sodium-dodecyl-sulfate and carboxypolymethylene

We have prepared poly(ethylene oxide) (PEO) tablets which have three-layered structure by direct compression. Carbopol (CP) was coated on both sides of the central PEO matrix which contains solid-dispersed nifedipine (NP) in PEG4000. For comparison, physical mixture of PEO with poly(ethylene glycol 4000) (PEG4000) solid dispersion was also prepared. The differential scanning calorimetry (DSC) thermogram and X-ray diffraction (XRD) pattern obtained after 4 weeks of storage indicated that the crystallinity of PEG4000 in solid dispersion only slightly increased upon aging during this storage period. The formation of crystalline domain of NP, PEO or sodium dodecyl sulfate (SDS) was not observed. CP layers decreased the surface area exposed to dissolution medium, and after swelling, they also covered the exposed side area of the tablet. It seems that swelling and morphological change of CP layers minimize the erosional release for rapidly erodible PEO200K (Mw 200,000) and change the NP release to a diffusion-controlled process. For PEO900K (Mw 900,000), initial release rate was slower than that of PEO200K, possibly due to the slower swelling and erosional release from the side of the tablet. Diffusional release seemed to be the dominating mechanism for the release of NP from PEO7000K (Mw 7,000,000) tablet. Physical mixture of PEO and CP delayed the release of NP remarkably. The increase in pH, ionic strength and buffer concentration of the dissolution medium decreased the release rate. The data obtained for capped and blended tablets were fitted using the power law equation to understand the release mechanism. These results provided some useful information on parameters which can be modulated in the design of a controlled release dosage form for NP.

Topics: Acrylic Resins; Calcium Channel Blockers; Crystallization; Delayed-Action Preparations; Drug Carriers; Drug Storage; Hydrogen-Ion Concentration; Nifedipine; Osmolar Concentration; Polyethylene Glycols; Polyvinyls; Sodium Dodecyl Sulfate; Solubility; Surface-Active Agents; Tablets

The release profile of sodium dodecyl sulfate (SDS), a potent microbicide, from a female controlled drug delivery system (FcDDS) made of Carbopol 934P and hydroxypropyl methylcellulose (HPMC) was evaluated using a newly developed in vitro Simulant Vaginal System (SVS). The major parameters involved in the release profiles of SDS were categorized as: (1) formulation variables (total loading weight of intravaginal delivery systems, SDS loading doses in intravaginal delivery systems); (2) intrinsic variables (vaginal fluid secretion rate, vaginal fluid pH); and (3) extrinsic variables (inserting position). In most conditions, about 70% of the loading dose of SDS was released from FcDDS within 6h of application. The release profile showed that concentrations needed for complete human papilloma virus (HPV) inactivation could be obtained within 10 min after the application. It was demonstrated that intrinsic variables (i.e., the rate and pH of vaginal fluid) played an integral role in determining the release profile of SDS, while loading dose of SDS in FcDDS did not significantly affect the percentage of the total amount of SDS released. It can be concluded that FcDDS can be exploited as a controlled delivery device for prevention against sexually transmitted diseases.

Topics: Acrylic Resins; Administration, Intravaginal; Algorithms; Anti-Infective Agents; Buffers; Diffusion; Drug Delivery Systems; Excipients; Female; Humans; Hydrogen-Ion Concentration; Lactose; Methylcellulose; Oxazines; Papillomaviridae; Polyvinyls; Sodium Dodecyl Sulfate