CLINICAL PHARMACOLOGY
Intravenous Administration:
In healthy adult volunteers, mean serum piperacillin concentrations immediately
after a two-to three-minute intravenous injection of 2, 4, or 6 g were 305,
412, and 775 μg/mL, respectively. Serum concentrations lack dose proportionality.
PIPERACILLIN SERUM CONCENTRATIONS IN ADULTS (μg/mL) AFTER
A TWO-TO THREE-MINUTE I.V. INJECTION
DOSE |
0 |
10min |
20min |
30min |
1 h |
1.5 h |
2 h |
3 h |
4 h |
6 h |
8 h |
2 |
305
(159-615) |
202
(164-225) |
156
(52-165) |
67
(41-88) |
40
(25-57) |
24
(18-31) |
20
(14-24) |
8
(3-11) |
3
(2-4) |
2
(=0.6-3) |
- |
4 |
412
(389-484) |
344
(315-379) |
295
(269-330) |
117
(98-138) |
93
(78-110) |
60
(50-67) |
36
(26-51) |
20
(17-24) |
8
(7-11) |
4
(3.7-4.1) |
0.9
(0.7-1) |
6 |
775
(695-849) |
609
(530-670) |
563
(492-630) |
325
(292-363) |
208
(180-239) |
138
(115-175) |
90
(71-113) |
38
(29-53) |
33
(25-44) |
8
(3-19) |
3.2( < 2-6) |
PIPERACILLIN SERUM CONCENTRATIONS IN ADULTS (μg/mL) AFTER
A 30-MINUTE I.V. INFUSION
DOSE |
0 |
5min |
10min |
15min |
30min |
45min |
1 h |
1.5h |
2 h |
4 h |
6 h |
7.5h |
4 |
244
(155-298) |
215
(169-247) |
186
(140-209) |
177
(142-213) |
141
(122-156) |
146
(110-265) |
105
(85-133) |
72
(53-105) |
53
(36-69) |
15
(6-24) |
4
(1-9) |
2
(0.5-3) |
6 |
353
(324-371) |
298
(242-339) |
298
(232-331) |
272
(219-314) |
229
(185-249) |
180
(144-209) |
149
(117-171) |
104
(89-113) |
73
(66-94) |
22
(12-39) |
16
(5-49) |
-- |
A 30-minute infusion of 6 g every 6 h gave, on the fourth day, a mean peak
serum concentration of 420 μg/mL.
Intramuscular Administration
PIPRACIL (piperacillin sodium) is rapidly absorbed after intramuscular injection. In healthy volunteers,
the mean peak serum concentration occurs approximately 30 minutes after a single
dose of 2 g and is about 36 μg/mL. The oral administration of 1 g probenecid
before injection produces an increase in piperacillin peak serum level of about
30%. The area under the curve (AUC) is increased by approximately 60%.
Pharmacokinetics
PIPRACIL (piperacillin sodium) is not absorbed when given orally. Peak serum concentrations are attained
approximately 30 minutes after intramuscular injections and immediately after
completion of intravenous injection or infusion. The serum half-life in healthy
volunteers ranges from 36 minutes to one hour and 12 minutes. The mean elimination
half-life of PIPRACIL (piperacillin sodium) in healthy adult volunteers is 54 minutes following administration
of 2 g and 63 minutes following 6 g. As with other penicillins, PIPRACIL (piperacillin sodium) is
eliminated primarily by glomerular filtration and tubular secretion; it is excreted
rapidly as unchanged drug in high concentrations in the urine. Approximately
60% to 80% of the administered dose is excreted in the urine in the first 24
hours. Piperacillin urine concentrations, determined by microbioassay, are as
high as 14,100 μg/mL following a 6-g intravenous dose and 8,500 μg/mL
following a 4-g intravenous dose. These urine drug concentrations remain well
above 1,000 μg/mL throughout the dosing interval.
Distribution
PIPRACIL (piperacillin sodium) binding to human serum proteins is 16%. The drug is widely distributed
in human tissues and body fluids, including bone, prostate, and heart, and reaches
high concentrations in bile. After a 4-g bolus injection, maximum biliary concentrations
average 3,205 μg/mL. It penetrates into the cerebrospinal fluid in the presence
of inflamed meninges.
Special Populations
Renal Insufficiency: The elimination half-life is increased twofold
in mild to moderate renal impairment and fivefold to sixfold in severe impairment.
Because PIPRACIL (piperacillin sodium) is excreted by the biliary route as well as by the renal route,
it can be used safely in appropriate dosage in patients with severely restricted
kidney function. (See DOSAGE AND ADMINISTRATION.)
Pediatric Patients: After intravenous administration of 50 mg/kg
(5-minute infusion) in neonates, the mean plasma concentration of piperacillin
extrapolated to time zero was 141 μg/mL, and the apparent volume of distribution
averaged 101 mL/kg.
In premature neonates, the mean elimination half-life has been reported to
range from 147 to 258 minutes following administration of a single intravenous
dose of 75 mg/kg, the half-life decreasing with increasing postnatal age. The
changes in half-life appeared to be caused by an immature renal system during
the first weeks of life. In one study in neonates, the mean elimination half-life
ranged from 127 to 217 minutes following a single intravenous dose of 50 mg/kg.
As in premature neonates, the half-life in neonates decreased with increasing
postnatal age. The mean total body clearance in neonates has been reported to
range from 32 to 41 mL/min/1.73 m²after an intravenous dose of 50 mg/kg.
Following administration of an intravenous dose of 50 mg/kg in older pediatric
patients (from 1 month up to 15 years of age), the mean elimination half-life
has been reported to range from 31 to 37 minutes, and the mean total body clearance
has been reported to range from 124 to 160 mL/min/1.73 m².
As in adults, PIPRACIL (piperacillin sodium) elimination tends to be prolonged in pediatric patients
with renal impairment. In one study in pediatric patients (age range, 3.3 to
14.3 years), the mean elimination half-life in patients with decreased renal
function was approximately 60 minutes versus 37 minutes in patients with normal
renal function. The elimination half-life has been reported to range from 3.5
to 14 hours in neonates with severe renal impairment.
Pharmacokinetic data have indicated that among pediatric patients below 12
years of age, those with cystic fibrosis have increased bioavailability, lower
serum concentrations, and increased total body clearance of piperacillin compared
to young, healthy pediatric volunteers under 12 years of age.
Microbiology
Piperacillin is an antibiotic which exerts its bactericidal activity by inhibiting
both septum and cell wall synthesis. It is active against a variety of gram-positive
and gram-negative aerobic and anaerobic bacteria. Piperacillin has been shown
to be active against most strains of the following microorganisms, both in
vitro and in clinical infections as described in the INDICATIONS
AND USAGE section.
Aerobic gram-positive microorganisms
Enterococci, including
Enterococcus faecalis
Streptococcus pneumoniae
Streptococcus pyogenes
Aerobic gram-negative microorganisms
Acinetobacter species
Enterobacter species
Escherichia coli
Haemophilus influenzae (non-β-lactamase-producing strains)
Klebsiellaspecies
Morganella morganii
Neisseria gonorrhoeae
Proteus mirabilis
Proteus vulgaris
Providencia rettgeri
Pseudomonas aeruginosa
Serratia species
Anaerobic gram-positive microorganisms
Anaerobic cocci
Clostridiumspecies
Anaerobic gram-negative microorganisms
Bacteroides species, including Bacteroides fragilis
The following in vitro data are available, but their clinical significance
is unknown.
At least 90% of the following microorganisms exhibit an in vitro minimum
inhibitory concentration (MIC) less than or equal to the susceptible breakpoint
for piperacillin. However, the safety and effectiveness of piperacillin in treating
clinical infections due to these microorganisms have not been established in
adequate and well-controlled clinical trials.
Aerobic gram-positive microorganisms
Streptococcus agalactiae
Streptococcus bovis
Viridans group streptococci
Aerobic gram-negative microorganisms
Burkholderia cepacia
Citrobacter diversus
Citrobacter freundii
Pseudomonas fluorescens
Stenotrophomonas maltophilia
Yersinia enterocolitica
Anaerobic gram-positive microorganisms
Actinomyces species
Eubacterium species
Anaerobic gram-negative microorganisms
Fusobacterium necrophorum
Fusobacterium nucleatum
Porphyromonas asaccharolytica
Prevotella melaninogenica
Veillonella species
Susceptibility Testing Methods
Dilution Techniques
Quantitative methods are used to determine antimicrobial minimum inhibitory
concentrations (MICs). These MICs provide estimates of the susceptibility of
bacteria to antimicrobial compounds. The MICs should be determined using a standardized
procedure. Standardized procedures are based on a dilution method1,2 (broth
or agar) or equivalent with standardized inoculum concentrations and standardized
concentrations of piperacillin powder. The MIC values should be interpreted
according to the following criteria:
For testing Enterobacteriaceae and Acinetobacter species:
MIC (μg/mL) |
Interpretation |
≤ 16 |
Susceptible (S) |
32-64 |
Intermediate (I) |
≥ 128 |
Resistant (R) |
For testing Pseudomonas aeruginosa:
MIC (μg/mL) |
Interpretation |
≤ 64 |
Susceptible (S) |
≥ 128 |
Resistant (R) |
For testing Enterococcus faecalisa:
MIC (μg/mL) |
Interpretation |
≤ 8 |
Susceptible (S) |
≥ 16 |
Resistant (R) |
aPenicillin susceptibility may
be used to predict the susceptibility to piperacillin.1,2 |
Haemophilus species are considered susceptible if the MIC of piperacillin
is ≤ to 1 μg/mL.*
* Dilution methods such as those described in the International Collaborative
Study (Acta Pathol Microbiol Scand [B] 1971; suppl 217) have been used to determine
susceptibility of organisms to piperacillin.
Dilution (MICs) susceptibility test methods and interpretative criteria for
assessing the susceptibility of Neisseria gonorrhoeae to piperacillin
have not been established. However, β-lactamase testing will detect one
form of penicillin resistance in Neisseria gonorrhoeae and is recommended.1,2
Dilution (MICs) susceptibility test methods and interpretative criteria
for assessing the susceptibility of Streptococcus pneumoniae and Streptococcus
pyogenes to piperacillin have not been established.1,2
A report of “Susceptible” indicates that the pathogen is likely
to be inhibited if the antimicrobial compound in the blood reaches the concentrations
usually achievable. A report of “Intermediate” indicates that the
result should be considered equivocal, and, if the microorganism is not fully
susceptible to alternative, clinically feasible drugs, the test should be repeated.
This category implies possible clinical applicability in body sites where the
drug is physiologically concentrated or in situations where high dosage of drug
can be used. This category also provides a buffer zone which prevents small
uncontrolled technical factors from causing major discrepancies in interpretation.
A report of “Resistant” indicates that the pathogen is not likely
to be inhibited if the antimicrobial compound in the blood reaches the concentrations
usually achievable; other therapy should be selected.
Quality Control
Standardized susceptibility test procedures require the use of laboratory control
microorganisms to control the technical aspects of the laboratory procedures.
Standard piperacillin powder should provide the following MIC values:
Microorganism |
|
MIC (μg/mL) |
Enterococcus faecalis |
ATCC 29212 |
1-4 |
Escherichia coli |
ATCC 25922 |
1-4 |
Pseudomonas aeruginosa |
ATCC 27853 |
1-8 |
Diffusion Techniques
Quantitative methods that require measurement of zone diameters also provide
reproducible estimates of the susceptibility of bacteria to antimicrobial compounds.
One such standardized procedure2,3 requires the use of standardized
inoculum concentrations. This procedure uses paper disks impregnated with 100
μg of piperacillin to test the susceptibility of microorganisms to piperacillin.
Reports from the laboratory providing results of the standard single-disk susceptibility
test with a 100 μg piperacillin disk should be interpreted according to the
following criteria:
For testing Enterobacteriaceae and Acinetobacter species:
Zone Diameter (mm) |
Interpretation |
≥ 21 |
Susceptible (S) |
18-20 |
Intermediate (I) |
≤ 17 |
Resistant (R) |
For testing Pseudomonas aeruginosa:
Zone Diameter (mm) |
Interpretation |
≥ 18 |
Susceptible (S) |
≤ 17 |
Resistant (R) |
For testing Enterococcus faecalisb:
Zone Diameter (mm) |
Interpretation |
≥ 15 |
Susceptible (S) |
≤ 14 |
Resistant (R) |
bPenicillin susceptibility may
be used to predict the susceptibility to piperacillin.2,3 |
Haemophilus species which give zones of ≥ 29 mm are susceptible;
resistant strains give zones of ≤ 28 mm. The above interpretive criteria
are based on the use of the standardized procedure. Antibiotic susceptibility
testing requires carefully prescribed procedures. Susceptibility tests are biased
to a considerable degree when different methods are used.
NCCLS Approved Standard; M2-A2 (Formerly ASM-2) Performance Standards for Antimicrobic
Disk Susceptibility Tests, Second Edition, available from the National Committee
of Clinical Laboratory Standards.
Disk diffusion (zone diameters) susceptibility test methods and interpretative
criteria for assessing the susceptibility of Neisseria gonorrhoeae to
piperacillin have not been established. However, β-lactamase testing to
penicillin is recommended. It will detect one form of penicillin resistance,
chromosomally mediated resistance, in Neisseria gonorrhoeae. In addition,
gonococci with 10-unit penicillin disk zone diameters of ≤ 19 mm are likely
to be β-lactamase producing strains (plasmid-mediated penicillin resistance).2,3
Disk diffusion (zone diameters) susceptibility test methods and interpretative
criteria for assessing the susceptibility of Streptococcus pneumoniae and
Streptococcus pyogenes to piperacillin have not been established.2,3
Interpretation should be as stated above for results using dilution techniques.
Interpretation involves correlation of the diameter obtained in the disk test
with the MIC for piperacillin.
Quality Control
As with standardized dilution techniques, diffusion methods require the use
of laboratory control microorganisms that are used to control the technical
aspects of the laboratory procedures. For the diffusion technique, the 100-μg
piperacillin disk should provide the following zone diameters in these laboratory
test quality control strains:
Microorganism |
|
Zone Diameter (mm) |
Escherichia coli |
ATCC 25922 |
24-30 |
Pseudomonas aeruginosa |
ATCC 27853 |
25-33 |
Anaerobic Techniques
For anaerobic bacteria, the susceptibility to piperacillin as MICs can be determined
by standardized test methods.4 The MIC values obtained should be
interpreted according to the following criteria:
MIC (μg/mL) |
Interpretation |
≤ 32 |
Susceptible (S) |
64 |
Intermediate (I) |
≥ 128 |
Resistant (R) |
Interpretation is identical to that stated above for results using dilution
techniques.
As with other susceptibility techniques, the use of laboratory control microorganisms
is required to control the technical aspects of the laboratory standardized
procedures. Standardized piperacillin powder should provide the following MIC
values:
Microorganism |
|
MIC (μg/mL) |
Bacteroides fragilisc |
ATCC 25285 |
2-8 |
Bacteroides thetaiotaomicrond |
ATCC 29741 |
8-32 |
c This quality control range is
applicable only to tests performed using either Brucella blood
agar or Wilkins-Chalgren agar with the Reference Agar Dilution Method.4
d This quality range is applicable only to tests performed in the
broth formulation of Wilkins-Chalgren agar with the Broth microdilution
method.4 |
REFERENCES
1 National Committee for Clinical Laboratory Standards.
Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow
Aerobically - Fifth Edition. Approved Standard NCCLS Document M7-A5, Vol. 20,
No. 2, NCCLS, Wayne, PA, January, 2000.
2 National Committee for Clinical Laboratory Standards.
Performance Standards for Antimicrobial Susceptibility Testing - Eleventh Informational
Supplement. NCCLS Document M100-S11, Vol. 21, No. 1, NCCLS, Wayne, PA, January,
2001.
3 National Committee for Clinical Laboratory Standards.
Performance Standards for Antimicrobial Disk Susceptibility Tests - Seventh
Edition. Approved Standard NCCLS Document M2-A7, Vol. 20, No. 1, NCCLS, Wayne,
PA, January, 2000.
4 National Committee for Clinical Laboratory Standards.
Methods for Antimicrobial Susceptibility Testing of Anaerobic Bacteria - Fifth
Edition. Approved Standard NCCLS Document M11-A5, Vol. 21, No. 2, NCCLS, Wayne,
PA, March, 2001.