Topical delivery preparations

One of the major drawbacks of liposomes is related to their preparation methods [3,4]. Liposomes for topical delivery are prepared by the same classic methods widely described in the literature for preparation of these vesicles. The majority of the liposome preparation methods are complicated multistep processes. These methods include hydration of a dry lipid film, emulsification, reverse phase evaporation, freeze thaw processes, and solvent injection. Liposome preparation is followed by homogenization and separation of unentrapped drug by centrifugation, gel filtration, or dialysis. These techniques suffer from one or more drawbacks such as the use of solvents (sometimes pharmaceutically unacceptable), an additional sizing process to control the size distribution of final products (sonication, extrusion), multiple-step entrapment procedure for preparing drug-containing liposomes, and the need for special equipment. 

The ototopical antimicrobial preparations stated earlier suffice for most cases of otitis externa and selected cases of chronic suppurative otitis. However, these compounds have a limited effect in certain patients with resistant strains of bacteria, drug-induced allergies, or a tympanic membrane perforation that requires administration into the middle ear space. In the last case, ototopical preparations may cause pain because of the acidic pH or the presence of alcohol. Ototoxicity of neomycin, polymyxin B, and colistin is also of concern, and many otolaryngologists prefer topical ophthalmic preparations.f Ophthalmic preparations are discussed in the article Ocular Drug Formulation and Delivery in this volume. 

Tan, Q., Liu, W., Guo, C., and Zhai, G. (2011). Preparation and evaluation of quercetin-loaded lecithin-chitosan nanoparticles for topical delivery, IntJ. Nanomed, 6,1621-1630. 

R. MDORE. In the case of L-Dopa, there are preparations on the market now vdiich inhibit enzymatic degradation. I wander if you might know idiether this material lends itself either to the transdeimal or topical delivery systems ... 

The same authors, hy inserting carhon nanotubes (CNTs) into the potymer structure, were able to prepare a highly effective electro-responsive releasing system (Spizzirri et al., 2013). Here, the CNTs allow the enhancement on the electro-conductivity of the hydrogels and carried out to composite materials suitable as topical delivery device for the release of drugs as consequence of an applied external voltage. 

Before discussing the three categories of delivery device, the nature of the emitted aerosol will be considered. Droplet formation may be characterized in terms of the nature of the propulsive force and the liquid being dispersed, and this topic is dealt with for specific situations in the following sections. However, dry particles, which are delivered from suspension in pMDIs or from DPIs alone or from a blend, must be prepared in respirable sizes. The production of respirable aerosol particles has traditionally been achieved by micronization of the drug [25]. This... 

As pharmaceutical scientists gain experience and tackle the primary challenges of developing stable parenteral formulations of proteins, the horizons continue to expand and novel delivery systems and alternative routes of administration are being sought. The interest in protein drug delivery is reflected by the wealth of literature that covers this topic [150-154]. Typically, protein therapeutics are prepared as sterile products for parenteral administration, but in the past several years, there has been increased interest in pulmonary, oral, transdermal, and controlled-release injectable formulations and many advances have been made. Some of the more promising recent developments are summarized in this section. 

Ointments and Creams Ointments are applied to the skin for topical treatment or to be absorbed into the blood system for delivery to target areas. They are semisofid preparations obtained by mixing the API with selected ointment bases depending on intended use. These bases include petrolatum, paraffin, mineral oil, lanolin, and glycols. Preservatives are often added to ensure the ointments will maintain the recommended shelf life. 

Machida, Y., and Nagai, T. Bioadhesive Preparations as Topical Dosage Forms. In Bioadhesive Drug Delivery Systems (E. Mathiowitz, D.E. Chickering, III, and C.-M. Lehr, eds.), Marcel Dekker, Inc., New York, 1999, pp. 641-657. 

To all these structural modulations, the esterification of 17- and 21-hydroxyl has been added with the aim to prepare oral, topical, spray and delayed-delivery formulations. A huge number of medicines have been marketed from more than 20 basic molecules (Figs. 48-55). Despite the fact that fluorocorticosteroids... 

In general, increased tissue wetness promotes transdermal delivery of both hydrophilic and lipophilic permeants. However, Bucks and Maibach [3] cautioned against too wide a generalization, stating that occlusion does not necessarily increase percutaneous absorption and may not always enhance transdermal delivery of hydrophilic compounds. Further, they warned that occlusion could irritate skin with clear implications for the design and clinical application of transdermal and topical preparations. 

---