CLINICAL PHARMACOLOGY
Corticosteroids suppress the inflammatory response to a variety of agents and they probably delay or slow healing. Since corticoids may inhibit the body's defense mechanism against infection, a concomitant antimicrobial drug may be used when this inhibition is considered to be clinically significant in a particular case.
The anti-infective component in the combination is included to provide action against specific organisms susceptible to it.
Terramycin is considered active against the following microorganisms:
- Rickettsiae (Rocky Mountain spotted fever, typhus fever and the typhus group, Q fever, rickettsialpox and tick fevers),
- Mycoplasma pneumoniae (PPLO, Eaton Agent),
- Agents of psittacosis and ornithosis,
- Agents of lymphogranuloma venereum and granuloma inguinale,
- The spirochetal agent of relapsing fever (Borrelia recurrentis).
The following gram-negative microorganisms:
- Haemophilus ducreyi (chancroid),
- Pasteurella pestis and Pasteurella tularensis,
- Bartonella bacilliformis,
- Bacteroides species,
- Vibrio comma and Vibrio fetus,
- Brucella species (in conjunction with streptomycin).
Because many strains of the following groups of microorganisms have been shown to be resistant to tetracyclines, culture and susceptibility testing are recommended.
Oxytetracycline is indicated for treatment of infections caused by the following gram-negative microorganisms, when bacteriologic testing indicates appropriate susceptibility to the drug:
- Escherichia coli,
- Enterobacter aerogenes (formerly Aerobacter aerogenes),
- Shigella species,
- Mima species and Herellea species,
- Haemophilus influenzae (respiratory infections),
- Klebsiella species (respiratory and urinary infections).
Oxytetracycline is indicated for treatment of infections caused by the following gram-positive microorganisms when bacteriologic testing indicates appropriate susceptibility to the drug:
Streptococcus species:
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 organism has been demonstrated to be sensitive.
For upper respiratory infections due to Group A beta-hemolytic streptococci, pencillin is the usual drug of choice, including prophylaxis of rheumatic fever.
Diplococcus pneumoniae,
Staphylococcus aureus, skin and soft tissue infections. Oxytetracycline is not the drug of choice in the treatment of any type of staphylococcal infections.
When penicillin is contraindicated, tetracyclines are alternative drugs in the treatment of infections due to:
- Neisseria gonorrhoeae,
- Treponema pallidum and Treponema pertenue (syphilis and yaws),
- Listeria monocytogenes,
- Clostridium species,
- Bacillus anthracis,
- Fusobacterium fusiforme (Vincent's infection),
- Actinomyces species.
Tetracyclines are indicated in the treatment of trachoma, although the infectious agent is not always eliminated, as judged by immunofluorescence.
Inclusion conjunctivitis may be treated with oral tetracyclines or with a combination of oral and topical agents.
When a decision to administer both a corticoid and an antimicrobial is made, the administration of such drugs in combination has the advantage of greater patient compliance and convenience, with the added assurance that the appropriate dosage of both drugs is administered, plus assured compatibility of ingredients when both types of drug are in the same formulation and, particularly, that the correct volume of drug is delivered and retained.
The relative potency of corticosteroids depends on the molecular structure, concentration, and release from the vehicle.
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