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

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%

Good oral absorption (80%)

Undergoes first pass

Coadministration of calcium or magnesium reduces absorption

penetration into CSF occurs with inflamed meninges only

High CSF and tissue penetration

20% PB

30% PB

Vd 2-3L/kg

Some Hepatic Metabolism

Little hepatic metabolism

Mostly unchanged in urine.
Rest is feces and bile

Active tubular secretion

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

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

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:
QUINOLONE

Betalactam

Quinolone

Level 1

Level 3

Level 1

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 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