Clinical Pharmacology:
Tetracyclines are readily absorbed and are bound to plasma protein in varying degrees. They are concentrated by the liver in the bile and excreted in the urine and feces at high concentrations in a biologically active form.
Microbiology:
Tetracyclines are primarily bacteriostatic and exert their antimicrobial effect by the inhibition of protein synthesis. Tetracycline is active against a wide range of gram-negative and gram-positive organisms. The drugs in the tetracycline class have closely similar antimicrobial spectra, and cross-resistance among them is common.
While in vitro studies have demonstrated the susceptibility of most strains of the following microorganisms, clinical efficacy for infections other than those included in the INDICATIONS AND USAGE section has not been documented.
Gram-Negative Bacteria:
Neisseria gonorrhea
Haemophilus ducrey i
Haemophilus influenzae
Yersinia pestis (formerly Pasteurella pestis)
Francisella tularensis (formerly Pasterurella tularensis)
Vibrio cholera (formerly Vibrio comma)
Bartonella bacilliformis
Brucella species
Because many strains of the following groups of gram-negative microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are recommended:
Escherichia coli
Klebsiella species
Enterobacter aerogenes
Shigella species
Acinetobacter species (formerly Mima species and Herellea species)
Bacteroides species
Gram-Positive Bacteria:
Because many strains of the following groups of gram-positive microorganisms have been shown to be resistant to tetracycline, culture and susceptibility testing are recommended. Up to 44 percent of strains of Streptococcus pyogenes and 74 percent of Streptococcus faecalis have been found to be resistant to tetracycline drugs. Therefore, tetracyclines should not be used for streptococcal disease unless the organisms have been demonstrated to be susceptible.
Streptococcus pyogenes
Streptococcus pneumoniae
Enterococcus group (Streptococcus faecalis and Streptococcus faecium)
Alpha-hemolytic Streptococci (viridans group)
Other Microorganisms:
Chlamydia psittaci
Chlamydia trachomatis
Ureaplasma urealyticum
Borrelia recurrentis
Treponema pallidum
Treponema pertenue
Clostridia species
Fusobacterium fusiforme
Actinomyces species
Bacillus anthraxis
Propionibacterium acnes
Entamoeba species
Balantidium coli
Susceptibility Testing:
A tetracycline disk may be used to determine microbial susceptibility to drugs in the tetracycline class. If the Kirby-Bauer method of disk susceptibility testing is used, a 30 mcg tetracycline disk should give a zone of at least 19 mm when tested against a tetracycline susceptible bacterial strain. Microorganisms may be considered susceptible if the MIC (minimum inhibitory concentration) is not more than 4.0 mcg/mL and intermediate if the MIC is 4.0 to 12.5 mcg/mL.
ANIMAL PHARMACOLOGY AND ANIMAL TOXICOLOGY:
Hyperpigmentation of the thyroid has been produced by members of the tetracycline class in the following species: in rats by oxytetracycline, doxycycline, tetracycline PO4 and methacycline; in minipigs by doxycycline, minocycline, tetracycline PO4 and methacycline; in dogs by doxycycline and minocycline; in monkeys by minocycline.
Minocycline, tetracycline PO4, methacycline, doxycycline, tetracycline base, oxytetracycline HCl and tetracycline HCl were goitrogenic in rats fed a low iodine diet. This goitrogenic effect was accomplished by high radioactive iodine uptake.
Administration of minocycline also produced a large goiter with high radioiodine uptake in rats fed a relatively high iodine diet.
Treatment of various animal species with this class of drugs has also resulted in the induction of thyroid hyperplasia in the following: in rats and dogs (minocycline), in chickens chlortetracycline) and in rats and mice (oxytetracycline). Adrenal gland hyperplasia has been observed in goats and rats treated with oxytetracycline.
MANUFACTURED BY
BARR LABORATORIES, INC.
POMONA, NY 10970
BR-010, 011
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