The use of lipids and surfactants in the pharmaceutical and nutraceutical world goes all the way back to cod liver oil and malt extract, emulsion and capsule. This was followed by the breakthrough in the late 1960s and early 1970s, where lipid-based emulsions were used for total parenteral nutrition (TPN). Since then, novel pharmaceutical formulation concepts have contributed to the introduction of a range of sophisticated lipid/surfactant-based formulations and dosage forms like: Sandimmune Neoral™ (Cyclospoin A by Novartis), Roclatrol™ (Calcitriol by Roche), Argenase™ (Amprenavir by GSK), Cipro™ (Ciprofloxacin by Bayer), Sustiva™ (Efavirenz by Bristol-Meyers) Novir™ (Ritonavir by Abott), Roaccutane™ Isotretinoin by Roche and Avodart™ (Dutasteride by GSK).
Lipophilic compounds with high logP and relatively low melting point (denoted as “grease balls”) often suffer poor aqueous solubility, compromised in vitro/in vivo dissolution leading to poor oral bioavailability. This is further confounded by their poor and variable GI absorption depending on the presence or absence of food, rapid metabolism and execration. It is believed that 30–35% of new APIs are broadly categorized as lipophilic compounds. Dissolving such lipophilic drug molecules in lipid/surfactant, or mixtures of lipids and surfactants bypasses the potential rate limiting step in GI absorption, namely in vivo dissolution. Lipid and surfactant-based drug delivery systems offer a viable option to formulate “grease balls”. Choosing an appropriate formulation strategy would require thorough understanding of the physicochemical properties of the lipophilic compound under investigation as well as the lipid excipients and associated biologicals processes.
Lipid-based systems could come in different shapes and forms; lipid solutions, lipid suspensions, solid lipid nanoparticles, solid dosage forms developed from a liquid or semi-solid lipid, microemulsions, self-micro, or nano-emulsifying drug delivery systems (SEDDS, SMEDDS, and SNEDDS). On the other hand, surfactants have a stronger tendency to associate and form interesting self-assemblies giving rise to colloidal systems such as micelles, reverse micelles, lyotropic liquid crystalline systems (lamellar, hexagonal, reverse hexagonal, cubic), vesicles (liposomes, niosomes, cubesomes, ethosomes, transferosmes, phytosomes and all the other “…….somes” that I may have missed. Doxil™ (doxorubicin HCl by Janssen Cilag), Caelyx™ (pegylated liposomal doxorubicin HCl for Injection by Janssen Cilag), AmBisome™ (amphotericin B by Gilead), Epaxal™ (inactivated hepatitis virus by Janssen-Cilag), and Inflexal ™ (influenza virus vaccination Janssen-Cilag) are examples on marketed liposome-based systems.
This issue of PDT encloses a range of lipid and surfactant-based studies, amongst which are the following shortened titles: enhancing solubility of acyclovir; Glycerol monooleate- and phytantriol-based cubosomes; Innovative liposomal platforms grafted with thermoresponsive polymers; Thermoresponsive eye drops of nanostructured lipid carriers and Pluronic F-127; Cationic niosomes of spermine-derivative cationic lipids; Drug delivery application of proniosome; Influence of different surfactants on the physicochemical properties of elastic liposomes; Transferrin-conjugated nanostructured lipid carriers for brain delivery of paclitaxel; Novel nanoemulsion system optimization with artificial neural networks; Chitosan/lecithin liposomal nanovesicles as an oral insulin delivery system; Norcantharidin-loaded self-nanoemulsifying drug delivery systems; Mucoadhesive niosomal gel for ocular tissue targeting; Nonionic surfactant structure and their effect on drug release; Solid–lipid nanoparticles surface modified for brain targeting; Colistin liposomes for the treatment of P. aeruginosa infection and nanoemulsifying drug delivery system to improve the bioavailability of piroxicam.
Once again, I hope you will find something useful within.
Sincerely,
Raid Alany
School of Life Sciences, Pharmacy and Chemistry, Kingston University London, London, UK
School of Pharmacy, The University of Auckland, Auckland, New Zealand