Kinetics of the acid hydrolysis of diazepam, bromazepam, and flunitrazepam in aqueous and micellar systems.
J Pharm Sci
; 80(5): 459-68, 1991 May.
Article
em En
| MEDLINE
| ID: mdl-1880727
ABSTRACT
A kinetic study of the acid hydrolysis of aqueous diazepam, bromazepam, and flunitrazepam was carried out at 25 degrees C using a spectrophotometric method. For diazepam and flunitrazepam, the experimental pseudo first-order rate constant decreased as the acid concentration was increased. The contrary behavior was found in the case of bromazepam. A kinetic scheme that includes the hydrolysis reaction of both protonated and nonprotonated species of the drug can account for these results. Also, the kinetics of the acid hydrolysis of the same drugs in the presence of micellar aggregates [nonionic polyoxyethylene-23-dodecanol (Brij 35); cationic cetyl trymethyl ammonium bromide (CTAB); and anionic sodium decyl (SdeS), dodecyl (SDS), and tetradecyl (STS) sulfate] was studied at 25 degrees C. Negligible effects were observed in the cases of nonionic and cationic micelles. Anionic micelles produced an inhibitory effect in the reaction velocity. This effect increased as the hydrophobic nature of the surfactant increased. All these facts are interpreted quantitatively by means of a pseudophase model.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Bromazepam
/
Diazepam
/
Flunitrazepam
Idioma:
En
Revista:
J Pharm Sci
Ano de publicação:
1991
Tipo de documento:
Article
País de afiliação:
Espanha