Pharmaceutical formulations release

The past decade has seen a dramatic increase in the number of reported applications of neural computing in pharmaceutical formulation [29-32]. Applications now cover a variety of formulations—for example, immediate and controlled release tablets, skin creams, hydrogel ointments, liposomes and emulsions, and film coatings. The following examples are by no means exhaustive, but they show where neural computing has been used successfully in modeling formulations. 

This optimization method, which represents the mathematical techniques, is an extension of the classic method and was the first, to our knowledge, to be applied to a pharmaceutical formulation and processing problem. Fonner et al. [15] chose to apply this method to a tablet formulation and to consider two independent variables. The active ingredient, phenylpropanolamine HC1, was kept at a constant level, and the levels of disintegrant (corn starch) and lubricant (stearic acid) were selected as the independent variables, X and Xj. The dependent variables include tablet hardness, friability, volume, in vitro release rate, and urinary excretion rate in human subjects. 

Nifedipine has a rapid onset of action and a short elimination half-life. A slow-release formulation allows a single daily dose to be prescribed and prevents reflex tachycardia. Newer, second- and third-generation dihydropyridines, have a slower onset and a longer elimination half-life. This makes special pharmaceutical formulations unnecessary. 

Pharmaceutical formulations consisting of poly-a-L-glutamic acid derivatives were prepared by Bonnet-Gonnet (3) and used in the prolonged release of D,L-a-tocopherol. 

Studies conducted by different authors on the release of chemical substances from medical devices, mainly those used for infusing solutions, show that these are potential sources of contamination for pharmaceutical formulations. One of the most studied is diethylhexyl phthalate, the same plasticizer found in PVC infusion bags to give flexibility. The same concerns about the use of PVC bags for the storage of lipids or lipophilic formulations are valid for tubing. 

The testing procedures used in this work have all been well described in the literature (4) and are focused on understanding the compression behavior of the powder samples and the mechanical properties of the resulting compacts. These methods are summarized in Table 1. For brevity, we have limited our initial studies to single component systems, but recognize that more work is needed in the future to understand the complex behavior of multicomponent mixtures. The current work should provide a sound basis for further work on such systems. It is intended that this treatise will enable pharmaceutical formulation scientists to better understand the similarities and differences between the most common grades and types of excipients, and will facilitate the rational selection of excipients for use in the development of immediate release tablet formulations. 

The widespread applicability of di-O-methylisosorbide as a medium for chemical reactions or as a solvent for pharmaceutical formulations is well documented. In some cases, an additive synergism of the solvent and the solute was observed. Some typical examples mentioned include that it acts as a solvent for muscle-relaxant drugs, which are otherwise difficultly soluble,226 and is used for topical and other types of pharmaceutical formulations,227,228 transdermal controlled-release films229 and tapes,230 anthelmintic solutions,231 antimycotic emulsions,232 and for the treatment of skin disorders, such as eczema.233... 

Hydroxy propyl methyl cellulose (HPMC).35 HPMC is a partly O-methylated and 0-(2-hydroxypropylated) cellulose available in several grades that vary in viscosity and extent of substitution. It is used widely in pharmaceutical formulations, especially in oral products, as a tablet binder, in film coating, and as controlled release matrix. Soluble in cold water, it forms a viscous colloidal solution. For a 2% aqueous solution (20°C), viscosity can range from 2.4 to 120,000 mPa-s. High-viscosity grades can be used to retard the release of water-soluble drugs from a matrix. 

Possibly the most effective way to control the distribution of drugs in the human body is to encapsulate them in microscopic or submicroscopic drug carriers of some kind. Although many common pharmaceutical formulations lead to a rapid release of the drug, such drugs are often rapidly removed from the body as well. This means that keeping a drug concentration at a value that provides therapeutic benefit can... 

The reservoir patch has a similar bioadhesive component but pharmaceutical formulations containing certain excipients, such as penetration enhancers and enzyme inhibitors, can be placed in the center of the design. A rate-controlling polymer membrane can be designed to control the drag release. 

Second, the excipient percolation threshold in hydrophilic matrices represents the border between a fast release of the drug (below the threshold) and a drug release controlled by the formation of a coherent gel layer (above the excipient percolation threshold). Therefore, knowledge of this threshold will allow us to avoid the preparation of a number of unnecessary lots during the development of a pharmaceutical formulation, resulting in a reduction of the time to market. 

Goto, T., Tanida, O., Yoshinaga, T., Sato, S., Ball, D. J., Wilding, I. R., Kobayashi, E., and Fujimura, A. (2004), Pharmaceutical design of a novel colon-targeted delivery system using two-layer-coated tablets of three different pharmaceutical formulations, supported by clinical evidence in humans, I. Controlled Release, 97, 31-42. 

Pharmaceutical factors. The amount of drug that is released from a dose form (and so becomes available for absorption) is referred to as its bioavailability. This is highly dependent on its pharmaceutical formulation. With tablets, for example, particle size (surface area exposed to solution), diluting substances, tablet size and pressure used in the tabletting machine can affect disintegration and dissolution and so the bioavailability of the drug. 

Pharmaceutical formulation. Manipulating the formulation in which a drug is presented by modified-release systems can achieve the objective of an even as well as a prolonged effect. 

Blends of different polysaccharides and plasticizers are commonly used in pharmaceutical formulations, particularly those geared for controlled release. Due to its importance, the physical compatibility of these blends was examined by a number of investigators. Sakellariou and associates studied the... 

Thirty years on from the explosion of commercially successful applications of targeted and controlled release pharmaceutical formulations, it is evident that there remains a need for further refinements and innovations in the field of drug delivery. Many of the larger corporations focus on the use of novel technology for extension of a product life cycle however, in many cases solubility and permeability issues limit the application of such technologies. Additional complications arise due to inter- and intrasubject variability, compliance, and chronobiological variation in disease incidence. 

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