Retention effect

Lithium intoxication can be precipitated by the use of diuretics, particularly thiazides and metola-zone, and ACE inhibitors. NSAIDs can also precipitate lithium toxicity, mainly due to NSAID inhibition of prostaglandin-dependent renal excretion mechanisms. NSAIDs also impair renal function and cause sodium and water retention, effects which can predispose to interactions. Many case reports describe the antagonistic effects of NSAIDs on diuretics and antihypertensive drugs. The combination of triamterene and indomethacin appears particularly hazardous as it may result in acute renal failure. NSAIDs may also interfere with the beneficial effects of diuretics and ACE inhibitors in heart failure. It is not unusual to see patients whose heart failure has deteriorated in spite of increased doses of frusemide who are also concurrently taking an NSAID. 

A novel sizing strategy utilizes a microparticle system that enhances retention.166 A representative example is a combination of cationic potato starch (DS = 0.04), a metallosilicate hydrosol and AKD. In an approach to combine elevated filler retention, effective sizing and high paper strength, calcium carbonate is reacted with a starch-soap complex and combined with AKD.167168... 

The numerous reasons which can account for various deviations from the ideal FFF retention theory were discussed in the corresponding sections. Here, additional problems are treated which can complicate FFF measurements and significantly distort the results obtained. General requirements for a successful FFF measurement include precise flow control and flow rate precise temperature measurement precise determination of t0 and tr correct relaxation procedure control of sample overloading and integrity and control of mixed normal and steric retention effects as well as wall adsorption control. Some of these complications cannot be avoided so one must correct for these effects, usually in a sem-iempirical and partially very complicated fashion. 

By utilizing polymerization in the miniemulsion system, larger HPG analogues can be created by linking several HPG units to a nanoparticle in order to obtain an optimum diameter of 50 nm [116], This size range is considered to be ideal for drug delivery carriers that may accumulate in tumors or inflamed tissue by the enhanced permeation and retention effect (EPR) [52],... 

In the JET tokamak experience, it is more difficult to separate the retention effects due to different species. In general, regions of high deuterium and... 

Primary drug Secondary drug URINARY RETENTION Effect Mechanism Precautions... 

A number of studies have examined the use of a dendrimer drug carrier to treat a variety of tumors. One approach has been based on the exploitation of the enhanced permeability and retention effect (EPR effect) to localize drug conjugates in tumor tissue. " A second approach has involved the conjugation of a... 

TFA is frequently applied as an additive in LC-MS, for instance in the RPLC separation of peptides (Ch. 16.3.2). TFA is applied as an ion-pairing agent and to mask secondary retention effects of RPLC stationary phases. Without TFA in the mobile phase, the peptides would be almost irreversibly adsorbed. TFA restrlts in significant signal suppression due to both ion-pairing and sirrface-tension effects. The TFA anion more-or-less masks the positive charge on an analyte molecttle at the droplet surface and thereby prohibits lEV of that ion. In the TFA-fix , a post-column addition of propionic acid in 2-propanol (75 25, v/v) is used to counteract the suppression [103-104]. This approach has been found to be successful in some cases, but not in all. 

From the viewpoint of application, QSRR equations in TLC are mainly used for retention prediction. The explanation of the separation mechanism awaits further investigation. With the application of various statistical methods, it is possible to select the primary retention-effect factors from many solute related factors which will offer explanations of separation mechanisms. 

Secondary retention effects residual silanol interactions. —> Use ion pair reagent, or competing base or acid modifier. Trie-thylamine for basic compounds, acetate for acidic compounds. 

If only some of the peaks tail, secondary retention effects, such as residual silanol interactions, may take place. Another possibility is that a small peak is eluting on the tail of a larger peak. If all peaks tail, this may be due to a bad column or build up of contamination on the column inlet frit. 

The antimineralocorticoidal activity of drospirenone is considered as a main benefit. It counteracts the salt and water retention effects of ethinylestradiol, the standard estrogen component in oral contraceptives [33]. 

Fig. 5. Separation of testosterone (T), epitestosterone (E), testosterone TMSi ether (T-D), and epitestosterone TMSi ether (E-D) with an OV-17 column. Conditions 12-foot, 1% OV-17 (on 100-120 mesh Gas-Chrom P) column temperature programmed at 1° per minute from 200° injector, 260° detector, 300° flame detector. The separation of the free steroids is due to a difference in selective retention with an OV-17 phase. The secondary 17 8-OH group of testosterone is less sterically hindered than the secondary 17a-OH group of epitestosterone, and this leads to selective retention of testosterone compared with epitestosterone. The TMSi ethers are eluted in the same order, but the separation is based on a difference in molecular shape, just as observed for OV-1. The derivatives (E-D, T-D) are eluted before the free steroids (E, T) as a consequence of the selective retention effect of the phase for hydroxyl groups. Reproduced from Homing (H13) with permission.

Anderson NH, Hall DJ and Seaman D Spray retention effects of surfactants and plant species, Aspects of Applied Biology, 14 233-243 (1987). 

In some cases, selective accumulation in the target area can be achieved, and this is of major interest in cancer therapy. For example, compared to normal tissue, tumor vessels can take up conjugates with a molecular weight >40 kDa. In addition, the lymphatic system in these areas is unable to provide a full drainage function, and this may lead to an enhanced perme-abihty and retention effect (EPR) of high-molecular weight compounds. Small molecules are not accumulated as they are able to diffuse back into the blood circulation... 

Absorption an irreversible chemical retention effect on surfaces, either liquid or solid. Improperly applied to the dissolution (physical effect) of gases in liquids. 

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