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

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

CSF and bone penetration if inflammation present

penetration into CSF occurs with inflamed meninges only

60% PB

up to 95% PB

Vd <1L/kg

Vd ~0.28 L/kg

Inactive metabolite penicollic acid

Hepatic- active metab

90% excreted in urine by tubular secretion
25% unchanged

excretion Urine (50-65% as unchanged drug)

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

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

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