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 by binding to the 30S ribosomal subunit. Tetracycline is active against a broad 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.

Tetracycline has been shown to be active against most isolates of the following bacteria, both in vitro and in clinical infections as described in theINDICATIONS AND USAGE section of the package insert.

Gram-negative Bacteria

Acinetobacter species
Bartonella bacilliformis
Brucella species
Campylobacter fetus
Enterobacter aerogenes
Escherichia coli
Francisella tularensis
Haemophilus ducreyi
Haemophilus influenzae
Klebsiella species
Klebsiella granulomatis
Neisseria gonorrhoeae
Shigella species
Vibrio cholerae
Yersinia pestis

Gram-positive Bacteria

Bacillus anthracis
Streptococcus pyogenes
Streptococcus pneumoniae
Staphylococcus aureus
Listeria monocytogenes

Anaerobes

Bacteroides species
Clostridium species
Fusobacterium fusiforme
Propionibacterium acnes

Other Bacteria

Actinomyces species
Borrelia recurrentis
Chlamydophila psittaci
Chlamydia trachomatis
Rickettsiae
Treponema pallidum
Treponema pallidum subspecies pertenue

Parasites

Entamoeba species
Balantidium coli

Susceptibility Testing

For specific information regarding susceptibility test interpretive criteria and associated test methods and quality control standards recognized by FDA for this drug, please see: https://www.fda.gov/STIC

DOSAGE AND ADMINISTRATION

Adults: Usual daily dose, 1 gram as 500 mg twice a day or 250 mg four times a day. Higher doses such as 500 mg four times a day may be required for severe infections or for those infections which do not respond to the smaller doses.

For pediatric patients above eight years of age: Usual daily dose, 10 mg/lb to 20 mg/lb (25 mg/kg to 50 mg/kg) body weight divided in four equal doses.

Administration of adequate amounts of fluid with the capsule formulation of tetracycline is recommended to wash down the drug and reduce the risk of esophageal irritation and ulceration (seeADVERSE REACTIONS).

Absorption of tetracycline is impaired by antacids containing aluminum, calcium or magnesium and preparations containing iron, zinc or sodium bicarbonate. Food and some dairy products also interfere with absorption.

When used in streptococcal infections, therapy should be continued for 10 days.

For treatment of brucellosis, 500 mg tetracycline four times a day for three weeks accompanied by streptomycin, 1 gram intramuscularly twice daily the first week and once daily the second week.

For the treatment of syphilis in patients allergic to penicillin, the following dosage of tetracycline is recommended: early syphilis (less than one year’s duration), 500 mg four times a day for 15 days. Syphilis of more than one year’s duration (except neurosyphilis), 500 mg four times a day for 30 days.

For treatment of gonorrhea, the recommended dose is 500 mg by mouth four times a day for seven days.

Uncomplicated urethral, endocervical or rectal infections in adults caused by Chlamydia trachomatis: 500 mg, by mouth, four times a day for at least seven days.

In cases of moderate to severe acne which, in the judgement of the clinician, require long-term treatment, the recommended initial dosage is 1 gram daily in divided doses. When improvement is noted, reduce dosage gradually to maintenance levels ranging from 125 mg to 500 mg daily. In some patients it may be possible to maintain adequate remission of lesions with alternate day or intermittent therapy. Tetracycline therapy of acne should augment the other standard measures known to be of value. Duration of long-term treatment which can safely be recommended has not been established (seeWARNINGS and Carcinogenesis, Mutagenesis, Impairment of Fertility).

Use in Specific Population

In patients with renal impairment (seeWARNINGS): decrease total dosage by reduction of recommended individual doses and/or by extending time intervals between doses.