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  • 1
    ISSN: 1573-904X
    Keywords: bisphosphonates (diphosphonates) ; calcium-related disorders ; bone-related disorders ; drug administration ; drug absorption tight junctions ; mannitol
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To validate our hypothesis that a bisphosphonate (BP) having a nitrogen-containing heterocyclic ring on the side chain, and with no hydroxyl on the geminal carbon would possess increased activity, and better oral bioavailability due to enhanced solubility of its calcium complexes/salts and weaker Ca chelating properties. Methods. A novel BP, 2-(2-aminopyrimidinio)ethylidene-l,l-bisphosphonic acid betaine (ISA-13-1) was synthesized. The physicochemical properties and permeability were studied in vitro. The effects on macrophages, bone resorption (young growing rat model), and tumor-induced osteolysis (Walker carcinosarcoma) were studied in comparison to clinically used BPs. Results. The solubility of the Ca salt of ISA-13-1 was higher, and the log βCa: BP stability constant and the affinity to hydroxyapatite were lower than those of alendronate and pamidronate. ISA-13-1 exhibited effects similar to those of alendronate on bone volume, on bone osteolysis, and on macrophages, following delivery by liposomes. ISA-13-1 was shown to have 1.5−1.7 times better oral absorption than the other BPs with no deleterious effects on the tight junctions of intestinal tissue. Conclusions. The similar potency to clinically used BPs, the increased oral absorption as well as the lack of effect on tissue tight junction of ISA-13-1 warrant its further consideration as a potential drug for bone diseases.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-904X
    Keywords: bezafibrate ; hyperlipidemia ; pharmacodynamics ; pharmacokinetics ; sustained release
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. To evaluate the role of different routes and modes of administration of bezafibrate (BZF) on its hypolipidemic activity. We hypothesize that the major sites of BZF action are located presystemically as in other 'gastrointestinal (GI) drugs.' Thus, continuous administration of the drug to the GI tract is expected to augment its efficacy and provides a rationale for an oral sustained release preparation of the drug. Methods. The hypothesis was investigated in three experimentally induced-hyperlipidemia rat models. Models A and B were based on cholesterol-enriched diets and Model C on induced acute hyperlipidemia by triton 225 mg/kg. The pharmacokinetics and the pharmacodynamics of the drug following various modes of administration were examined. Results. In all cases, continuous administration of the drug into the duodenum (IGI) at a dose of 30 mg/kg/day for 3 days (Models A and B) or over 18 hr (Model C) reduced significantly both total cholesterol and triglycerides levels and elevated HDL cholesterol levels in comparison to bolus oral administration of the same dose, as well as in comparison to equivalent intravenous infusion (Model C). Infusion of the drug directly into the portal vein produced an equivalent activity to IGI administration. The pharmacokinetic study showed 100% oral bioavailability, good colonic absorption properties and an indication for an enterohepatic cycle. Conclusions. The results confirm that BZF has a first pass hepatic pharmacodynamic effect. Administration of BZF in a slow release matrix tablet to the rats produced the same magnitude of effect as IGI administration, thus proving the pharmacodynamic rationale for this mode of administration for GI drugs.
    Type of Medium: Electronic Resource
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