Water-insoluble drugs preparation

The coacervation approach uses heating or chemical denaturation and desolvation of natural proteins or carbohydrates. As much as 85% of water-soluble drugs can be entrapped within a protein matrix by freeze-drying the emulsion prepared in this manner. For water-insoluble drugs, a microsuspension-emul-sion procedure has been suggested as a method of choice to achieve high drug payloads. 

For the preparation of a micellar solution, the water-insoluble drug and lipophilic excipients can be dissolved in a liquid surfactant by mixing at a relatively high temperature (43S 6flntil a clear solution is obtained. If necessary, a cosolvent can be added to aid solubility in the surfactant. Then a water or buffer solution containing hydrophilic excipients is added to the desired volume while mixing. In some cases, the aqueous solution needs to be heated to the same temperature as that > the surfactant to obtain desirable results. 

Atypical Spherazole CR system is a tablet that consists of a sandwiched structure as shown in Figure 22.14. Such a system was prepared by the following procedures The water-insoluble drug itraconazole is layered onto microcrystalline cellulose with Eudragit E100 as a binder to form... 

Controlled-release formulations of acetaminophen, aminopyrine, chlorpheniramine maleate, and salicylic acid that use Eudragit RSPM as a water-insoluble carrier, prepared by the solvent method, have been reported. A novel approach that uses a less soluble derivative of the drug as a carrier was used by Yang and Swarbrick to prepare sustained-release solid dispersions of dapsone. 

Effervescent products of water-insoluble drugs have been manufactured. A successful example is the effervescent activated charcoal preparation suggested in the management of theophylline poisoning. ... 

Emulsions and suspensions are disperse systems that is, a liquid or solid phase is dispersed in an external liquid phase. While emulsions are sometimes formulated from oily drugs or nutrient oils their main function is to provide vehicles for drug delivery in which the drug is dissolved in the oil or water phase. Suspensions, on the other hand, are usually prepared from water-insoluble drugs for delivery orally or by injection, usually intramuscular injection. An increasing number of modern delivery systems are suspensions - of liposomes or of polymer or protein microspheres, nanospheres or dendrimers, hence the need to understand the formulation and stabilization of these systems. Pharmaceutical emulsions and suspensions are in the colloidal state, that is where the particles range from the nanometre size to visible (or coarse) dispersions of several micrometres. 

It is known that the preparation of mierospheres by using 0/W emulsions is not an effieient method for die entrapment of water-soluble drugs as the eompounds rapidly dissolve in the aqueous eontinuous phase and are lost It has been widely aeeepted that the problem of inefficient eneapsulation of water-soluble dmgs ean be overcome by using the double-emulsion solvent-evaporation technique. Water-insoluble drugs are usually satisfactorily encapsulated by the 0/W emulsion teehnique (64, 65). 

Ophthalmic delivery For administration of water-insoluble drugs into the eye, colloidal systems are used. Surface active polymers, such as polyvinyl alcohol, poloxamer, and methylcellulose are often added as particle stabilizers and viscosity enhancers. Particle size in such colloidal systems should not exceed 5-10 pm in diameter. Emulsions, liposomes, and micro- and nanoparticles, all stabilized by surfactants, are used in topical ophthalmic drug delivery [56]. For instance, an ophthalmic preparation of cyclosporin A, Restasis , is an emulsion stabilized by polysorbate 80 and polymer carbomer 1342. 

Wang Y, Yan Y, Cui J, Hosta-Rigau L, Heath JK, Nice EC, Caruso F (2010) Encapsulation of water-insoluble drugs in polymer capsules prepared using mesoporous silica templates for intracellular drug delivery. Adv Mater 22 4293-4297... 

T Niwa, H Takeuchi, T Hino, N Kunou, Y Kawa-shima. Preparations of biodegradable nanospheres of water-soluble and insoluble drugs with d,l-lacti-de/glycolide copolymer by a novel spontaneous emulsification solvent diffusion method, and the drug release behavior. J Control Rel 25 89-98, 1993. 

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