(Mode of Action of Drugs)

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Chapter

1.4

Chapter

9.2 Tetracyclines, Chloramphenicol and Chemotherapy of UTI

TETRACYCLINES

The tetracyclines are a group of drugs with a
common basic chemical structure and
pharmacological activity. The first tetracycline,
chlortetracycline was isolated from
Streptomyces aureofaciens, then oxytetracycline
was derived from Streptomyces rimosus and
then tetracycline was obtained by catalytic
dehalogenation of chlortetracycline. They are
classified as in table 9.2.1.

Mechanism of Action

The tetracyclines are primarily
bacteriostatic and are thought to exert their
antimicrobial effect by the inhibition of
protein synthesis. The tetracyclines,
including doxycycline, have a similar

Tetracyclines,

Chloramphenicol

and Chemotherapy

of UTI

antimicrobial spectrum of activity against a

wide range of gram positive and negative

organisms. Cross-resistance of these

organisms to tetracyclines is common.

Antimicrobial Spectrum of Activity

Tetracyclines has one of the widest

spectrum amongst antimicrobials. The

microbes that are sensitive to tetracycline

include Staph. aureus, Staph. epidermidis,

Strep. pyogenes, Strep. viridans, Strep.

pneumoniae, Strep. faecalis (UTI), Listeria

monocytogenes, Bacillus anthracis, Clostridium

sp., Actinomyces sp., T. pallidum, T. pertenue,

Borrelia recurrentis, Fusobacterium fusiforme,

Brucella sp. and bacteroides sp. Commonly

occurring gram negative organisms e.g. H.

influenzae, H. ducreyi, Neisseria gonorrhoeae,

Table 9.2.1: Classification of tetracyclines.

Tetracycline (SUBAMYCIN) 250-500 mg/day, 1-3% topical (eye/ear drop, skin oint)

Oxytetracycline (TERRAMYCIN) 250-500 mg/day, 1-3% topical (skin, eye ointment)

Chlortetracycline (AUREOMYCIN) 250-500 mg/day, 1-3% topical (skin, eye ointment)

Demeclocycline (LEDERMYCIN) 300 mg BD, 0.5% skin oint.

Doxycycline (BIODOXI) 200 mg OD

Minocycline (CANOMYCIN) 100 mg BD