Biomedical subjects

K Balon

Publications and source records attributed to K Balon.

4 recordsLinked to original sources

PubMed1999

Determination of liposome partitioning of ionizable drugs by titration.

Drug partitioning to liposomes has been suggested as a model for partitioning to biomembranes but has been lacking a rapid analytical assay useful for drug screening. A fast pH-metric titration method for the determination of liposome partitioning of ionizable drugs using small unilamellar phosphatidylcholine vesicles prepared by sonic homogenization has been successfully developed, enabling the use of high lipid-to-drug ratios. Liposome-water partition coefficients of diclofenac and propranolol were determined to study the impact of varying titration parameters, temperature, equilibration time, lipid, and liposome types on the partitioning. To validate this method, the results were compared to literature values generated with different techniques and to pH-metric titration results with large unilamellar vesicles. The rapid pH-metric assay gave liposome partitioning data for the two model compounds which were consistent with other analytical techniques and liposome types.

Chemical Phenomena↗

PubMed1999

Drug liposome partitioning as a tool for the prediction of human passive intestinal absorption.

PURPOSE: Appropriate physicochemical parameters are desired for the prediction of passive intestinal drug absorption during lead compound selection and drug development. METHODS: Liposome distribution coefficients measured titrimetrically and solubility data at pH 6.8 were used to characterize 21 structurally diverse ionizable drugs covering a range from <5% to almost complete absorption. RESULTS: A sigmoidal relationship was found between the percentage of human passive intestinal absorption and a new absorption potential parameter calculated from liposome distribution data and the solubility-dose ratio. In contrast, the human absorption data did not correlate with an octanol-based absorption potential or partitioning data alone. Poor correlations were found between liposome and octanol partitioning of ionic species or nonionic bases indicating the profound differences of the partitioning systems. CONCLUSIONS: Liposome distribution coefficients of ionizable drugs derived by a pH-metric titration were successfully used to calculate a parameter that correlates with the percentage of passive intestinal absorption in humans. Profound differences between liposome and octanol partitioning were found for a highly diverse set of species. This titration technique may serve to generate liposome partitioning data for the selection and optimization of lead compounds and in drug development.

Humans↗

PubMed1977

Deformity of the foot following anterior transfer of the posterior tibial tendon and lengthening of the Achilles tendon for spastic equinovarus.

Twenty-four children with spastic equinovarus deformity due to cerebral palsy were treated by anterior transfer of the posterior tibial tendon and Achilles tendon lengthening. In five patients, the operation was performed on both sides, making a total of 29 feet available for evaluation after an average follow-up of five years. Only 38 per cent of the results were graded "good" or "satisfactory." Sixty-two per cent were rated as "poor" because of valgus, calcaneus or equinus deformity severe enough to require re-operation. The post-operative deformity was generally evident one or more years after surgery, often progressive, and more disabling as well as more difficult to correct than the original condition. Although the percentage of acceptable results was considerably higher for hemiplegic patients than for others in the study, we conclude that in this group and in all other categories of spastic patients anterior transfer of the posterior tibial tendon should not be performed.

Achilles Tendon↗

PubMed1967

[Painful heel].

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Calcaneus↗