Drug release characteristics

A simple example of gel formation is provided by chitosan tripolyphosphate and chitosan polyphosphate gel beads the pH-responsive swelling abihty, drug-release characteristics, and morphology of the gel bead depend on polyelectrolyte complexation mechanism and the molecular weight. The chitosan beads gelled in pentasodium tripolyphosphate or polyphosphoric acid solution by ionotropic cross-hnking or interpolymer complexation, respectively. 

The effect of various chemical modifications on the mechanical properties of reconstituted collagen and the diffusion rates of the steroid medroxyprogesterone was investigated (38). Formaldehyde-treated films, which are heavily crosslinked, have high moduli and low rates of drug release. Films treated with chrome quickly become hydrated in solution and have low moduli and very rapid drug release characteristics. 

Poly(lactic acid) (PLA) has also been added to poly(SA) via melt polycondensation to produce the triblock copolymers poly(lactic acid-Wock-sebacic acid-Wock-lactic acid) (P(LA-block-SA-block-LA)) by Slivniak and Domb (2002). The PLA (d-, l-, and dl-) was incorporated by acetylation and addition to the PSA synthesis. They showed the formation of stable stereocomplexed particles with increased melting points and reduced solubility, and studied the degradation and drug release characteristics of the same (Slivniak and Domb, 2002). The stereocomplexes self-assemble as a consequence of the chirality in the PLA portions of the chains (Slivniak and Domb, 2002). 

Klein S, Rudolph M, Dressman JB. Drug release characteristics of different mesalazine products using USP apparatus 3 to simulate passage through the GI tract. Dissolution Technol 2002 9 6-12. 

Lim HI, Masin D, Madden TD, Bally MB. Influence of drug release characteristics on the therapeutic activity of liposomal mitoxantrone. J Pharmacol Exp Ther 1997 281 566. 

Lim, Y. H., Kim, D., and Lee, D. S. Drug releasing characteristics of thermo- and pH-sensitive interpenetrating polymer networks based on poly(A-isopropylacry-lamide). J. Appl. Polym. Sci. 1997, 64, 2647-2655. 

High gloss Drug release characteristics meet target requirements High (and reproducible) process coating efficiency... 

Figure 16 Comparison of drug release characteristics of pellets coated with an aqueous ethylcellulose dispersion using a laboratory-, pilot-, and production-scale Wurster process.

Table 15 Rank Order Summary of Process Variables Influencing Coating Process Efficiencies and Drug Release Characteristics (Tso)...

As can be seen from the summary provided in Table 14, the processing conditions used clearly influence the ultimate drug release characteristics. On further examination, it was concluded that the major causes of the magnitude of differences in drug release characteristics were primarily due to ... 

Figure 17 Drug release characteristics of pellets coated on various scales of the Wurster process when the laboratory-scale process, used as the basis for scale-up, has been fully optimized.

Kellaway IW, Marriott C. Correlations between physical and drug release characteristics of polyethylene glycol suppositories. J Pharm Sci 1975 64(7) 1162-1166. 

Coalescence of the film coating (determined by means of assessing drug release characteristics before and after imposition of a curing step)... 

A summary of the response variables obtained in this preliminary study are shown in Table 14, and the order ranking for the influence of process variables on the critical responses associated with coating process efficiency and drug release are provided in Table 15. As can be seen from the summary provided in Table 14, there is clearly an influence of the processing conditions used on ultimate drug release characteristics. On further examination, it was concluded that the major causes of the magnitude of differences in drug release characteristics were primarily due to ... 

Modified Release Dosage Forms Dosage forms whose drug-release characteristics of time course and/or location are chosen to accomplish therapeutic or convenience objectives not offered by conventional dosage forms such as a solution or an immediate release dosage form. Modified release solid oral dosage forms include both delayed and extended release drug products. 

Chowdhary, R. K., Shariff, I., and Dolphin, D. (2003). Drug release characteristics of lipid based benzoporphyrin derivative.J. Pharm. Pharm. Sci., 6, 13-19. 

Dissolution Dissolution is important to ensure proper drug release characteristics (in vitro availability) and batch-to-batch uniformity. 

Kawashima, Y., et al. 1991. Preparation of multiple unit hollow microspheres (microballons) with acrylic resin containing tranilast and their drug release characteristics in vitro) and floating behavior in vivo). J Control Release 16 279... 

The degree of ionization under physiologic conditions Product formulation characteristics Disintegration and dissolution rates for solid dosages Drug release characteristics for timed-release preparations Patient factors... 

The study of stability is not restricted to looking at degradation of the active . It is prudent to bear in mind that any degradation of a formulation excipient may lead to a change in the drug release characteristics of the formulation. For example lactose, a frequently used excipient, can undergo anomerisation in solution between its a- and p- forms. It is conceivable that this could take place in the solid state in a formulation stored under extreme conditions. This could be studied by LC (Figure 12.13). 

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