Spray-dried PVAc/Povidone

Fig. 56. Flowability of spray-dried PVAc/Povidone in comparison with some other sustained-release matrix formers...

Fig. 57. Compressibility of two batches of spray-dried PVAc/Povidone in propranolol tablets (Formulation see Table 104)...

Applications of spray-dried PVAc/Povidone 8 2 as sustained-release matrix... 

Spray-dried PVAc/Povidone can be used for the production of sustained-release matrix tablets and pellets. 

The excellent flowability and compressibility of spray-dried PVAc/Povidone makes this excipient particulary suitable for the manufacture of sustained-release tablets obtained by direct compression [647-649]. 

The sustained-release characteristics can be modified by varying the content of spray-dried PVAc/Povidone in the formulation. Figure 58 shows the influence of the amount of on the release of caffeine as a example of a soluble active ingredient. 

Fig. 58. Influence of the amount of spray-dried PVAc/Povidone on the drug release in caffeine sustained-release tablet (160 mg caffeine)...

Fig. 59. Influence of the pH and the ionic strength of the dissolution medium on the release of caffeine tablets (Caffeine + spray-dried PVAc/Povidone 1+1)...

For the production of sustained-release tablets with spray-dried PVAc/povidone as matrix the direct compression technology is recommended. 

If the wet granulation technology is applied spray-dried PVAc/Povidone should be put in the extragranular phase to avoid the wetting of this polymer mixture. Such application is shown in in Table 106 in a formulation of metoprolol sustained-release tablets. 

Polyvinyl acetate is described in the literature as a matrix former in theophylline sustained-release tablets obtained by hot-melt extrusion [646]. In a similar way spray-dried PVAc/Povidone can be applied for the production of tablets and pellets using its excellent flowability. In this case the pulverization of polyvinyl acetate by cryogenic grinding can be avoided and the mixture of the active ingredient with the excipients are applied directly to the melt extruder. 

Recently a spray-dried mixture of 8 parts of polyvinyl acetate (PVAc) and 2 parts of povidone K 30 can be found in the market. It is recommended as matrix for sustained-release tablets obtained by direct compression. In this product povidone has two functions to get a free-flowing polyvinyl acetate powder and to form pores in the tablets. 

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