DrugLib.com — Drug Information Portal

Rx drug information, pharmaceutical research, clinical trials, news, and more

Dynacin (Minocycline Hydrochloride) - Description and Clinical Pharmacology

 
 



DYNACIN® (MINOCYCLINE HCl TABLETS, USP)

Rx Only

To reduce the development of drug-resistant bacteria and maintain the effectiveness of minocycline hydrochloride tablets and other antibacterial drugs, minocycline hydrochloride tablets should be used only to treat or prevent infections that are proven or strongly suspected to be caused by bacteria.

DESCRIPTION

Minocycline hydrochloride, a semisynthetic derivative of tetracycline, is 4,7-Bis(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,10,12,12a-tetrahydroxy-1,11-dioxo-2-naphthacenecarboxamide monohydrochloride. Its structural formula is:

                                              C23H27N3O7•HCL                                                                                  M.W. 493.94

Minocycline hydrochloride tablets for oral administration contain minocycline HCl equivalent to 50 mg, 75 mg or 100 mg of minocycline. In addition, 50 mg, 75 mg and 100 mg tablets contain the following inactive ingredients: Colloidal Silicon Dioxide, Lactose Anhydrous, Magnesium Stearate, Microcrystalline Cellulose, Povidone and Sodium Starch Glycolate. The 50 mg tablets also contain Opadry White which contains: Titanium Dioxide, Hypromellose, Polyethylene Glycol and Polysorbate 80. The 75 mg and 100 mg tablets contain Opadry Gray which contains: Titanium Dioxide, Hypromellose, Polyethylene Glycol and Iron Oxide Black.

CLINICAL PHARMACOLOGY

Minocycline hydrochloride tablets are rapidly absorbed from the gastrointestinal tract following oral administration. Following a single dose of one 100 mg tablet of minocycline hydrochloride administered to 28 normal fasting adult volunteers, maximum serum concentrations were attained in 1 to 3 hours (average 1.71 hours) and ranged from 491.71 to 1292.70 ng/mL (average 758.29 ng/mL). The serum half-life in the normal volunteers ranged from 11.38 to 24.31 hours (average 17.03 hours).

When minocycline hydrochloride tablets were given concomitantly with a meal, which included dairy products, the extent of absorption of minocycline hydrochloride tablets was slightly decreased (6%). The peak plasma concentrations were slightly decreased (12%) and delayed by 1.09 hours when administered with food, compared to dosing under fasting conditions.

In previous studies with other minocycline dosage forms, the minocycline serum half-life ranged from 11 to 16 hours in 7 patients with hepatic dysfunction, and from 18 to 69 hours in 5 patients with renal dysfunction. The urinary and fecal recovery of minocycline when administered to 12 normal volunteers is one-half to one-third that of other tetracyclines.

Microbiology

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

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:

AEROBIC GRAM-POSITIVE MICROORGANISMS

Because many strains of the following gram-positive microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are especially recommended. Tetracycline antibiotics should not be used for streptococcal diseases unless the organism has been demonstrated to be susceptible. Tetracyclines are not the drug of choice in the treatment of any type of staphylococcal infection.

  •   Bacillus anthracis
  •   Listeria monocytogenes
  •   Staphylococcus aureus
  •   Streptococcus pneumoniae

AEROBIC GRAM-NEGATIVE MICROORGANISMS

  •   Bartonella bacilliformis
  •   Brucella species
  •   Calymmatobacterium granulomatis
  •   Campylobacter fetus
  •   Francisella tularensis
  •   Haemophilus ducreyi
  •   Vibrio cholerae
  •   Yersinia pestis

Because many strains of the following groups of gram-negative microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility tests are especially recommended.

  •   Acinetobacter species
  •   Enterobacter aerogenes
  •   Escherichia coli
  •   Haemophilus influenzae
  •   Klebsiella species
  •   Neisseria gonorrhoeae
  •   Neisseria meningitidis
  •   Shigella species

"OTHER" MICROORGANISMS

  •   Actinomyces species†
  •   Borrelia recurrentis
  •   Chlamydia psittaci
  •   Chlamydia trachomatis
  •   Clostridium species†
  •   Entamoeba species
  •   Fusobacterium nucleatum ssp. fusiforme
  •   Mycobacterium   marinum
  •   Mycoplasma pneumoniae
  •   Propionibacterium acnes
  •   Rickettsiae
  •   Treponema pallidum subspecies pallidum
  •   Treponema pallidum subspecies pertenue
  •   Ureaplasma urealyticum

†When penicillin is contraindicated, tetracyclines are alternative drugs in the treatment of infections caused by the cited microorganisms.

Susceptibility Tests

Susceptibility testing should be performed with tetracycline since it predicts susceptibility to minocycline. However, certain organisms (e.g., some staphylococci, and Acinetobacter ssp.) may be more susceptible to minocycline and doxycycline than tetracycline.

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 procedure. Standardized procedures are based on a dilution method1,3 (broth or agar) or equivalent with standardized inoculum concentrations and standardized concentrations of tetracycline powder. The MIC values should be interpreted according to the following criteria:

For testing aerobic gram-negative microorganisms (Enterobacteriaceae), Acinetobacter ssp. and Staphylococcus aureus.

MIC (mcg/mL)Interpretation
≤ 4Susceptible (S)
   8Intermediate (I)
≥ 16Resistant (R)

For testing Haemophilus influenzae a and Streptococcus pneumoniae b:

MIC (mcg/mL)Interpretation
≤ 2Susceptible (S)
   4Intermediate (I)
≥ 8Resistant (R)

a. These interpretative standards are applicable only to broth microdilution susceptibility testing with Haemophilus influenzae using Haemophilus Test Medium.1

b. These interpretative standards are applicable only to broth microdilution susceptibility testing cation-adjusted Muller-Hinton broth with 2 – 5% lysed horse blood.1

For testing Neisseria gonorrhoeae c:

MIC (mcg/mL)Interpretation
≤ 0.25Susceptible (S)
       0.5– 1Intermediate (I)
≥ 2     Resistant (R)

c. These interpretative standards are applicable only to agar dilution susceptibility testing using GC agar base and 1% defined growth supplements.1

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.

Standardized susceptibility test procedures require the use of laboratory control microorganisms to control the technical aspects of the laboratory procedures. Standard tetracycline powder should provide the following MIC values:

MicroorganismMIC (mcg/mL)
Escherichia coli ATCC 259220.5–2
Enterococcus faecalis ATCC 292128–32
Staphylococcus aureus ATCC 292130.25–1
Haemophilus influenzae ATCC 492474–32
Streptococcus pneumoniae ATCC 496190.12–0.5
Neisseria gonorrhoeae ATCC 492260.25–1

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 30 mcg tetracycline (class disk) or 30 mcg minocycline to test the susceptibility of microorganisms to minocycline. Reports from the laboratory providing results of the standard single-disk susceptibility test with a 30 mcg tetracycline or minocycline disk should be interpreted according to the following criteria:

For testing aerobic gram-negative microorganisms (Enterobacteriaceae). Acinetobacter spp. and Staphylococcus aureus:

Zone Diameter (mm)Interpretation
≥ 19Susceptible (S)
15–18Intermediate (I)
≤ 14Resistant (R)

For testing Haemophilus influenzae d:

Zone Diameter (mm)Interpretation
≥ 29Susceptible (S)
26–28Intermediate (I)
≤ 25Resistant (R)

d. These zone diameter standards are applicable only to susceptibility testing with Haemophilus influenzae using Haemophilus Test Medium and a 30 mcg tetracycline disk.2

For testing Neisseria gonorrhoeae e:

Zone Diameter (mm)Interpretation
≥ 38Susceptible (S)
31–37Intermediate (I)
≤ 30Resistant (R)

e. These interpretative standards are applicable only to disk diffusion testing using GC agar and 1% growth supplements, and a 30 mcg tetracycline disk.2

For testing Streptococcus pneumoniae f:

Zone Diameter (mm)Interpretation
≥ 23Susceptible (S)
19–22Intermediate (I)
≤ 18Resistant (R)

f. These interpretative standards are applicable only to disk diffusion testing using Muller-Hinton agar adjusted with 5% sheep blood and a 30 mcg tetracycline-class disk.2

For testing Vibrio cholerae g:

Zone Diameter (mm)Interpretation
≥ 19Susceptible (S)
15–18Intermediate (I)
≤ 14Resistant (R)

g. These interpretative standards are applicable only to disk diffusion testing performed with a 30 mcg tetracycline-class disk.2

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 tetracycline.

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 30 mcg tetracycline or minocycline disk should provide the following zone diameters in these laboratory test quality control strains:

MicroorganismZone Diameter Range (mm)
TetracyclineMinocycline
Escherichia coli ATCC 2592218–2519–25
Staphylococcus aureus ATCC 2592324–3025–30
Haemophilus influenzae ATCC 4924714–22---
Neisseria gonorrhoeae ATCC 4922630–42---
Streptococcus pneumoniae ATCC 4961927–31---

ANIMAL PHARMACOLOGY AND TOXICOLOGY

Minocycline hydrochloride 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.

-- advertisement -- The American Red Cross
 
Home | About Us | Contact Us | Site usage policy | Privacy policy

All Rights reserved - Copyright DrugLib.com, 2006-2017