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  • propranolol  (2)
  • monolayers  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Ion-Pairing Interactions between 99MTc-Based Myocardial Imaging Agents and Oleic Acid (1996)
    Springer
    Pharmaceutical research 13 (1996), S. 316-323 
    Details
    ISSN: 1573-904X
    Keywords: myocardial perfusion imaging agents ; DMPE ; DEPE ; tetrofosmin ; Myoview® ; ion-pairing ; monolayers ; model membranes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Purpose. The purpose was to test the hypothesis that ion-paired facilitated transport is of importance in successful myocardial uptake of cationic imaging complexes. In vitro ion-pairing interactions between oleic acid and seven cationic technetium-99m complexes based on the ligands l,2-bis[bis(2-ethoxyethyl) phosphino ethane] (tetrofosmin), l,2-bis(dimethyl phosphino ethane) (DMPE) and l,2-bis(diethyl phosphino ethane) (DEPE) has been studied. The complexes studied were: [99mTc O2 (tetrofosmin)2]+ (commercially available as myocardial perfusion imaging kit, Myoview®), [99mTc O2 (DMPE)2]+, [99mTc O2 (DEPE)2]+, [99mTc C12 (DMPE)2]+, [99mTc C12 (DEPE)2]+, [99mTc (DMPE)3]+ and [99mTc (DEPE)3]+. Methods. Ion-pairing interactions were monitored using a rotating diffusion cell containing a solid supported liquid membrane and by formation of lipid monolayers. Results. Depletion of complex from the donor phase into an isopropyl myristate model membrane was generally in proportion to distribution coefficient and transfer to the receptor compartment was in all cases very small. However, by the inclusion of 5%w/v oleic acid, which is used in myocardial metabolism, partitioning was enhanced by amounts which varied depending on the tendency to form complex/oleate ion-pairs. Transfer to the receptor compartment was increased for most complexes when given sufficient time to diffuse through the membrane. The complex [99mTc O2 (tetrofosmin)2]+ appeared to form particularly stable ion-pairs with oleic acid. Monolayer formation also indicated ion-pairing interactions. Conclusions. The results suggested that whether or not a complex is taken up by the myocyte may depend on its ability to ‘hitch a ride’ by ion-pairing with the myocytes energy source—a molecule of long chain fatty acid.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1016067820450
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  • 2
    Electronic Resource
    Electronic Resource
    Enantioselective retardation of rac-propranolol from matrices containing cellulose derivatives (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 307-312 
    Details
    ISSN: 0899-0042
    Keywords: stereoselective release ; stereoselective dissolution ; propranolol ; enantiomers ; cellulose derivatives ; tablet matrices ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dissolution characteristics of propranolol enantiomers from tablet formulations containing cellulose, or one of eight cellulose derivatives, were determined under a range of conditions. The derivatives examined were: cellulose tris(phenylcarbamate) (1), cellulose tris(2,3-dichlorophenylcarbamate) (2), cellulose tris 2,4-dichlorophenylcarbamate (3), cellulose tris(2,6-dichlorophenylcarbamate) (4), cellulose tris(2,3-dimethylphenylcarbamate) (5), cellulose tris(3,4-dichlorophenylcarbamate) (6), cellulose tris (3,5-dichlorophenylcarbamate) (7), cellulose tris(3,5-dimethylphenylcarbamate) (8). In water at 25°C, the release rates of (-)R-propranolol were generally greater than those of (-)-S-propranolol, although these differences were not always statistically significant; only compounds 5 and 8 demonstrated significant enantioselectivity. Using compound 8 in further experiments, statistically significant stereoselective dissolution of propranolol HCl was observed in buffer pH 7.4 at 25°C (intrinsic dissolution rates: 0.41 ± 0.01 mgcm2min-1 for R-propranolol and 0.30 ± 0.02 mgcm2min-1 for S-propranolol; P = 0.003). The cumulative amounts of enantiomers released at every time point were also found to be statistically significant (mean ratio R:S 1.25 ± 0.05). The observed low stereoselectivity of 8 with propranolol base was probably attributable to low solubility in pH 7.4 buffer, although stereoselective release did increase with time. This suggested that there is a relationship between stereoselectivity and contact time in an aqueous environment. Results also suggested that increased temperature may affect the release process as well as stereoselective interactions of 8 with individual enantiomers. To conclude, differential release of rac-propranolol from cellulose derivative matrices has been demonstrated, which supports the principle of stereoselective retardation as a potential means of stereoselective drug delivery for solid dosage forms. Chirality 9:307-312, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Direct resolution of propranolol and bupranolol by thin-layer chromatography using cellulose derivatives as stationary phase (1997)
    New York, NY [u.a.] : Wiley-Blackwell
    Chirality 9 (1997), S. 139-144 
    Details
    ISSN: 0899-0042
    Keywords: thin-layer chromatography ; propranolol ; bupranolol ; enantiomers ; cellulose derivatives ; chiral stationary phase ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Cellulose triphenylcarbamate derivatives have been used as stationary phases for resolution of the enantiomers of the β-blockers propranolol and bupranolol by TLC. The derivatives examined were: cellulose trisphenylacarbamate (1), cellulose tris(2,3-dichlorophenyl carbamate) (2), cellulose tris(2,4-dichlorophenyl carbamate) (3), cellulose tris(2,6-dichlorophenyl carbamate) (4), cellulose tris (2,3-dimethylphenyl carbamate) (5), cellulose tris(3,4-dichlorophenyl carbamate) (6), cellulose tris(3,5-dichlorophenyl carbamate) (7), and cellulose tris(3,5-dimethylphenyl carbamate) (8). A variety of mobile phases were used to achieve useful separations and the effects of solvent polarity are also discussed. The best resolution of rac-propranolol was obtained on CSP 8 (RfR = 0.26, RfS = 0.06, α = 4.33) in mobile phase hexane:propan-2-ol (80:20 v/v). The best resolution of rac-bupranolol was obtained on CSP 5 (RfR = 0.29, RfS = 0.09, α = 3.22) in mobile phase hexane:propan-2-ol (80:20 v/v). These results demonstrated the potential of cellulose triphenylcarbamates as chiral stationary phases in TLC and indicate that this is potentially a useful method for the direct, simple, and rapid (within 30 min) resolution of racemates in the analytical control of enantiomeric purity. Physical aspects such as problems in cracking of the CSP, adhesion to plate, and interference of spot detection due to triphenylcarbamate chromphores are also discussed, along with the method employed to overcome them. Chirality 9:139-144, 1997. © 1997 Wiley-Liss, Inc.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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