Formulation of polyethylene glycol ointment bases suitable for tropical and subtropical climates. I

The present study dealt with the investigation of the physical characteristics of 18 polyethylene glycol ointment bases with the aim of finding out their suitability for use in tropical and subtropical climates. Different ratios of low and high molecular weight polyethylene glycols were helpful for preparation of these ointment bases. The investigated physical characteristics included the drop point, the congealing range and the spreadability properties of bases. The drop point was determined by the Ubbelohde apparatus, the congealing range by the double-walled Zhuckov flask, penetrability by penetrometer, and spreadability by the parallel plate extensometer. The results of these physical parameters indicated that PEG 400:PEG 4000 blend gave very good bases for use in tropical and subtropical areas. Furthermore, it was observed that, the type and the amount of PEG used would affect greatly the drop point, congealing range and consistency of the prepared bases. Results obtained with PEG 2000 and PEG 6000 bases showed less variability with respect to molecular weight and solid content.