title: [Preparation of verapamil hydrochloride controlled-onset extended-release pellets and its pharmacokinetics in dogs].
abstract: OBJECTIVE
  To prepare verapamil hydrochloride controlled-onset extended-release pellets (VH-COERP) and study its release behavior in vitro. To compare the pharmacokinetic characteristics and bioavailability in six Beagle dogs after oral administration of VH-COERP and verapamil hydrochloride delayed-release pellets (VH-DRP) as reference.
  
  
  METHODS
  The core of VH-COERP were prepared in the fluidized bed (mini-glatt) by spraying water solution containing drugs onto sucrose-starch pellets with hydroroxy propyl methyl cellulose (HPMC) as the inner coating swelling layer and ethylcellulouse aqueous dispersion as the outer coating controlled layer. Through modifying the coating level of inner and outer layer, the VH-COERP with the optimized cumulative release profile was obtained. The concentration of VH in plasma of six dogs and its pharmacokinetic behaviors after oral administration of VH-COERP and VH-DRP at different times were studied by RP-HPLC. The pharmacokinetic parameters were computed by software program 3P97.
  
  
  RESULTS
  The lag time, the release behavior and the amount of VH from VH-COERP within 24 hours were not influenced by the pH of dissolution medium and post-process, but obviously influenced by the different kinds of added material in swelling layer and the coating level of the inner swelling layer and the outer controlled layer. In vitro the lag time of release profile of VH from VH-COERP was 5 h and then VH was extended release from VH-COERP in the following time. Compared with the VH-DRP, VH-COERP in vivo has an obviously lag time (4 h) , Tmax was also delayed (8 h) and the relative bioavailability was (94.56 +/- 7.64)%.
  
  
  CONCLUSIONS
  The release profile of VH from VH-COERP was shown to be extended-release after an conspicuous lag time in vitro and in vivo. So the drug can be taken by the patient before bed time and begin to work at the morning.
authors.affiliation: Institute of Pharmaceutics, China Pharmaceutical University, Nanjing 210038, China.
authors.forename: Zhi-peng
authors.initials: ZP
authors.lastname: Chen
authors.forename: Yan-yu
authors.initials: YY
authors.lastname: Xiao
authors.forename: Hong-xuan
authors.initials: HX
authors.lastname: Chen
authors.forename: Xi-jing
authors.initials: XJ
authors.lastname: Chen
authors.forename: La-rui
authors.initials: LR
authors.lastname: Li
authors.forename: Jia-bi
authors.initials: JB
authors.lastname: Zhu
mesh_terms: D000284:Administration, Oral; D000818:Animals; D001682:Biological Availability; D002121:Calcium Channel Blockers / Q000008:administration & dosage / Q000493:pharmacokinetics*; D002482:Cellulose / Q000031:analogs & derivatives / Q000737:chemistry; D003692:Delayed-Action Preparations; D004285:Dogs; D004355:Drug Stability; D065347:Hypromellose Derivatives; D008747:Methylcellulose / Q000031:analogs & derivatives / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D014700:Verapamil / Q000008:administration & dosage / Q000737:chemistry / Q000493:pharmacokinetics*
chemical_list: D002121:Calcium Channel Blockers; D003692:Delayed-Action Preparations; D065347:Hypromellose Derivatives; C013517:ethyl cellulose; D002482:Cellulose; D008747:Methylcellulose; D014700:Verapamil