Human Pharmacology
Serum level studies with a
150 mg oral dose of clindamycin hydrochloride in 24 normal adult volunteers
showed that clindamycin was rapidly absorbed after oral administration. An
average peak serum level of 2.5 mcg/mL was reached in 45 minutes; serum levels
averaged 1.51 mcg/mL at 3 hours and 0.7 mcg/mL at 6 hours. Absorption of an oral
dose is virtually complete (90%), and the concomitant administration of food
does not appreciably modify the serum concentrations; serum levels have been
uniform and predictable from person to person and dose to dose. Serum level
studies following multiple doses of clindamycin hydrochloride for up to 14 days
show no evidence of accumulation or altered metabolism of drug.
Serum
half-life of clindamycin is increased slightly in patients with markedly
reduced renal function. Hemodialysis and peritoneal dialysis are not effective
in removing clindamycin from the serum.
Concentrations of clindamycin in
the serum increased linearly with increased dose. Serum levels exceed the MIC
(minimum inhibitory concentration) for most indicated organisms for at least six
hours following administration of the usually recommended doses. Clindamycin is
widely distributed in body fluids and tissues (including bones). The average
biological half-life is 2.4 hours. Approximately 10% of the bioactivity is
excreted in the urine and 3.6% in the feces; the remainder is excreted as
bioinactive metabolites.
Doses of up to 2 grams of clindamycin per day
for 14 days have been well tolerated by healthy volunteers, except that the
incidence of gastrointestinal side effects is greater with the higher
doses.
No significant levels of clindamycin are attained in the
cerebrospinal fluid, even in the presence of inflamed
meninges.
Pharmacokinetic studies in elderly volunteers (61 to 79 years)
and younger adults (18 to 39 years) indicate that age alone does not alter
clindamycin pharmacokinetics (clearance, elimination half-life, volume of
distribution, and area under the serum concentration-time curve) after IV
administration of clindamycin phosphate. After oral administration of
clindamycin hydrochloride, elimination half-life is increased to approximately 4
hours (range 3.4 to 5.1 h) in the elderly compared to 3.2 hours (range 2.1 to
4.2 h) in younger adults. The extent of absorption, however, is not different
between age groups and no dosage alteration is necessary for the elderly with
normal hepatic function and normal (age-adjusted) renal function.
Microbiology
Clindamycin inhibits bacterial
protein synthesis by binding to the 50S subunit of the ribosome. It has activity
against Gram-positive aerobes and anaerobes as well as the Gram-negative
anaerobes. Clindamycin is bacteriostatic. Cross-resistance between clindamycin
and lincomycin is complete. Antagonism
in vitro has
been demonstrated between clindamycin and erythromycin.
Clindamycin has
been shown to be active against most of the isolates of the following
microorganisms, both
in vitro and in clinical
infections, as described in the
INDICATIONS AND USAGE section.
Gram-positive aerobes
Staphylococcus aureus (methicillin-susceptible
strains)
Streptococcus pneumoniae
(penicillin-susceptible strains)
Streptococcus
pyogenes
Anaerobes
Prevotella melaninogenica
Fusobacterium necrophorum
Fusobacterium nucleatum
Peptostreptococcus anaerobius
Clostridium perfringens
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 clindamycin. However, the safety
and effectiveness of clindamycin in treating clinical infections due to these
microorganisms have not been established in adequate and well-controlled
clinical trials.
Gram-positive aerobes
Staphylococcus epidermidis
(methicillin-susceptible strains)
Streptococcus
agalactiae
Streptococcus anginosus
Streptococcus oralis
Streptococcus
mitis
Anaerobes
Prevotella intermedia
Prevotella
bivia
Propionibacterium acnes
Micromonas (“Peptostreptococcus”)
micros
Finegoldia (“Peptostreptococcus”) magna
Actinomyces
israelii
Clostridium clostridioforme
Eubacterium lentum
Susceptibility Testing Methods
NOTE: Susceptibility testing by dilution methods requires
the use of clindamycin susceptibility powder.
When available, the
results of
in vitro susceptibility tests should be
provided to the physician as periodic reports that describe the susceptibility
profile of nosocomial and community-acquired pathogens. These reports should aid
the physician in selecting the most effective antimicrobial.
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 method (broth and agar)
1,2,3 or equivalent
with standardized inoculum concentrations and standardized concentrations of
clindamycin powder. The MIC values should be interpreted according to the
criteria provided in Table 1.
Diffusion Techniques
Quantitative
methods that require the measurement of zone diameters also provide reproducible
estimates of the susceptibility of bacteria to antimicrobial compounds. One such
standardized procedure
2,3 requires the use of
standardized inoculum concentrations. This procedure uses paper disks
impregnated with 2 mcg of clindamycin to test the susceptibility of
microorganisms to clindamycin. The disk diffusion interpretive criteria are
provided in Table 1.
a These
interpretive standards for
S. pneumoniae and other
Streptococcus spp. are applicable only to tests
performed by broth microdilution using cation-adjusted Mueller-Hinton broth with
2 to 5% lysed horse blood inoculated with a direct colony suspension and
incubated in ambient air at 35°C for 20 to 24 hours.
b
These zone diameter interpretive standards are applicable only to tests
performed using Mueller-Hinton agar supplemented with 5% sheep blood inoculated
with a direct colony suspension and incubated in 5% CO
2
at 35°C for 20 to 24 hours.
c These interpretive
criteria are for all anaerobic bacterial pathogens; no organism specific
interpretive criteria are available.
NA=Not applicable
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 that 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 quality control microorganisms to control the
technical aspects of the test procedures. Standard clindamycin powder should
provide the following range of values noted in Table 2.
NOTE:
Quality control microorganisms are specific strains of organisms with
intrinsic biological properties relating to resistance mechanisms and their
genetic expression within bacteria; the specific strains used for
microbiological quality control are not clinically significant.
NA=Not applicable
d This organism may be used for validation of susceptibility
test results when testing
Streptococcus spp. other
than
S. pneumoniae.
e This
quality control range for
S. pneumoniae is applicable
only to tests performed by broth microdilution using cation-adjusted
Mueller-Hinton broth with 2 to 5% lysed horse blood inoculated with a direct
colony suspension and incubated in ambient air at 35°C for 20 to 24
hours.
f This quality control zone diameter range is
applicable only to tests performed using Mueller-Hinton agar supplemented with
5% sheep blood inoculated with a direct colony suspension and incubated in 5%
CO
2 at 35°C for 20 to 24 hours.
ATCC
® is a registered trademark of the American Type Culture
Collection
INDICATIONS AND USAGE
Clindamycin
hydrochloride capsules are indicated in the treatment of serious infections
caused by susceptible anaerobic