Combined effect of liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate in rat skin.

In this report, we investigated the combined effect of drug liposomalization and addition of glycerol on the transdermal delivery of isosorbide 5-nitrate (ISN) in rat abdominal skin in vitro. Occlusive application of both liposomal and aqueous ISN solution, with and without addition of 5% glycerol, showed that drug liposomalization and addition of glycerol has far-reaching implications for ISN permeation and accumulation in 4 and 8 weeks old rat abdominal skin. Using 8 weeks old rat abdominal skin, the optimal concentration of glycerol to be added to liposomal ISN was found to be 5%. The ISN mean values permeated through and accumulated in stripped 8 weeks old rat abdominal skin from those formulations described above were not significant different, which might indicate the combined effect of glycerol and liposomal ISN resides solely in the stratum corneum (SC). Based on previous reports, the enhancement effect of glycerol might be due to an increase in the SC hydration, and perhaps due to subtle changes in the lipid organization caused by penetration of liposomal lipids within the SC intercellular spaces. These data might provide evidence that glycerol action on SC is useful to facilitate skin permeation and accumulation of drugs formulated in liposome.

Clinical trials for drug approval: a pilot study of the view of doctors at Tokushima University Hospital.

The development of new and useful pharmaceutical drugs is essential in order to improve the quality of drug therapeutics. Clinical trials play a central role in drug development. Over time, the clinical trial infrastructure has improved and is now integrating the contribution of clinical research coordinators (CRC). Nevertheless, the attitude of doctors towards clinical trials still favors conventional/historical methodologies. In the present study, we explored the view of doctors towards clinical trials for drug development, in order to improve communication among participants, sponsors, and investigators.A questionnaire was designed for this pilot study. The questionnaire included general attitudes, difficult points, the benefit of doctors in participating as investigators, special attention requirements, and the expected role of CRC in clinical trials for drug approval. In addition, the appropriate use of the outpatient clinic was examined. The questionnaire was provided to doctors in each department of Tokushima University Hospital in 2000 and 2004. Because of the small number of subjects included in this pilot study, no statistical analysis is presented. A total of 89 (81%) and 62 (56%) doctors among 110 responded to the survey in 2000 and 2004, respectively. Inquiries about the familiarity of the physicians with clinical trials for drug approval revealed that 84% in 2000 and 66% in 2004 were aware of such trials. The attitude towards participating as investigators in the clinical trials was favorable, with a response of 66% in 2000 and 58% in 2004. Patients' refusal and the informed consent process were considered difficult areas by many doctors. Expected roles of CRC included activities based on the nurse's specialty. Although many doctors agreed to take care of the study participants separately from the clinical practice, they lacked the time to do so. In spite of the doctors' workload reduction by introduction of the CRC concept, their views regarding clinical trials for drug approval remain conventional. Further refinement in the support process by CRC should be considered in our hospital, and the views of the doctors should be investigated in a larger study, in order to promote clinical trials for drug approval in Japan.

Inducing effect of liposomalization on the transdermal delivery of hydrocortisone: creation of a drug supersaturated state.

In order to investigate the effect of liposomal drugs on skin delivery, it was postulated that the process of liposomalization might lead the drug to an overpredicted solubility state which has far-reaching implications for drug skin permeation and accumulation. In this regard, conventional (CL) and flexible liposomes (FL) were prepared by the lipid film hydration method and the particles were downsized by sonication using hydrocortisone (HC) as a poorly water soluble model drug. The solutions derived from the whole CL and FL suspensions eluted on a Sephadex G-50 column (SG-50) demonstrated that most part of HC not only resides solely in the water phase but also it might exist in an improved solubility state. The results of the in vitro study using rat abdominal skin and occlusive application indicated that HC penetrated and accumulated much better solely than when associated with CL or FL. In regard to the penetration of the non-entrapped HC associated to liposomes bilayer fragments, a very small amount of phospholipids in the non-liposomal part eluted on SG-50 was found that could not justify by itself the penetration of HC associated to liposome bilayer fragments. It was proposed that all the steps of the liposomes preparation process might contribute for the increased HC solubility state, but definitively the presence of phospholipids played a crucial role on improving the HC solubility in the absence of sodium cholate. In comparison with commercially available ointments, the non-entrapped HC solution derived from the whole CL suspension eluted on SG-50 showed a higher concentration of HC accumulated and more uniformly distributed as well in the epidermis and dermis compartments. In addition, the thermodynamic activity of the non-entrapped HC solutions maintaining a driving force of the drug across the skin barrier pointed out that the level of HC solubility achieved during liposome preparation has far-reaching implication for drug skin permeation and accumulation in the experimental conditions used. The findings also indicated that the non-entrapped drug solutions obtained on the process of liposomalization could be useful on transdermal drug delivery systems, particularly for improving the permeation and accumulation capacity of poorly soluble drugs.