Following a single dose of 200 mg administered intravenously to 10 healthy male volunteers, serum levels ranged from 2.52 to 6.63 µg/mL (average 4.18), after 12 hours they ranged from 0.82 to 2.64 µg/mL (average 1.38). In a group of 5 healthy male volunteers, levels of 1.4 to 1.8 g/mL were maintained at 12 and 24 hours with doses of 100 mg every 12 hours for three days. When given 200 mg once daily for three days, the serum levels had fallen to approximately 1 g/mL at 24 hours. The serum half-life following I.V. doses of 100 mg every 12 hours or 200 mg once daily did not differ significantly and ranged from 15 to 23 hours. The serum half-life following a single 200 mg oral dose in 12 essentially normal volunteers ranged from 11 to 17 hours, in 7 patients with hepatic dysfunction it ranged from 11 to 16 hours, and in 5 patients with renal dysfunction from 18 to 69 hours.

Intravenously administered minocycline appears similar to oral doses in excretion. The urinary and fecal recovery of oral minocycline when administered to 12 normal volunteers was 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 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.

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 anthracis¹
Listeria monocytogenes¹
Staphylococcus aureus
Streptococcus pneumoniae

Aerobic Gram-Negative Microorganisms

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 gonorrhoeae¹
Neisseria meningitidis¹
Shigella species

“Other” Microorganisms

Actinomyces species¹
Borrelia recurrentis
Chlamydia psittaci
Chlamydia trachomatis
Clostridium species¹
Entamoeba species
Fusobacterium nucleatum subspecies fusiforme¹
Mycobacterium marinum
Mycoplasma pneumoniae
Propionibacterium acnes
Rickettsiae
Treponema pallidum subspecies pallidum¹
Treponema pallidum subspecies pertenue¹
Ureaplasma urealyticum

Susceptibility Tests

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

Dilution techniques

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