Chloramphenicol and Tetracyclines

Chloramphenicol

• It was first obtained by Streptomyces venezuelae in 1947.
• It has nitrobenzene substitution which is responsible for antibacterial activity.

Chloramphenicol

• Chemistry
• Hydroxyl groups are present at position 1 and 3
• Dichloroacetamido group is present at position 2.
• It has two chiral centers C2 and C3.

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• Physical properties
• It is available as Chloramphenicol, Chloramphenicol palmitate or Chloramphenicol sodium succinate.
• Chloramphenicol exists in white to greyish white or yellowish white, fine crystalline powder, needles or elongated plates.
• It is odorless
• It has bitter taste. So chloramphenicol palmitate is often used to mask bitter taste which is a tasteless product.
• Chloramphenicol is slightly soluble in water and in ethanol.
• Chloramphenicol palmitate is practically insoluble in water and is slightly soluble in ethanol.
• It is sensitive to light, moisture, pH and temperature.
• Its melting point is 149-153ºC.

• Stability and Storage
• It is stable in bulk but unstable in solution form. Its stability depends upon moisture, light and heat.
• So it should be stored in a tightly closed container in a cool and dry place.
• Uses
• Typhoid fever
• Bacterial meningitis
• Rickettsial infection
• Eye and ear infection
• Brucellosis
• Anaerobic infections
• (limited used due to reisistance)

Brucellosis is a zoonotic infection caused by the bacterial genus Brucella

Rickettsiae comprise a group of microorganisms that phylogenetically occupy a position between bacteria and viruses.

Tetracyclines

• Tetracyclines were discovered by Benzamin Minge Duggar in 1945.
• Tetracyclines are group of broad spectrum antibiotic having common basic structure as:

General chemistry

• Tetracyclines have four homocyclic rings.
• They are the derivatives of octahydronaphthacene.
• They consist of polyketone and polyhydroxy functional groups.
• Tetracyclines can act as a ligand to form complex with bivalent metal ions and forms pharmacologically inert complex.
• (Therefore it should not be administered with milk)

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Classification

• Short acting: Tetracycline, Chlortetracycline
• Intermediate acting: Demeclocycline, Methacycline
• Long acting: Doxycycline, Minocycline

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Tetracycline

• Chemistry
• It consists of amide group at position 2.
• Hydroxyl groups are present at C3, C6, C10 and C12
• Ketone groups are present at C1 and C11.
• Dimethyl amino group is present at position 4.
• It consists of five double bonds.

• Physical properties
• It is available as Tetracycline, Tetracycline Hydrochloride.
• It is yellow colored, crystalline powder.
• It is sensitive to light (darkens on exposure to sun)
• Tetracycline is very slightly soluble in water and slightly soluble in ethanol.
• Tetracycline Hydrochloride is freely soluble in water and slightly soluble in ethanol.
• Its melting point is 170-173 ºC.

• Stability and Storage
• It is photosensitive compound which darkens on exposure to sunlight.
• So it should be stored in tightly closed, light resistant container.

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• Uses
• Syphilis
• Cholera
• Gonorrhea
• Chlamydial infection
• Urinary Tract Infection
• Amoebic dysentery
• Plague
• Other susceptible gram positive and negative infections.

Plague is a serious illness caused by a germ called Yersinia pestis

Chlamydial infection is caused by a bacterium called Chlamydia trachomatis

Cholera is caused by bacteria Vibrio cholerae

Gonorrhea is a sexually transmitted disease (STD) caused by infection with the Neisseria gonorrhoeae bacterium

Doxycycline

• Chemistry
• It is the derivative of tetracene.
• Carboxamide group is present in C2.
• Dimethyl amino group is present at C4.
• Hydroxyl groups are present at C3, C5 and C11.
• It consists of five double bonds.
• Doxycycline is a amphoteric compound as it can act as both acid and base.

• Physical properties
• It is available as Doxycycline Hydrochloride.
• Doxycycline Hydrochloride is freely soluble in water and sparingly soluble in ethanol.
• Doxycycline is slightly soluble in water, sparingly soluble in alcohol.
• It is yellow colored crystalline powder.
• It possess slightly ethanolic odor.
• It is sensitive to light.
• It is also sensitive to moisture and high temperature.
• Its melting point is 201 ºC.

• Stability and Storage
• It is sensitive to light, moisture and high temperature. So it should be stored in tightly closed light resistant container protected from extremes of temperature at the temperature no exceeding 30°C.

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• Uses
• Brucellosis
• Cholera
• Syphilis
• Uncomplicated Gonorrhea
• Chlamydia
• Prophylaxis of malaria
• Purulent cellulitis
• Rosacea
• Other gram positive and gram negative infections