Dissolution studies in organic solvents for evaluating hydrogen-bond matrix of cellulose in the ground mixture

Influence of adsorbents in transdermal matrix patches on the release and the physical state of ethinyl estradiol and levonorgestrel

The drug release from medium molecular weight polyisobutene patches containing adsorbates (drug content: 0.2% ethinyl estradiol, 1.0% levonorgestrel; adsorbent content: 20%, w/w) increased in the order of no adsorbent<titanium dioxide<MCC<crospovidone. This was attributed to differences in drug crystallinity which increased in the order of crospovidone (crystal free)<MCC<titanium dioxide<no adsorbent and the water uptake which increased in the order of no adsorbent (0.1%)=titanium dioxide (0.1%)<MCC (1.6%)<crospovidone (4.8%) at 90% rh. Patches containing adsorbates onto crospovidone were investigated in detail. Increasing the adsorbate's drug loading increased the drug release up to a crospovidone content of 15% (w/w). Patches were crystal free for crospovidone contents ≥ 10% (w/w), which corresponds to a drug loading of crospovidone of 12% (w/w). In conclusion, the incorporation of drug adsorbates onto crospovidone into patches based on polyisobutene significantly increased the drug release (approximately 9.1 times for ethinyl estradiol and 15.4 times for levonorgestrel) and prevented drug recrystallization.

Danazol-beta-cyclodextrin binary system: a potential application in emergency contraception by the oral route

This study explored the potential of beta-cyclodextrin to improve the aqueous solubility and dissolution of danazol, investigated a simple and less expensive method for preparation of a danazol-beta-cyclodextrin binary system, and explored the potential application of a danazol-beta-cyclodextrin binary system as a single-dose emergency contraceptive. Phase solubility analysis indicated formation of a first-order soluble complex with stability constant 972.03 M(-1), while Job's plot affirmed 1:1 stoichiometry. The hyperchromic shift in the UV-Vis spectrum of danazol in the presence of beta-cyclodextrin indicated solubilization capability of beta-cyclodextrin for danazol. The extrinsic Cotton effect with a negative peak at 280.7 nm confirmed the inclusion of danazol in the asymmetric locus of beta-cyclodextrin. (1)H-nuclear magnetic resonance analysis suggested that the protons of the steroidal skeleton of danazol display favorable interactions with the beta-cyclodextrin cavity. The danazol-beta-cyclodextrin binary system was prepared by kneading, solution, freeze-drying, and milling methods. The extent of the enhancement of dissolution rate was found to be dependent on the preparation method. Dissolution studies showed a similar relative dissolution rate (2.85) of the danazol-beta-cyclodextrin binary system prepared by the freeze-drying and milling (in the presence of 13% moisture) methods. In a mouse model, the danazol-beta-cyclodextrin binary system at 51.2 mg/kg (equivalent to a 400-mg human dose) showed 100% inhibition of implantation when given postcoitally. Moreover, the danazol-beta-cyclodextrin binary system is safe up to 2000 mg/kg in the mouse (15.52 g/70 kg human) as a single oral dose. Thus, the danazol-beta-cyclodextrin binary system could serve as a new therapeutic application: an oral emergency contraceptive at a physiologically acceptable single dose.

Disorder and dissolution enhancement: Deposition of ibuprofen on to insoluble polymers

Microcrystalline cellulose (MCC) and cross-linked polyvinylpyrrolidone (PVP-CL) were examined as polymeric carriers to support amorphous ibuprofen (IB). Drug/carrier systems were prepared as physical mixes, and drug was loaded onto the polymers by hot mix and solvent deposition methods. The systems were examined using differential scanning calorimetry (DSC), X-ray powder diffractometry (XRD) and by dissolution testing. PVP-CL reduced drug crystallinity more than MCC and, surprisingly, even very simple mixing of ibuprofen with PVP-CL induced disordering of the drug. Increased ibuprofen dissolution rates were achieved with both polymers, in the order of solvent deposition>hot mixes>physical mixes. The increased dissolution rates could be attributed to a combination of faster dissolution from amorphous ibuprofen, microcrystalline drug deposition on carrier surfaces and polymer swelling. However, no clear relationship was observed between ibuprofen dissolution rates (using first order, Higuchi or Hixson-Crowell relationships) and drug crystallinity.

Differences in the mechanical strength of dried microcrystalline cellulose pellets are not due to significant changes in the degree of hydrogen bonding

The mechanical strengths of oven-dried pellets of microcrystalline cellulose, MCC, prepared by extruder/marumerizer technology are weaker when ethanol/water mixtures are used as granulating solutions than when granulated with water. Previously, the difference in the strengths of these pellet systems were thought to be due to changes in the degree of hydrogen bonding within these systems. This work reports the results of studies using magic-angle-spin nuclear magnetic resonance (NMR), x-ray diffraction and degree of crystallinity, and oxygen combustion calorimetry studies of various MCC systems developed to test this hypothesis. Carbon-13 cross polarization magic-angle spin NMR studies of MCC pellets with and without 10% theophylline showed no differences in the spectra of these systems. X-ray diffraction studies and heats of combustion data obtained from oxygen combustion calorimetry of oven-dried pellets of MCC granulated with either water, deuterated water, or a 70/30 ethanol/water mixture were found to have no significant differences in their diffraction patterns, degree of crystallinity, or internal energies. None of these results provide any evidence that a significant net change in the degree of hydrogen bonding is responsible for the observed changes in the strengths of these systems. It is hypothesized that the strength of these dried pellets may, in part, be due to the conversion of some of the intramolecular hydrogen bonded amorphous fibrils at the surface of the MCC particles to intermolecular hydrogen bonded fibrils with other MCC particles.