperacillin/tazobactam twice daily and an additional dose of piperacillin alone once daily.
  • Pharmacokinetics are unaltered in patients with hepatic impairment

Spectrum of activity

Good in vitro activity against:

  • Methicillin sensitive Staph. aureus
  • Methicillin sensitive coagulase negative staphylococci
  • Streptococcus pyogenes and penicillin-sensitive S. pneumoniae
  • Enterobacteriaceae including E. coli, Klebsiella spp., Enterobacter spp.
  • Haemophiluse influenzae, Moraxella catarrhalis
  • P. aeruginosa
  • Anaerobes including Bacteroides spp. and Clostridium spp.
  • Enterococcus faecalis (but not E. faecium)

The following are resistant:

  • MRSA and many methicillin resistant coagulase negative staphylococci
  • Stenotrophomonas maltophilia
  • Enterococcus faecium

Clinical uses

Empirical therapy for

  • Nosocomial pneumonia
  • Intra-abdominal infection
  • Neutropaenic fever

Adverse effects

Generally well tolerated. Most frequent adverse effects are GI symptoms (most commonly diarrhoea) and skin reactions. Side effects are more common when given with an aminoglycoside.

Potential conflict of interest

The Dept of Anaesthesia & Intensive Care, The Chinese University of Hong Kong received sponsorship for educational activities from Wyeth (HK) Ltd  in 2002 and 2003


 

©Charles Gomersall, April, 2014 unless otherwise stated. The author, editor and The Chinese University of Hong Kong take no responsibility for any adverse event resulting from the use of this webpage.
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