Dissolution time

Table 3. Dissolution Time of Dry Alum, Al2(S04)3l4.3H20, and Heat Evolved on Mixing...

Fibers of a diversified draw ratio in the range 2.0-5.2 X were considered, determining the following parameters of their fine structure the crystalline and amorphous orientation functions,and/a, degree of crystallinity, X, and critical dissolution time (CDS) in seconds. The results obtained are listed in Table 11. 

An alternative approach was reported (49) in which tobramycin was directly incorporated into a porcine scleral shield with a 72-hr dissolution time by immersion in a solution of the drug. After implantation in rabbit eyes for up to 8 hr, the shields were removed and the concentration of antibiotic in the corneas and aqueous humor... 

S. Yamamura, F. Aida, Y. Momose, and E. Fukuoka, Analysis of mean disintegration time and mean dissolution time by moment analysis microcalorimetric curves, Drug Dev. Ind. Pharm., 26, 1 (2000). 

Figure 8 Dissolution-time profile of acetaminophen crystals (75 mg, 355-500 pm) in water at 4°C. The crystals were grown at 30°C and at 240 rpm from aqueous solutions containing initially 23.1 g/dm3 acetaminophen and the following concentrations of p-acet-oxyacetanilide a ( ) Zero ( ) 100 mg/dm3 (A) 300 mg/dm3 (O) 500 mg/dm3. (Reprinted with permission from Ref. 6.)...

While batch dissolution methods are simple to set up and to operate, are widely used, and may be carefully and reproducibly standardized, they suffer from the following disadvantages (1) the hydrodynamics are usually poorly characterized, with the notable exception of the rotating disc method, (2) a small change in dissolution rate will often create an undetectable and therefore an immeasurable perturbation in the dissolution time curve, and (3) the solute concentration cb may not be uniform throughout the solution volume V. 

Fig. 14 Dissolution-time profiles for a batch-type dissolution apparatus (A), and a continuous-flow dissolution apparatus (B). (Reproduced with permission of the copyright owner, John Wiley and Sons, Inc., from Ref. 1, p. 476.)...

In pharmaceuticals, NIR is used for, of course, moisture, polymorphic (drug) forms, percent crystallinity, isomer purity, tablet/capsule assay, coating levels, evaluation of dissolution times, and numerous process tests. It is a rapid means for the Food and Drug Administration to check for counterfeit drugs, and for the Drug Enforcement Agency to ascertain what type of materials are impounded in drug raids. ... 

More recently, microwave ovens have been used for sample dissolution. The sample is sealed in a Teflon bottle or a specially designed microwave digestion vessel with a mixture of suitable acids. The high-frequency microwave, temperature (ca. 100-250°C) and increased pressure have a role to play in the success of this technique. An added advantage is the significant reduction in sample dissolution time [25, 26],... 

At such elevated temperatures these and other acids become more corrosive. Materials that digest slowly or will not digest at the atmospheric boiling points of the acids become more soluble so dissolution times are greatly reduced. The aggressive digestion action... 

Performance Indices Quality Factors Optimum E1LB Critical micelle concentration (CMC) Soil solubilization capacity Krafft point (ionic surfactants only) Cloud point (nonionic surfactants only) Viscosity Calcium binding capacity Surface tension reduction at CMC Dissolution time Material and/or structural attributes... 

Dissolution time, tdi (for powder) Particle mass, m Mass transfer coefficient, k Solubility, S Particle radius, r Density, p Hixson-Crowell (cube root) equation t 1 — (tti 1 m0 )1/3 (kS/prJ... 

Dissolution time, tdi (for tablet) Tablet mass, m Diffusivity, D Grain particle size, dp Tablet size, 77 Porosity, e Order-of-magnitude model derived from Fick s and Darcy s laws [6] 2m2 td x2d2pH4Ds(l-s)2... 

Low temperature etching. Our data suggests that, under hydrothermal conditions the rate of pit formation is dramatically reduced, although perhaps not completely stopped, at C = Ccrjt. Etch pits on a natural, hydrothermally-etched quartz surface therefore indicate extended dissolution times, but not necessarily etching at C < Ccrit This is because the rate of etch pit formation even above Ccr t can be significant at elevated temperatures (as shown by crystal R9). However, at low temperatures, formation of etch pits when C > C would be less likely, and natural surfaces etched at low temperature should record the saturation state of the etching fluid. 

The dissolution measurements of the two products (test and reference, pre- and post-change, two strengths) should be made under the same test conditions. The dissolution time points for both the profiles should be the same, e.g., for IR products 15, 30, 45, and 60 min, for extended-release products 1, 2, 3, 5, and 8 hr. 

Because /2 values are sensitive to the number of dissolution time points, only one measurement should be considered after 85% dissolution of the product. 

Mean residence time, mean dissolution time, mean absorption time... 

Riegelman S, Collier P. The application of statistical moment theory to the evaluation of in vivo dissolution time and absorption time. J Pharmacokinet Biopharm 1980 8 509-534. 

Level B utilizes the principles of statistical moment analysis. The mean in vitro dissolution time is compared to either the mean residence time or the mean in vivo dissolution time. Like correlation Level A, Level B utilizes all of the in vitro and in vivo data, but unlike Level A it is not a point-to-point correlation because it does not reflect the actual in vivo plasma level curve. It should also be kept in mind that there are a number of different in vivo curves that will produce similar mean residence time values, so a unique correlation is not guaranteed. 

This category relates one dissolution time point ( 50%, 90%, etc.) to one pharmacokinetic parameter such as cmax, max, or AUC. It represents a single point correlation and does not characterize the shape of the plasma level, which is... 

Gillespie, W.R. and Veng-Pedersen, P., A polyexponential deconvolution method evaluation of the gastrointestinal bioavailability and mean in vivo dissolution time of some ibuprofen dosage forms, /. Pharmacokinet. Biopharm., 13, 289-307, 1985. 

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