Abstract
dc:description.abstractThe effects of polyvinyl acetate (PVA) concentration, drug load, molecular weight of polyethylene glycol (PEG) and pH of the dissolution medium on the in vitro release of theophylline and ibuprofen from mixtures of PEG with 0 - 10 % w/w PVA, liquid-filled into hard gelatin capsules, have been studied. The release of both drugs was prolonged and controlled by the addition of PVA, particularly in concentrations > 2 % w/w. The reproducibility of the results was also found to be satisfactory and consistent with claims made for this type of dosage form. The results of Differential Scanning Calorimetry (DSC) studies showed that theophylline formed a simple mixture with PEG whereas ibuprofen formed a eutectic mixture. In addition, the results of X-ray diffraction studies showed that all systems contained crystalline drug dispersed in the PEG, although the lowest theophylline load (50 mg drug / 550mg base) appeared to only just exceed its solubility in the base. Except for this formulation with the lowest theophylline load, where drug release was better described by first-order kinetics, release profiles were described reasonably well by diffusional models. The effects of the experimental variables are discussed in relation to diffusional models. The ibuprofen formulations exhibited complex behaviour during dissolution which prevented the application of diffusional models. The formation of a drug-rich surface "crust" which was affected by all of the experimental variables, was the most notable feature. The release profiles were describable in general by first-order kinetics. The results of storage tests, which were carried out at -4, 20 and 37 °C and 12 - 14 % and 31 % R.H. for periods of up to 1 year, showed that various changes in release characteristics could occur. Although possible reasons for some of these changes are presented it is obvious that further work is necessary before they can be fully explained.
Degree
thesis:*- Name dc:type.qualificationname
- PhD
- Level dc:type.qualificationlevel
- Doctoral
- Grantor dc:publisher.institution
- De Montfort University
- Year dc:date.issued
- 2000
Author and committee
dc:creator, dc:contributor.*- Author dc:creator
-
- SHEHAB, MUAYAD AHMED