(M1030-05-29) Preparation and Characterization of Pregabalin Loaded Liposomes for Topical Drug Delivery: Utilizing the Novel Platform Technology for the Effective Treatment of Neuropathic Pain Management

Purpose: Neuropathic pain (NP) is defined as a painful condition caused by neurological lesions or diseases, prevalent and challenging to treat. For NP, Pregabalin (PG) is the most prescribed drug by physicians currently available in oral dosage forms like tablets, capsules, and oral solutions. In the previous study, we successfully designed, developed, and evaluated a novel extended-release liposomal topical cream of Pregabalin [1]. While our formulation provided excellent release and dermal distribution, we still need to be more precise about the characterization such as liposome Lamellarity, Lipid content, Size analysis, Stability, Encapsulation efficiency, Visualization, Zeta potential, Liposome internal environment, and Release kinetics. Characterizing the liposome was challenging with the previously prepared liposomal cream formulation as it had a complex microstructure forming bases in the formulation. Hence in our current study, a core liposomal solution was developed with controlled process parameters for better characterization of liposomes. The prepared core liposomes can be incorporated in suitable dosage forms like gel, cream, transdermal patches, and topical solutions. In the current study, our strategy is to prepare core liposomes using the ethanol injection method for better characterization and formulate a topical solution by employing the core liposomes where PG will be loaded in both the lipid and aqueous phases of liposomes. We hypothesize that PG in the lipid phase serves as an extended-release and PG in the aqueous phase serves as an immediate release to enhance the bioavailability with mitigated side effects for NP therapy.

Methods: The Core PG liposomes were prepared by using the ethanol injection method. This technique entails injecting a phospholipid solution of ethanol into a stirred aqueous solution. The ethanol's diffusion causes the dissolved phospholipids to precipitate to form bilayer phospholipid fragments, which fuse to form closed liposomal structures [2]. The raw materials were selected in such a way as to prepare the liposome bilayers, to increase the solubility of the PG in the liposomal bilayers as well as penetration into the skin. PG is a BCS class 1 drug, and the solubility studies proved that PG is soluble in a phospholipid solution of ethanol. L-α-phosphatidylcholine (95%) (Soy) was used as a phospholipid and cholesterol was used as stabilizing agent for the lipids. Other excipients like Tween 80 as an emulsifier, Isopropyl myristate (IPM) as an emollient, Transcutol HP as a solvent, benzyl alcohol as a preservative, Propylene glycol, Glycerine as humectant were selected (Table-1). The lab batches were prepared with the ethanol injection method (Figure-1). During the process, Phospholipid (7%w/w) was added to ethanol (15% w/w), heated to 55°C under mixing at 700 RPM followed by the addition of cholesterol (0.5% w/w) and PG (0.5% w/w) until dissolved. In another phase, PG (1.5% w/w) was added to the purified water-46.5% w/w (55°C), and mixed until dissolved. The prepared lipid solution (Phospholipid + cholesterol + PG + ethanol) was added to the aqueous phase through a syringe in a controlled manner at 900 RPM at 55°C. The resultant solution with core liposomes was pre-homogenized with Silverson^® L5M-A homogenizer at 3000 RPM and passed through a homogenization using Microfluidics^™ M110P high-pressure Microfluidizer^® at 25000 psi pressure at room temperature. The obtained core liposomes were added to the solution containing Propylene glycol-7%, Glycerine-5%, Tween80-1.5%, Transcutol HP-10%, IPM-5%, Benzyl alcohol-0.5% (%w/w) and mixed at 900RPM. Samples were evaluated for the structure of liposomes in core liposomes and final dosage form.

Results: The PG-liposomal topical solution was successfully manufactured by following the ethanol injection method for preparing core liposomes loaded with PG. The microscopy analysis was done using a Nikon Eclipse microscope to observe the structure of liposomes. In Figure 2, the appearance of a round spherical structure in core liposomes and liposomal topical solution confirmed the formation of liposomes. The pH of the finished topical solution formulation was found to be between 4.0 to 5.0. The prepared topical solution was stable at 2-8°C storage condition for 1 month without any phase separation.

Conclusion: The topical dosage form of PG is not available in the market for the treatment of NP.  An effort has been made to develop a PG topical liposomal formulation that is more effective in treating NP by improving its efficacy and bioavailability. Our current approach has enabled us to develop the liposomal topical solution containing core liposomes prepared by the ethanol injection method. This research forms the basis for preparing other liposomal topical dosage forms such as gels, creams, and ointments by following the core liposomal technique.

References: [1] Chetan Chure, AAPS ePoster Library. Chure C. 10/23/2023; 393311; M0930-08-50
[2] Du G, Sun X. Ethanol Injection Method for Liposome Preparation. Methods Mol Biol. 2023;2622:65-70. doi: 10.1007/978-1-0716-2954-3_5. PMID: 36781750


Figure 1.Core liposome preparation by ethanol injection method


Figure 2.Liposomal microscopy analysis


Table 1: Liposomal formulation composition