Antibacterial (systemic, topical); antiprotozoal - Tetracyclines are broad - spectrum bacteriostatic agents and act by inhibiting protein synthesis by blocking the binding of aminoacyl tRNA(transfer RNA) to the mRNA(messenger RNA) ribosome complex.
Antiacne agent (topical) - probably due to their antibacterial activity. Topical tetracyclines are thought to suppress the growth of propionibacterium acnes, an anaerobe found in sebaceous glands and follicles. P. acnes produces proteases hyaluronidases, lipases, and chemotactic factors, alI of which can produce inflammatory components or inflammation directly.

Systemic tetracyclines are indicated in the treatment of:
Acne vulgaris - actinomycosis - anthrax - bronchitis - brucellosis (concurrently with streptomycin) - conjunctivitis, inclusion genitourinary tract infections - gingivostomatitis, necrotizing ulcerative - lymphogranuloma venereum - otitis media - pharyngitis, bacterial - pneumonia and sinusitis - psittacosis - Q fever - rickettsial pox - rocky mountain spotted fever - typhus infections - relapsing fever - skin and soft tissue infections - syphilis - trachoma - urinary tract infections, bacterial - amebiasis, extraintestinal - malaria - yaws.
Topical tetracyclines are indicated in the treatment of:
Ance vulgaris - Skin infections and dermal ulcer.

Cross - sensitivity and / or related problems: patients hypersensitive to one tetracycline may be hypersensitive to other tetracyclines also.
Use of systemic tetracyclines during pregnancy or in infant and children up to 8 years of age, may cause permanent discoloration of teeth, enamel hypoplasia.

Tetracyclines cross the placenta. They should not be used during the last half of pregnancy.
Tetracyclines are distributed into breast milk and use is not recommended during breast - feeding.

Combinations containing any of the following medications, depending on the amount present, may interact with this medication:
Antacids, calcium supplements such as calcium carbonate, choline and magnesium salicylates, iron supplements, magnesium containing laxatives, sodium bicarbonate, cholestyramine, cloestipol, contraceptives (estrogen containing).
Tetracyclines may interfere with the bactericidal effect of penicillins in the treatment of meningitis or when a rapid bactericidal effect is necessary, it is best to avoid concurrent therapy.
Topical tetracyclines may interact with these medications:
Abrasive or medicated soaps or cleansers - Acne preparations, topical - Alcohol containing preparations, topical such as after - shave lotions - Cosmetics - Isotretinoin - peeling agents.

Those indicating need for medical attention; Incidence more frequent:
Discoloration of infant's or children's teeth, photosensitivity.
Incidence rare: Benign intracranial hypertension, hepatotoxicity, pancreatitis.
Topical tetracyclines; Those indicating need for medical attention: pain, redness, swelling, or other sign of irritation not present before therapy.

Capsules, usual adults and adolescent dose: Antibacterial (systemic); Antiprotozoal - Oral, 250 to 500 mg every 6 hours; or 500 mg to 1 gram every 12 hours.
Antiacne agent (systemic) - Oral, 500 mg to 2 grams daily in divided doses initially in moderate to severe cases as adjunctive therapy.
When improvement is noted (usually after 3 weeks), dosage should be reduced gradually to a maintenance dose of 125 to 1000 mg daily.
Gonorrhea - Oral, 500 mg every 6 hours for 5 days.
Syphilis - Oral, 500 mg every 6 hours for 15 days (early syphilis) or for 1 month (late syphilis).
Usual adult prescribing limits: Up to 4 grams daily.
Usual pediatric dose - Children 8 years of age and over:
Oral, 6.25 - 12.5 mg per kg of body weight every 6 hours; 12.5 - 25 mg per kg every 12 hours.
Topical ointment: To the skin, one or two times a day.