Background and Importance Different formulations of topical rapamycin have been tested for facial angiofibromas in tuberous sclerosis, most using an ointment as a vehicle.

Aim and Objectives To develop a liposomal formulation and to determine the validity period according to chemical, physical and microbiological stability in rare tuberous sclerosis disease.

Material and Methods A liposomal formulation of rapamycin 0,4% was prepared in biological safety cabinet.

Packing and Conservation 20g bottle protected of ambient light and stored in a cold room at 5°C ± 3°C.

Composition rapamycin 0,4%, transcutol-P 10%, liposomal solution 25%, cholesterol 0,1%, isopropile miristrate 10%, propylene glycol 10%, carbopol 2%, NaOH 10% q.s. pH 7,5, API q.s. 20g.

1. Chemical stability: An analytical method based on liquid-liquid extraction of rapamycin with apolar solvents and analysis by high-performance liquid chromatography with ultraviolet/visible detection was developed and validated. The percentage of remaining sirolimus content (%CR) was determined by triplicate at t=0, 2, 14, 21, 28, 42, 56, 70 and 84 days.T₉₀ was established when% CR was ≤90%.

2. Physical stability: pH, uniformity, extensibility, absence of crystals and absence of phase separations were evaluated on a transparent surface according to 3 levels: level 1, the least favourable and level 3, the most favourable, at t=0 days. Further, mean particle size, zeta potential and encapsulation efficiency(EE%)was determined by triplicate at t=0 days. Mean particle size and zeta potential was determined using particle size analyser which uses laser diffraction method. EE% were determined via ultra-filtration, using Amicon^® ultra-centrifugal filters.

3. Microbiological stability: Culture samples in blood-agar media of each formulation were incubated at 37°C by duplicate at t=28,56,and 84 days.

Results Liposomal formulation were chemically, physically and microbiologically stable after 84 days. Mean particle size and zeta potential of prepared liposomes determined a good quality result of the analysis with a polydispersity index value<0.2, indicating a homogenous dispersion. EE% turned out to be very favourable for the liposomal formulation, with a high load of rapamycin per liposome formed(89%).

Conclusion and Relevance This study describes a new liposomal formulation to improve the previously treatment for facial angiofibromas in tuberous sclerosis. It also provides favourable stability data for liposomes. However, more dermokinetic and clinical studies are needed to confirm that liposomes are most appropriate to ensure effectiveness, safety and high patient satisfaction.

Conflict of Interest No conflict of interest