Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Viscosity suppository bases

Among newly developed colon-specific drug delivery systems, pressure-controlled delivery capsules (PCDCs) [161] can be mentioned. Their mechanism of action is based on the relatively strong peristaltic waves taking place in the colon and leading to an increased luminal pressure. They consist of a capsular-shaped suppositories coated with a water-insoluble polymer (ethyl cellulose). Once taken orally, PCDCs behave like an ethyl cellulose balloon, because the suppository base liquefies at body temperature. In the upper GI tract, PCDCs are not directly subjected to the luminal pressures since sufficient fluid is present in the stomach and small intestine. The reabsorption of water in the colon provokes an increase of the luminal content viscosity. As a result, increased intestinal pressures directly affect the system via colonic peristalsis. Consequently, PCDCs mpture and drug release in the colon take place. [Pg.454]

As the suppository base is heated before moulding, certain effects can be noted which are unique to this type of medication. Testosterone dissolves when hot in the semisynthetic excipient Witepsol H, to give, on cooling, crystals of about 2-3 /rm in diameter. After dissolution in theobroma oil, the dmg does not crystallise on cooling but remains dissolved as a solid solution. In the former case, high absorption rates are obtained, while in the latter poor absorption is achieved. Because of the effect of particle size on the viscosity of suspensions (see section 7.4.4) it is preferable to avoid the incorporation of ultra-fine crystals as the resultant melt of suspension has a higher viscosity than those produced from coarser crystals. [Pg.387]

Controlled release by increasing the viscosity of the suppository base has been studied with morphine. [Pg.194]

When silica is used, it should be considered that the release of aqueous soluble to very soluble active substances may be reduced. Silica increases the viscosity of the base which may impair the transport of the active substance to the interface between water and fat, thereby impairing active substance release. For water-soluble active substances, crossing the interface is rate determining (Sect. 16.2.4). For this reason the amount of silica has to be limited to 1 % of the weight of the active substance. A negative influence of anhydrous colloidal silica on active substance release is evident for amounts above 1.5-2 % of the suppository base [8i]. Concentrations above 1.5-2 % are used only for suppositories with an intentionally delayed release profile. [Pg.201]

Choosing the lowest possible temperature for pouring shortens the solidification time and consequently the period in which the active substance may settle. A low temperature would also benefit the homogeneity during the filling process if the suppository base would be more viscous at this lower temperature. In practice this effect on base viscosity is not often seen (see Sect. 11.4.4) and therefore it is not a valid issue in relation to the filling process. [Pg.213]

Other uses of hydrogenated vegetable oil type I include use as a viscosity modifier in the preparation of oil-based liquid and semisolid formulations in the preparation of suppositories, to reduce the sedimentation of suspended components and to improve the solidification process and in the formulation of liquid and semisolid fills for hard gelatin capsules. ... [Pg.800]


See other pages where Viscosity suppository bases is mentioned: [Pg.209]    [Pg.151]    [Pg.1306]    [Pg.1308]    [Pg.4067]    [Pg.14]    [Pg.273]    [Pg.824]    [Pg.209]    [Pg.659]    [Pg.824]    [Pg.194]    [Pg.824]    [Pg.14]    [Pg.762]    [Pg.385]    [Pg.201]   
See also in sourсe #XX -- [ Pg.387 ]




SEARCH



Suppositories

Suppository bases

© 2024 chempedia.info