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

Converted to active form or nitroso free radical by
obligate anaerobes. Inhibits DNA synthesis. Causes DNA degradation

Orally not absorbed (need penicillin V)

50% PO BA
75% Rectal BA

CSF and bone penetration if inflammation present

Widely distributed to all tissues

60% PB

10% PB

Vd <1L/kg

Vd 0.75 L/kg

Inactive metabolite penicollic acid

Hepatic Oxidation and glucuronidation

90% excreted in urine by tubular secretion
25% unchanged

Renal excretion 60% unchanged

T1/2 = 6-10hrs
Renal dose adjustment not required

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

GIT– abdominal pain, N/V/D,
jaundice, pancreatitis
HAEM- leukopenia
CVS– T wave flattening, QT
prolongation
CNS– ataxia, seizures, insomnia, paraesthesia
HYPERSENSITIVITY– rash
OTHER– metallic taste

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

Active against anaerobes (including clostridium, N.Gonorrhoea, N.Menigitidis, Bacterioides and Fusobacterium) and protozoa
(trichomonas, Giardia)

ANTIBIOTIC:
PENICILLIN

ANTIBIOTIC:
NITROIMIDAZOLE

Narrow spectrum naturally occurring penicillin

Nitroimidazole

Level 1

Level 3

Resistance
MRSA
Many Staph
-Betalactamase prod
Gram Negatives

reduced rate of uptake, by efflux or by reducing the rate of metronidazole reductive activation
increased DNA repair efficiency