August 3, 2015
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Minocin

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Minocin




CLINICAL PHARMACOLOGY

Following a single dose of two 100 mg minocycline HCl powder-filled capsules administered to ten normal adult volunteers, serum levels ranged from 0.74 to 4.45 μg/mL in 1 hour (average 2.24); after 12 hours they ranged from 0.34 to 2.36 μg/mL (average 1.25). The serum half-life following a single 200 mg dose in 12 essentially normal volunteers ranged from 11 to 17 hours. In seven patients with hepatic dysfunction it ranged from 11 to 16 hours, and in 5 patients with renal dysfunction it ranged from 18 to 69 hours. The urinary and fecal recovery of minocycline when administered to 12 normal volunteers was one-half to one-third that of other tetracyclines.

Microbiology

Mechanism of Action

The tetracyclines are primarily bacteriostatic and are thought to exert their antimicrobial effect by the inhibition of protein synthesis. The tetracyclines, including minocycline, have a similar antimicrobial spectrum of activity against a wide range of gram-positive and gram-negative organisms. Cross-resistance of these organisms to tetracycline is common.

List of Microorganisms

Minocycline 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:

Gram-positive Bacteria

Bacillus anthracis
Listeria monocytogenes

Staphylococcus aureus

Streptococcus pneumoniae

Gram-negative Bacteria

Bartonella bacilliformis
Brucella
species
Klebsiella granulomatis

Campylobacter fetus

Francisella tularensis

Haemophilus ducreyi

Vibrio cholerae

Yersinia pestis

Acinetobacter
species
Enterobacter aerogenes

Escherichia coli

Haemophilus influenzae

Klebsiella
species
Neisseria gonorrhoeae1

Neisseria meningitidis1

Shigella
species

Other Microorganisms

Actinomyces species
Borrelia recurrentis

Chlamydophila psittaci

Chlamydia trachomatis

Clostridium
species
Entamoeba
species
Fusobacterium nucleatum
subspecies fusiforme
Mycobacterium marinum

Mycoplasma pneumoniae

Propionibacterium acnes

Rickettsiae

Treponema pallidum
subspecies pallidum
Treponema pallidum
subspecies pertenue
Ureaplasma urealyticum

Susceptibility Test Methods

When available, the clinical microbiology laboratory should provide the results of in vitro susceptibility test results for antimicrobial drugs used in resident hospitals 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 an antibacterial drug for treatment.

Dilution Techniques

Quantitative methods are used to determine antimicrobial minimal inhibitory concentrations (MICs). These MICs provide estimates of the susceptibility of bacteria to antimicrobial compounds. The MICs should be determined using a standardized method (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of tetracycline (class) or minocycline powder.1,2 The MIC values should be interpreted according to the criteria provided in Table 1.

Diffusion Techniques

Quantitative methods that require measurement of zone diameters also provide reproducible estimates of the susceptibility of bacteria to antimicrobial compounds. The zone size provides an estimate of the susceptibility of bacteria to antimicrobial compounds. The zone size should be determined using a standardized method.2,3 This procedure uses paper disks impregnated with 30 μg tetracycline (class disk) or 30 μg minocycline to test the susceptibility of microorganisms to minocycline. The disk diffusion interpretive criteria are provided in Table 1.

Table 1: Susceptibility Test Interpretive Criteria for Minocycline and Tetracycline

Species Minimal Inhibitory Concentration (mcg/mL) Zone Diameter (mm) Agar Dilution (mcg/mL)
S I R S I R S I R
Enterobacteriaceaea
  Minocycline ≤ 4 8 ≥ 16 ≥ 16 13 - 15 ≤ 12 _ _ _
  Tetracycline ≤ 4 8 ≥ 16 ≥ 15 12 -14 ≤ 11 -- -- --
Acinetobactera
  Minocycline ≤ 4 8 ≥ 16 ≥ 16 13 - 15 ≤ 12 _ _ _
  Tetracycline ≤ 4 8 ≥ 16 ≥ 15 12 -14 ≤ 11 -- -- --
Haemophilus influenzae
  Tetracycline ≤ 2 4 ≥ 8 ≥ 29 8 2 1 2 ≤ 25
Streptococcus pneumoniae
  Tetracycline ≤ 1 2 ≥ 4 ≥ 28 25 -27 ≤ 24
Staphylococcus aureusa
  Minocycline ≤ 4 8 ≥ 16 ≥ 19 15 - 18 ≤ 14 _ _ _
  Tetracycline ≤ 4 8 ≥ 16 ≥ 19 15 - 18 ≤ 14 -- -- --
Vibrio choleraea
  Minocycline ≤ 4 8 ≥ 16 ≥ 16 13 - 15 ≤ 12
  Tetracycline ≤ 4 8 ≥ 16 ≥ 19 15 - 18 ≤ 14 -- -- --
Neisseria meningitidis b
  Minocycline - - - ≥ 26 - - ≤ 2 - -
Bacillus anthracisb
  Tetracycline ≤ 1 - - - - - - - -
Francisella tularensisb
  Tetracycline ≤ 4 - - - - - - - -
Yersinia pestis
  Tetracycline ≤ 4 8 ≥ 16 _ _ _ _ _ _
a Organisms that are susceptible to tetracycline are also considered susceptible to minocycline. However, some organisms that are intermediate or resistant to tetracycline may be susceptible to minocycline.
bThe current absence of resistance isolates precludes defining any result other than “susceptible”. If isolates yielding MIC results other than susceptible, they should be submitted to a reference laboratory for further testing.

A report of “Susceptible” indicates that the antimicrobial drug is likely to inhibit growth of the microorganism if the antimicrobial compound reaches the concentrations usually achievable at the site of infection. 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 antimicrobial drug is not likely to inhibit the growth of the microorganism if the antimicrobial compound reaches the concentrations usually achievable at the site of infection; other therapy should be selected.

Quality Control

Standardized susceptibility test procedures require the use of laboratory controls to monitor and ensure the accuracy and precision of supplies and reagents used in the assay, and the techniques of the individuals performing the test1,2,3. Standard tetracycline (class compound) or minocycline powder should provide the following range of MIC values noted in Table 2. For the disc diffusion technique, using the 30 mcg tetracycline or 30 mcg minocycline disk the criteria in Table 2 should be achieved.

Table 2: Acceptable Quality Control Ranges for Minocycline and Tetracycline

Species Minimal Inhibitory Concentration (mcg/mL) Zone Diameter (mm) Agar Dilution (mcg/mL)
Enterococcus faecalis ATCC 29212
  Minocycline 1 - 4 -- --
  Tetracycline 8 - 32 -- --
Escherichia coli ATCC 25922
  Minocycline 0.25 - 1 19 -25 --
  Tetracycline 0.5 - 2 18 -25 --
Haemophilus influenzae ATCC 49247
  Tetracycline 4 -32 14 -22 --
Neisseria gonorrhoeae ATCC 49226
  Tetracycline -- 30 -42 0.25 - 1
Staphylococcus aureus ATCC 25923
  Minocycline 25 - 30 --
  Tetracycline 24 -30 --
Staphylococcus aureus ATCC 29213
  Minocycline 0.06 - 0.5 --
  Tetracycline 0.12 - 1 --
Streptococcus pneumoniae ATCC 49619
  Tetracycline 0.06 - 0.5 27 -31 --

Animal Pharmacology And Toxicology

Minocycline HCl has been observed to cause a dark discoloration of the thyroid in experimental animals (rats, minipigs, dogs, and monkeys). In the rat, chronic treatment with minocycline hydrochloride has resulted in goiter accompanied by elevated radioactive iodine uptake and evidence of thyroid tumor production. Minocycline hydrochloride has also been found to produce thyroid hyperplasia in rats and dogs.

REFERENCES

1. Clinical and Laboratory Standards Institute. Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria that Grow Aerobically; Approved Standard-Ninth Edition; Document M07-A9, Vol. 32, No. 2, January, 2012. Clinical and Laboratory Standards, 940 West Valley Rd., Suite 2500, Wayne, PA 19087-1898.

2. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Disk Susceptibility Tests; Approved Standard-Eleventh Edition; Document M02-A11, Vol. 32, No. 1, January, 2012 . Clinical and Laboratory Standards, 940 West Valley Rd., Suite 2500, Wayne, PA 19087-1898.

3. Clinical and Laboratory Standards Institute. Performance Standards for Antimicrobial Susceptibility Testing; Twenty-Fourth Informational Supplement. Document M100-S24, Vol. 32, No. 3, January, 2014. Clinical and Laboratory Standards, 940 West Valley Rd., Suite 2500, Wayne, PA 19087-1898.

Last reviewed on RxList: 4/14/2015
This monograph has been modified to include the generic and brand name in many instances.

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