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The colouring matter developed in aged chloramphenicol (1) suppositories formulated with polyethylene glycol base was separated by extraction with water/n-butanol mixture, n-butanol or abs. alcohol. These extracts were tested for colour stability, the presence of the main degradation products of 1 p-nitrophenylaminopropandiol (2) and p-nitrobenzaldehyde (3), and investigated by TLC and absorption spectrum. Results showed that the extracted matter gave the tests for the main degradation products of 1. TLC of n-butanol layer of the first mixture or n-butanol extract gave 2 spots with different RF values identified as 2 and 3. In the case of abs. alcohol extract 2 spots adhering to each other were obtained. The same spots in the latter case were obtained for an equimolecular condensation product of 2 and 3 (obtained by condensation in acid medium). The absorption spectrum of the extracted matter showed high absorbance in the visible region and maxima appeared only in the UV region. The condensation product of 2 and 3 gave the same absorbance pattern and did not produce Schiff's base. The colour of the aqueous layer of the first mixture faded gradually which assured its not being due to azocompounds. These findings indicated that the discolouration may be due to complex formation. Using model systems of known chemical reactions showed that discolouration is due to complex formation between 2 and 3 between 1 and 2.

A study was conducted on the effect of certain additives on the dissolution rate of chloramphenicol. The effect of adsorbents, natural and synthetic surface active agents, diluents and lubricants was studied. Many of these additives increased the dissolution rate of chloramphenicol from capsules.

The dissolution rate of chloramphenicol from its hard gelatin capsules containing different formulations either in the form of fine powdered blend or granules was investigated. The granules were prepared by the wet method using ethanol 60%, gelatin, carboyme thyl cellulose (CMC) sodium or polyvinylpyrrolidone (PVP) as binders or by slugging at different mechanical strengths. Results showed that the more hydrophilic the formula, the more the dissolution rate of chloramphenicol. Capsules filled with fine powdered blend gave a higher dissolution of the drug than those filled with granules prepared by the wet method or granules prepared from slugs of high mechanical strengths. Of the binding agents tested in the wet method, alcohol excelled gelatin, and the latter excelled CMC sodium and PVP. Capsules filled with granules prepared from slugs of 1 kg hardness gave a dissolution rate which was either higher than or nearly approaching that of capsules filled with the corresponding fine powdered blend.

This current study was motivated, and designed in an attempt to determine the possible application of the inert, pH-insensitive, ethyl cellulose polymer as a potential sustained-release coating for oral pharmaceuticals. Coating was effected using two relatively recent techniques, namely microencapsulation by phase separation coacervation, induced by temperature change, and drug entrapment by flocculation, induced by nonsolbent addition. Chloramphenicol was used as a model drug. Results of this study revealed the fact that ethyl cellulose proved to be a potential sustained-release coating for oral dosage forms. Moreover, the effect of the coating/core ratio was exhibited both qualitatively and quantitatively. This finding could help in the design of programmed or timed-release drugs. Accordingly, this study could be considered a successful attempt towards the utlization of ethyl cellulose in of the design of sustained-release oral pharmaceuticals.

A rapid method for the determination of chloramphenicol in chloramphenicol-sulphacetamide drops is discussed. The method depends upon precipitating sulphacetamide as its silver salt by a solution of silver nitrate. Chloramphenicol is determined in the filtrate using the modified Vierordt's method. Sulphacetamide was determined by suitably diluting the drops with 0.01 N H2SO4 and then applying the modified Vierordt's method. The presence of macrogols proved not to interfere with the determination. Mean percentage recoveries +/- s.d. for chloramphenicol and sulphacetamide were found to be 100.8 +/- 0.95 and 100.2 +/- 1.0, respectively.

The stability of chlortetracycline hydrochloride at 25 and 35 degrees C in absorption base with and without antioxidant decreased during storage for 12 months, while, in water-in-oil emulsion base the medicament was more stable than in oil-in-water emulsion ointment bases. Chloramphenicol was more stable in the absorption base that contained lanolin than in the base which contained cetyl alcohol. Chloramphenicol was more stable in oil-in-water than in water-in-oil emulsion bases. The decomposition rate constant of chlortetracycline hydrochloride and chloramphenicol followed first order kinetics, when the stability study was carried out at 25 and 35 degrees C.

A mathematical model has been analyzed for the liberation process of substances (chloramphenicol) from emulsive ointments (W/O). Limitarying approximations have been derived which are useful for practical calculations. These approximations have been elaborated for the following cases: since the mass transfer resistance of diffusing substance occurs in the continuous phase, since the mass transfer resistance occurs only in the dispersed phase, then the mass transfer resistance in both phases is comparable. Experimental investigations have been carried out for the liberation process of substances from emulsive ointments. A good qualitative agreement has been found between the theoretical projections and experimental results.

1, 3 and 5% water, ethyl alcohol, glycerol and propylene glycol were incorporated into oleaginous, absorption, emulsion (O/W and W/O) and water-soluble ointment bases (resp.) containing 5% of chloramphenicol and diffusion rate via the dialysis method was measured for 2 h. The rate of release was found to be greater from water-soluble bases than from the other bases, since rates from oleaginous, absorption and W/O emulsion bases were found to be the least in this respect. The effect of liquids added to these bases on drug release was found to be less pronounced than that obtained with water-soluble and O/W emulsion bases. For O/W emulsion bases the addition of ethyl alcohol increased the release of chloramphenicol as its concentration was increased. Propylene glycol increased the release at a concentration of 3%, but higher concentration produced opposite results. Glycerol was found to have a little effect in 5% concentration, but it increased the release as the concentration dropped to 3% concentration.