Glycerol palmitostearate

In this study, the influence of several formulation factors on the release kinetics of potassium chloride from directly compressed matrices is investigated. Formulations containing hydrophilic (methylcellulose, carbomer), plastic (polyvinyl chloride) and wax (glycerol palmitostearate) matrix materials at concentrations of 10%, 15% and 20%, and insoluble excipients, were prepared and tested using the USP XXI-NF XVI rotating paddle method. 

Goodness-of-fit analysis applied to release data showed that the release mechanism was described by the Higuchi diffusion-controlled model. Confirmation of the diffusion process is provided by the logarithmic form of an empirical equation (Mt/ M=ktn) given by Peppas. Positive deviations from the Higuchi equation might be due to air entrapped in the matrix and for hydrophilic matrices due to the erosion of the gel layer. Analysis of in vitro release indicated that the most suitable matrices were methylcellulose and glycerol palmitostearate. 

Fig. 2—Potassium chloride release profiles from sustained release matrix tablets (hardness, 7.5-8kp) 10% ( ), 15% ( ), 20% (T) polyvinyl chloride 10% ( ), 15% (o), 20% (V) glycerol palmitostearate.

The results of the release experiments are summarized in Fig. 1 and Fig. 2, which represent the percentage released as a function of time. As expected, the drug was released from tablets more slowly with an increase in polymer content. When 10%, 15% and 20% of carbomer were incorporated into the formulations (Fig. 1), the amount of potassium chloride decreased from 93% to 84-7% and 77.3% respectively at the end of 3 h. Glycerol palmitostearate showed similar results for the concentrations of 10%, 15% and 20%, i.e. the amount released was decreased, in 3 h, from 75.7% to 71.4% and 64.9% respectively (Fig. 2). Similar results were also obtained for polyvinyl chloride and methylcellulose. Carbomer and polyvinyl chloride matrix tablets show an... 

The goodness of fit was evaluated by the residuals and correlation coefficients are given in Table 3. For polyvinyl chloride, glycerol palmitostearate, carbomer and methylcellulose matrix tablets, equation (4) showed a significantly better fit than equations (2) and (3) by the / test. 

As the concentration of polyvinyl chloride and glycerol palmitostearate was increased between 15% and 20%, a non-significant decrease in released amount was obtained, while a slight difference in the amount released was observed beween 10% and 15% of polymer concentration (Table 4). Deviations from the Higuchi equation were observed (Table 3). These positive deviations might be due to the air entrapped in the matrix. Similar results were also obtained with polyvinyl chloride by Desai et al. [14] and Korsmeyer etal. [15]. 

Fig. 4—A plot of the percentage released against the square root of time showing the effect of tablet hardness (matrix material concentration, 15%) polyvinyl chloride, , 3.5 1kp (V) 7.5-8kp glycerol palmitostearate, , 3.5—4 kp, o, 7. 5-8 kp.

Glycerol palmitostearate (Precirol AT05 Gattefosse, Saint Priest, France). 

Glycerin palmitostearate glycerol palmitostearate 2-[(l-oxo-hexadecyl)-oxy]-l,3-propanediyl dioctadecanoate and 1,2,3-propane triol Precirol ATO 5. 

Glycerol palmitostearate (Precirol), beeswax, glycowax, castorwax, aluminium monostearate, carnauba wax, glyceryl monostearate, stearyl alcohol... 

Polymers for a fatty matrix glycerol behenate, glycerol palmitostearate, waxes, cetyl alcohol... 

Glyceryl palmitostearate is manufactured, without a catalyst, by the direct esterification of palmitic and stearic acids with glycerol. 

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