Absorption window

Satellite astronomical observations remove the problems of the atmospheric absorption windows but require more sophisticated orbital spacecraft. Telescopes mounted on aircraft in part can achieve better results but state-of-the-art results are obtained from orbiting satellites. Probably the most successful satellite telescope for public... 

The most important statistic represents the final plateau of the CDF and the area AUCoo of the corresponding PDF between t = 0 and t = oo. It clearly quantifies the extent of the relevant process, which is in proportion to the applied dose D, or a constant fraction or multiple f D of this, in case of overdose, chemical degradation, etc. Proportionality with dose is violated only if the process contains nonlinear or time-dependent steps such as early loss by defecation, absorption windows, chemical degradation, or non-linear presystemic (first-pass) elimination. 

Another important consideration was the fact that the absorption maxima of oxime acrylate monomers could be tuned to the desired wavelength by the selection of desired ketone or aldehyde chromophore from whence the oxime was originally synthesized. In our design, UV photocrosslinking followed dye-sensitized visible polymerization which formed a soft gel. It is very important to be able to choose the absorption window for the crosslinking reaction to prevent interfering absorption, if any, from the residual dye initiator. Acyl oximes as part of the backbone of a photodegrading polymer chain have been studied by Smets [217],... 

In all cases, formation of a bipolaron state coincides with a complete bleaching of the original tt-tt polyene transition, which in effect moves the optical absorption "window" several hundred nm to the red. More recently we have discovered that polaronic state formation (EDG = MeO) can be preferentially controlled if the quantity of oxidizing agent is carefully monitored (25). 

FIGURE 6.1 The barriers that a lipophilic drug has to transverse along the intestinal absorption process (1) dissolution and solubilization in the intestinal milieu, (2) narrow absorption window, (3) unstirred water layer, (4) efflux pumps, (5) intra-enterocyte metabolism, and (6) first pass hepatic metabolism. 

This time controlled release tablet with a designated lag time followed by a rapid release may provide an alternative to site-specific delivery of drugs with optimal absorption windows or colonic delivery of drugs that are sensitive to low pH or enzyme action for the treatment of localized conditions such as ulcerative colitis, Crohn s disease, and irritable bowel syndrome (IBS). Also, by controlling a predetermined lag time of drug from dosage form, the release behavior can be matched with the body s circadian rhythm pattern in chronotherapy. 

The expanded device should be rigid enough to remain intact and survive the gastric mechanical forces. Besides, the rate of drug release should be appropriate to achieve optimal absorption of the drug from its absorption window. ... 

L-Dopa is a prodrug of dopamine and is known as the drug of choice for the treatment of Parkinson s disease. L-Dopa has a narrow absorption window and is actively absorbed from the upper part of the small intestine. The large fluctuations in L-Dopa plasma concentration cause severe side effects. Hence, there is a PK rationale to elevate the extent of absorption while minimizing the maximum plasma concentration (Cmax) obtained, following oral administration of a sustained release (SR) formulation of L-Dopa. 

These results are important in the development of a GRDF to achieve a delicate interplay in PK factors, prolonged absorption, and sustained blood levels for a compound that has a narrow absorption window owing to active transport and a steep pharmacodynamic profile and is suspected to first-pass metabolism. Based on these results, a new expandable GRDF of l-dopa, with different rigid polymeric matrices, was evaluated in healthy volunteers compared to SR formulation (Sinemit CR) (Fig. 2).t l... 

Riboflavin is another narrow absorption window compound that lacks adverse effects and does not affect the gastric motility. It is often used as a model drug to assess the PK aspects of newly developed CR-GRDF in animal and human subjects. 

For most of the drugs, a better delivery system would significantly minimize the fluctuations in blood levels and consequently improve the therapeutic benefit of the drug as well as reduce its concentration-dependent adverse effect. This feature is of special importance for drugs with relatively narrow therapeutic index and narrow absorption window (e.g. L-Dopa). While the... 

Furosemide is a widely used loop diuretic indicated for the treatment of different pathological conditions such as congestive heart failure, hepatic cirrhosis, and chronic renal failure. It has a narrow absorption window and mainly absorbed from the stomach and the upper part of the small intestine. Following administration of furosemide, the natriuretic effect rapidly disperses and is concealed before the next administration. This problematic aspect in furosemide therapy is mostly attributed to the natural homeostatic compensatory mechanisms. Lately, it has been demonstrated that the diuretic and natriuretic effects of furosemide can be significantly improved, following a continuous input (intravenous infusion) compared to immediate release DFs. Beside the narrow absorption window, this pharmacodynamic feature of the drug provides another rationale for the development of a GRDF for furosemide. 

As beta-lactam antibiotics have a narrow absorption window lying in the upper part of the small intestine (actively absorbed by Pept 1), a GRDF can be more beneficial as it can minimize the appearance of these compounds in the colon and thus prevent any undesirable activities in the colon including the development of microorganism s resistance, which is an important pharmacodynamic aspect. ... 

Hoffman, A. Pharmacodynamic aspects of sustained release preparations. Adv. Drug Dehv. Rev. 1998, 33, 185-199. Davis, S.S. Formulation Strategies for Absorption Window. DDT. 10,249,257, 2005. 

The scintillation counter (Sec. 7-7) and the sealed gas proportional counter (Sec. 7-5) are both used in spectrometry. The scintillation counter is better for the very short wavelength region because of its greater efficiency there (Fig. 7-12) in the 1 A-2 A range either counter is suitable. In the long-wavelength region a gas-flow proportional counter is required, because of its thin low-absorption window. 

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