A phamacoscintigraphic assessment of drug release from dermal formulations

Full text: The absorption of Plasminogen Activator Inhibitor 2 (PAI-2) from dermal formulations was examined using I- 123 labelled PAI-2. Radioiodination with I-123 sodium iodide was done by a modified iodogen method and the final product purified by gel chromatography. I-123 PAI-2 (active)or sodium iodide (control) was incorporated into the gels to produce a final product containing IMBq/ml. Two different gel formulations were tested. 200 ml (0.2MBq) was applied to both normal (2) and psoriatic skin (8) sites on each volunteer. After 6 hours the dressings were removed and each site was washed with 3 saline soaked cotton buds. Each site was then stripped by consecutive applications and removals of 10 separate, numbered pieces of adhesive tape to remove most of the stratum corneum. Measurement of the extent of absorption of the I-123 PAI-2 was made using both gamma imaging and counting. Images of the skin were made prior to removal, after the washing and following the stripping of the gel from the skin. Gamma counting was performed for each site on the 3 cotton buds used for washing, the occlusive dressings (if used) and the stripping tapes. Results demonstrated that absorption of the I-123 PAI-2 from psoriatic skin is approximately 10 times higher than from normal skin. Formulation 2 which contained the permeation enhancer propylene glycol showed a significantly higher skin absorption, whereas occlusive dressings reduced the mean absorption form 46% to 15%. In summary this novel study demonstrates the usefulness of nuclear medicine techniques in the examination of drug release from topical formulations. Copyright (2002) The Australian and New Zealand Society of Nuclear Medicine Inc