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Category Antibacterial; antirickettsial.

          Chloramphenicol contains not less than 97.0 per cent and not more than 103.0 per cent of C₁₁H₁₂Cl₂N₂O₅, calculated on the dried basis.

Description Fine, white to greyish white or yellowish white, crystalline powder or crystals, needles or elongated plates.

Solubility Slightly soluble in water; freely soluble in ethanol and in propylene glycol; slightly soluble in ether.

Stability It is very stable unless being exposed to excessive light or moisture. In aqueous solutions, chloramphenicol degrades mainly by hydrolysis with the release of chloride ions. Hydrolysis is lowest at pH 6. It may also degrade by a photolytic reaction.

Warning
          1. Jarisch-Herxheimer-like reactions may occur in patients receiving chloramphenicol for the treatment of typhoid fever.
          2. It should be reserved for serious infections in which less toxic antibacterials are ineffective or contraindicated.
          3. It may depress bone marrow or may cause fatal idiosyncratic aplastic anemia. It may also interfere with the development of immunity and, thus, should not be given during active immunization.
          4. It should be used with extreme caution in premature or very young infants to avoid “grey syndrome” toxicity; in patients with impaired renal or hepatic function; or in those who are receiving oral anticoagulants, oral hypoglycemics, phenytoin, or bone marrow depressants (e.g., antineoplastics, phenylbutazone, etc.).
          5. It is not recommended in pregnancy at term, during labour or in nursing mothers.

Precaution
          1. Complete blood count should be performed prior to and approximately every 2 days during chloramphenicol therapy. Careful observation for sudden sore throat or development of additional infection are also recommended.
          2. Long-term therapy may cause headache, mental confusion, delirium, optic and/or peripheral neuritis, superinfection, or abnormal bleeding.
          3. If superinfection occurs, the drug should be discontinued and appropriate therapy instituted.

Packaging and storage Chloramphenicol shall be kept in tightly closed containers, protected from light.

Labelling The label on the container states (1) storage condition; (2) sterile or non-sterile grade.

Identification
          A. The infrared absorption spectrum is concordant with the spectrum obtained from Chloramphenicol RS (Appendix 2.1) or with the reference spectrum of Chloramphenicol.
          B. The retention time of the major peak in the chromatogram of the Assay preparation corresponds to that in the chromatogram of the Standard preparation, as obtained in the Assay.

Crystallinity It is crystalline (Appendix 4.14).

Melting range 149^º to 153^º (Appendix 4.3).

pH 4.5 to 7.5, in a 2.5 per cent w/v suspension (Appendix 4.11).

Specific rotation +17^º to +20^º, determined in a 5.0 per cent w/v solution in absolute ethanol (Appendix 4.8).

Chromatographic purity Carry out the test as described in the “Thin-layer Chromatography” (Appendix
3.1), using silica gel HF254 as the coating substance and a mixture of 79 volumes of chloroform, 14 volumes of methanol and 7 volumes of glacial acetic acid as the mobile phase. Apply separately to the plate, 20 μl of each of the following solutions. For solution (A) dissolve 10 mg of the test substance in 1 ml of methanol. For solution (B) dissolve 10 mg of Chloramphenicol RS in 1 ml of methanol. For solution (C) dilute portions of solution (B) quantitatively with methanol to obtain 100 μg per ml. For solution (D) dilute portions of solution (B) quantitatively with methanol to obtain 50 μg per ml. After removal of the plate, allow it to dry and examine under ultraviolet light (254 nm). Any spot other than the principal spot obtained from solution (A) does not exceed in size or intensity the principal spot obtained from solution (C) (1 per cent), and the sum of the impurities represented by all of the spots other than the principal spot, based on a comparison of the intensities of such spots with the intensities of the principal spots obtained from solutions (C) and (D), does not exceed 2 per cent.

Assay Carry out the determination as described in the “High-pressure Liquid Chromatography” (Appendix 3.5).
          Mobile phase Prepare a suitable filtered mixture of 55 volumes of water, 45 volumes of methanol and 0.1 volume of glacial acetic acid. Make adjustments if necessary.
          Standard preparation Dissolve an accurately weighed quantity of Chloramphenicol RS in Mobile phase and dilute quantitatively, and stepwise if necessary, with Mobile phase to obtain a solution having a known concentration of about 80 μg per ml.
          Assay preparation Transfer about 200 mg of Chloramphenicol, accurately weighed, to a 100-ml volumetric flask, add Mobile phase to volume, and mix. Transfer 4.0 ml of the resulting solution to a 100-ml volumetric flask, dilute with Mobile phase to volume, and mix.
          Chromatographic system The chromatographic procedure may be carried out using (a) a stainless steel column (10 cm × 4.6 mm) packed with octadecylsilane chemically bonded to porous silica or ceramic microparticles (5 μm), (b) Mobile phase at a flow rate of about 1 ml per minute, and (c) an ultraviolet photometer set at 280 nm.
          To determine the suitability of the chromatographic system, chromatograph Standard preparation and record the peak responses as directed under Procedure: the symmetry factor is not more than 2.0, and the relative standard deviation for replicate injections is not more than 1.0 per cent.
          Procedure Separately inject equal volumes (about 10 μl) of Standard preparation and Assay preparation into the chromatograph, record the chromatograms, and measure the responses for the major peaks.
          Calculation Calculate the content of C₁₁H₁₂Cl₂N₂O₅ in the Chloramphenicol taken, using the declared content of C₁₁H₁₂Cl₂N₂O₅ in Chloramphenicol RS.