β lactam antibiotic
Binds to penicillin binding protein (transpeptidase) and
prevents crosslinking of bacterial peptidoglycan
impairs cell wall synthesis

Beta lactam ring binds to penicillin binding protein (transpeptidase) and
prevents crosslinking of bacterial peptidoglycan
inhibits cell wall synthesis

Bacteria eventually lyse due to ongoing activity of cell wall autolytic enzymes (autolysins and murein hydrolases) while cell wall assembly is arrested

Less bactericidal but stable to staph beta-lactamases

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

Orally not absorbed (need penicillin V)

bioavailabilty 50–70%
routes of administration PO, IV or IM
doses Usually given QID or TDS in up to 2g/day

BA 62%

CSF and bone penetration if inflammation present

penetration into CSF occurs with inflamed meninges only

penetration into CSF occurs with inflamed meninges only

60% PB

up to 95% PB

20% PB

Vd <1L/kg

Vd ~0.28 L/kg

Inactive metabolite penicollic acid

Hepatic- active metab

Some Hepatic Metabolism

90% excreted in urine by tubular secretion
25% unchanged

excretion Urine (50-65% as unchanged drug)

Mostly unchanged in urine.
Rest is feces and bile

half life 0.75–1 hours, prolonged in anuria/renal impair

GIT– abdominal pain, N/V/D, pseudomembranous colitis, hepatitis
HAEM- agranulocytosis
CNS- confusion, seizure, encephalopathy
HYPERSENSITIVITY- rash, anaphylaxis

Up to 10% of the population have allergies to penicillins. Due to the high
percentage excreted renally unchanged dose adjustment is required in low urine
output states. Severe cholestatic hepatitis has been reported idiosyncratically.

Narrow-Spectrum
Natural Penicillin

Highly bactericidal, only
gram positives/anaerobes,
susceptible to betalactamases

Targets
GPC: Streptococci, Meningococcus
Listeria (GPB)
GNC: Neisseria, Clostridia
Treponemma (Spiral)

Synergistic effects with
aminoglycosides

narrow spectrum but is
useful for treating staphlococci which are resistant to benpen due to beta-lactamase activity
It should not be used if the organism is sensitive to benpen as benpen is more bactericidal

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

ANTIBIOTIC:
PENICILLIN

ANTIBIOTIC:
PENICILLIN

ANTIBIOTIC:
PENICILLIN

useful for treating staphlococci which are resistant to benpen due to beta-lactamase activity
. It is well absorbed from the gut but is given IV if the infection is serious. It should not be used if the organism is sensitive to benpen as
benpen is more bacteriocidal.

Narrow spectrum naturally occurring penicillin

Narrow spectrum, semisynthetic anti-staphylococcal penicillin

Betalactam

Level 1

Level 1

Level 1

PO/IV. Tablet/Powder for reconstitution

Resistance
MRSA
Many Staph
-Betalactamase prod
Gram Negatives

MRSA develop or acquire the gene mecA which synthesizes an additional penicillin binding protein that enables it to continue cell wall synthesis in the presence of a beta lactam drug

Bacteria produce beta lactamases, which hydrolyse and inactivate the antibiotic

Resistance
MRSA
Many Staph
-Betalactamase prod