Contains a beta lactam ring structure. Betalactam antibiotics inhibit the growth of sensitive bacteria by inactivating transpeptidase enzymes located in the bacterial cell membrane, inhibiting crosslinkage of peptidoglycans and thus impairing cell wall synthesis

bactericidal

Binds to the bacterial 30S ribosomal subunit to inhibit protein synthesis and thus bacterial growth

Bacteriocidal antimicrobials that block DNA replication by blocking tropoisomerase enzymes, which are essential for the supercoiling, replication and separation of circular bacterial DNA

BA 62%

BA no oral absorption, rapid and complete IM.
IV (poor lipid solubility)
doses 3-10mcg/kg depending on severity
onset / duration 30mins

Good oral absorption (80%)

Undergoes first pass

Coadministration of calcium or magnesium reduces absorption

penetration into CSF occurs with inflamed meninges only

lip sol low - reduces gut absorption
some CSF penetration with inflamed meninges (30%)

High CSF and tissue penetration

20% PB

<30% PB

30% PB

Vd 0.2-0.3 L/kg

Vd 2-3L/kg

Some Hepatic Metabolism

not metabolised

Little hepatic metabolism

Mostly unchanged in urine.
Rest is feces and bile

excretion urine as unchanged drug

Active tubular secretion

half life 1.5-3 hrs, +++ in renal impairment (up to 70hrs)

T1/2= 3 hours (renal dose adjustment required)

ototoxicity
nephrotoxicity (worse with loop diuretics or pre-existing renal disease)
pre-jn Ach release   post-jn sensitivity to Ach NMBD activity can cause paralysis.

May cause C.Diff.

1. CNS Toxicity- GABA antagonists and may precipitate seizures in epileptic patients, particularly in presence of NSAIDs
2. Tendonitis and tendon rupture
3. QT prolongation- Low risk of Torsade’s in absence of other predisposing factors
4. Hemolysis in G6PD
5. Photosensitivity
6. Arthralgias and cartilage toxicity (generally avoided in children)
7. Dysglycaemia (hyper and hypoglycaemia)

Moderate spectrum
Semisynthetic
Can penetrate some gram
negative outer membranes,
but susceptible to betalactamases. Often given with clauvanic acid
Targets
Strep, Listeria, Enterococcus, Haemophilus

provide good gram negative coverage and some gram positive
most often used against enteric infections and in sepsis
usually used in combination with a beta lactam

Broad spectrum
Active against both gram positive and gram negative bacteria

particularly effective against
GNB (E.Coli, H.influenza, Klebsiella, Legionella, Moraxella, Proteus, and Pseudomonas)
Less effective against Gram-positive bacteria (such as MSSA, Strep pneumoniae, and Enterococcus faecalis) than newer fluoroquinolones

ANTIBIOTIC:
PENICILLIN

ANTIBIOTIC:
AMINOGLYCOSIDE

ANTIBIOTIC:
QUINOLONE

aminoglycoside of choice because of its lower cost and reliable activity against GNB.
It is often used in combination
with a beta lactam antibiotic for serious but uncultured infections. They also have
limited gram positive coverage including staph and some strep

Betalactam

Aminoglycoside

Quinolone

Level 1

Level 1

Level 3

Level 1

clear solution for injection. Requires monitoring of levels especially
if there is any renal impairment, to prevent complications

PO and IV, topical eye drops and ointment

Bacteria produce beta lactamases, which hydrolyse and inactivate the antibiotic

Resistance
MRSA
Many Staph
-Betalactamase prod

Alteration in access to target site – membrane impermeability / transport defect in the active transport.
Lack of O2-transport channels: Anaerobes
Multiple enzymes which block gentamicin (acetytransferases, adenyltransferases, phosphotransferases)

Alteration in target enzyme – changes to the DNA binding surface of DNA supergyrase infers resistance
Alteration in drug entry – altered expression of outer membrane porin proteins that form channels for passive diffusion of ciprofloxacin
Increase in efflux of drug – expression of nonspecific energy dependent efflux pumps which remove drug