A1,
A2,
B,
C1,
C2,
D,
E,
F,
G-H,
I-K,
L,
M,
N,
O,
P1,
P2,
Q-R,
S,
T,
U-V,
W-Z
Bactocill Pharmacology, Pharmacokinetics, Studies, Metabolism - Oxacillin Sodium
Bactocill Pharmacology, Pharmacokinetics, Studies, Metabolism - Oxacillin Sodium
CLINICAL PHARMACOLOGY
Microbiology
Penicillinase-resistant penicillins exert a bactericidal
action against penicillin-susceptible
microorganisms during the state
of active multiplication. All penicillins inhibit the biosynthesis
of the bacterial cell wall.
The drugs in this class
are highly resistant to inactivation
by staphylococcal penicillinase and are active against penicil-linase-producing
and non penicillinase-producing strains of Staphylococcus aereus.
The penicillinase-resistant penicillins are active in vitro
against a variety of other bacteria.
Susceptibility Plate Testing
Quantitative methods of susceptibility testing that require measurement
of zone diameters or minimal
inhibitory concentrations (MIC's) give the most precise estimates
of antibiotic susceptibility.
One such procedure has been recommended for use with discs to test
susceptibility to this class of drugs. Interpretations correlate
diameters on the disc test
with MIC values. A penicillinase-resistant class
disc may be used to determine
microbial susceptibility to cloxacillin dicloxacillin, methicillin,
nafcillin and oxacillin. With this procedure, employing a 5 micro-gram
methicillin sodium disc, a report
from the laboratory of ''susceptible'' (zone of at least 14 mm)
indicates that the infecting organism
is likely to respond to therapy. A report
of "resistant'' (zone of less than 10 mm) indicates that the
infecting organism
is not likely to respond to therapy. A report of ''intermediate
susceptibility'' (zone of 10 to 13 mm) suggests that the organism
might be susceptible
if high doses of the antibiotic
are used, or if the infection
is confined to tissues and fluids (eg, urine), in which high antibiotic
levels are attained.
In general all staphylococci
should be tested against the penicillin G disc
and against the methicillin disc. Routine methods of antibiotic
susceptibility testing may fail to detect strains of organisms resistant
to the penicillinase-resistant penicillins. For this reason the
use of large inocula and 48-hour incubation
periods may be necessary to obtain accurate susceptibility studies
with these antibiotics. Bacterial strains which are resistant to
one of the penicillinase-resistant penicillins should be considered
resistant to all of the drugs in the class.
PHARMACOKINETICS
Oxacillin Sodium, with normal
doses, has insignificant concentrations in the cerebrospinal
and ascitic fluids. It is found in therapeutic
concentrations in the pleural, bile, and amniotic fluids. Oxacillin
Sodium is rapidly excreted as unchanged drug
in the urine by glomerular
filtration and active
tubular secretion.
Oxacillin Sodium binds to serum
protein, mainly albumin. The degree of protein
binding reported varies with the method
of study and the investigator but generally has been found to be
94.2 ± 2.1%.
Intramuscular injections give peak serum
levels 30 minutes after injection. A 250 mg
dose gives a level of 5.3
µg/mL while a 500 mg
dose peaks at 10.9 µg/mL.
Intravenous injection
gives a peak about 5 minutes after the injection
is completed. Slow IV dosing
with 500 mg gives a 5 minute
peak of 43 µg/mL with a half-life
of 20 to 30 minutes.
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