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Spectrum of activity
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Class
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Example
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Antimicrobial spectrum
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Natural penicillins
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Benzylpenicillin
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Gm +ves, anaerobes and selected Gm -ves
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Penicillinase resistant penicillins
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Flucloxacillin, cloxacillin
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Penicillin-resistant staphylococci.
Also active against streptococci
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Aminopenicillins
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Amoxycillin, ampicillin
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As for penicillin G plus Gram
–ve cocci, and Enterobacteriaceae. The addition of b
lactamase inhibitors expands the Gram +ve, -ve and anaerobic spectrum
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Carboxypenicillins
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Carbenicillin, ticarcillin
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As for aminopenicillins plus Gm
–ve rods resistant to ampicillin, including P. aeruginosa.
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Ureidopenicillins
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Piperacillin, azlocillin
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Similar to carboxypenicillins.
Addition of ß lactamase inhibitor (as in piperacillin/tazobactam) extends
spectrum
|
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
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