Effect of skin-penetrating enhancers on the thermophysical properties of cholesteryl oleyl carbonate embedded in a thermo-responsive membrane

Thermoresponsive gating membranes embedded with liquid crystal(s) for pulsatile transdermal drug delivery: An overview and perspectives

Due to the circadian rhythm regulation of almost every biological process in the human body, physiological and biochemical conditions vary considerably over the course of a 24-h period. Thus, optimal drug delivery and therapy should be effectively controlled to achieve the desired therapeutic plasma concentrations and therapeutic drug responses at the required time according to chronopharmacological concepts, rather than continuous maintenance of constant drug concentrations for an extended time period. For many drugs, it is not always necessary to constantly deliver a drug into the human body under disease conditions due to rhythmic variations. Pulsatile drug delivery systems (PDDSs) have been receiving more attention in pharmaceutical development by providing a predetermined lag period, followed by a fast or rate-controlled drug release after application. PDDSs are characterized by a programmed drug release, which may release a drug at repeatable pulses to match the biological and clinical needs of a given disease therapy. This review article focuses on thermoresponsive gating membranes embedded with liquid crystals (LCs) for transdermal drug delivery using PDDS technology. In addition, the principal rationale and the advanced approaches for the use of PDDSs, the marketed products of chronotherapeutic DDSs with pulsatile function designed by various PDDS technologies, pulsatile drug delivery designed with thermoresponsive polymers, challenges and opportunities of transdermal drug delivery, and novel approaches of LC systems for drug delivery are reviewed and discussed. A brief overview of all academic research articles concerning single LC- or binary LC-embedded thermoresponsive membranes with a switchable on-off permeation function through topical application by an external temperature control, which may modulate the dosing interval and administration time according to the therapeutic needs of the human body, is also compiled and presented. In the near future, since thermal-based approaches have become a well-accepted method to enhance transdermal delivery of different water-soluble drugs and macromolecules, a combination of the thermal-assisted approach with thermoresponsive LCs membranes will have the potential to improve PDDS applications but still poses a great challenge.

Physicochemical properties and antifungal activity of amphotericin B incorporated in cholesteryl carbonate esters

The antifungal activity of amphotericin B (AmB) incorporated in three cholesteryl carbonate esters (CCEs), sodium cholesteryl carbonate, cholesteryl palmityl carbonate, and dicholesteryl carbonate, was examined to assess their potential for use in a dry powder aerosol. Formulations containing dissolved AmB were stable for 6 months. The particle size varied inversely with liquid crystalline content with observed mass median aerodynamic diameters ranging from 4 to 8 μ m. This was consistent with the visual appearance of the liquid crystals as being low density and free flowing at room temperature. When dispersed in water, the presence of the CCE reduced the rate and extent of AmB release, consistent with the estimated liquid crystal/water partition coefficient. Nevertheless, the rate of AmB release was always sufficient to kill the fungus as established with bioactivity studies. AmB formulated with CCE as a dry powder appears to be promising for use in treating lung fungal infections.