Effect of liquid additives on release of chloramphenicol from ointment bases.

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.