Effect of temperature on bleeding and drug release from a liquid droplet dispersion ointment

A liquid droplet dispersion ointment, LDDS, a formulation containing a drug solution as droplets in an oily vehicle, is excellent for percutaneous drug absorption. Bleeding of LDDS and in vitro drug release from LDDS were found to be enhanced by temperature increase. The influence of temperature on the physical properties of LDDS was studied using differential scanning calorimetry and X-ray diffraction spectroscopy. The liquid component content, possibly a hydrocarbon in the vehicle, increased with temperature; this may have been due to melting of the vehicle. In this liquid component, the drug concentration measured by HPLC increased with temperature. This change in the drug concentration may cause an increase in drug release, leading to the conclusion that, compared with conventional ointments, temperature has much greater effect on drug release from LDDS.