Performance delay formulations

The historical developments in delay formulations have been traced by G. Weingarten (Ref 133, p 254), who also tabulated a wealth of performance data... 

Burning rate is of great significance in the case of pyrotechnic formulations as it is indicative of their functional performance. For example, characteristics such as luminosity, IR output etc. are closely related to the burning rate. Similarly, in a pyrotechnic delay formulation, the length of the delay column is decided in the light of the burning rate of the formulation. 

Densities of the fuel, oxidizer and other ingredients decide the densities of formulations. Density of the formulation determines its weight that can be accommodated in a particular volume. The density becomes one of the important criteria in ammunition where specified performance in terms of burning time, delay or luminous output is required in a limited space or column. 

In a nutshell, the performance of weapons and munitions increases with the use of nanosized particles because of the increased surface area and enhanced heat transfer resulting in reduced ignition delay, burn time, improved mechanical properties and high density-specific impulse. Further, formulations based on micron-sized materials with a wide distribution suffer from defects such as slow energy release, incomplete combustion and inability to support rapid combustion which can be overcome with the use of nanoparticles or nanomaterials [102]. 

Nano sized energetic materials possesses desirable combustion characteristics such as high heats of combustion and fast energy release rates. Because of their capability to enhance performance, various metals have been introduced in solid propellants formulations, gel propellants, and solid fuels. Besides, shortened ignition delay and burn times, enhanced heat transfer rates, greater flexibility in design... 

By definition, sustained release formulations differ pharmaceutically and pharmacokinetically from the innovator drug. Delayed or sustained release oral formulations are used for chronic therapy, and may have two principal advantages (a) reduction in dose frequency (and thus, hopefully, improved compliance see Chapter 21) and (b) reduction of Cmax for a standard AUC, which can improve tolerability when adverse events are plasma concentration-related. The demonstration of bioequivalence usually hinges on the following factors (a) equivalence of AUC to an innovator drug at steady state (b) the absence of any chance of dose dumping (c) consistency of performance from dose to dose [see 21CFR320.25(f)]. 

Controlled release products, including those with delayed, sustained, or extended release, are designed for reduced frequency of dosing, reduced absorption variability, improved efficacy, or improved safety over immediate release formulations. In 2008, the controlled release market was estimated at US 21 billion globally and is anticipated to increase to US 29.5 billion in 2017. In the past, controlled release products have been developed to protect innovators from generic erosion of immediate release products while improving patient compliance or product performance. Innovators are now seeking earlier entry of controlled release products to increase patient benefit and sales. ... 

The pharmacokinetic performance of a drug influences the construction of a formulation. This has nowadays led to a dominance of drug delivery systems that provide a controlled or modified release of the drugs, defined as extended or delayed release. Release-controlling polymers are used to build up a barrier that prevents immediate release of a compound. In this way high peak plasma concentrations of drugs are avoided and usually only one dose per day is necessary. The characteristic properties of the formula are evaluated in in vivo tests where blood samples are analyzed often by extremely sensitive bioanalytical methods. 

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