DynaCirc CR®(isradipine)Controlled Release Tablets
DESCRIPTION
DynaCirc CR® contains isradipine, a calcium antagonist. It is available for once-daily oral administration as a controlled release 5 mg and 10 mg tablet for DynaCirc CR® (isradipine). DynaCirc CR® is a registered trademark for isradipine GITS (Gastrointestinal Therapeutic System) tablets.
The structural formula of isradipine is:
Chemically, isradipine is 3,5-Pyridinedicarboxylic acid, 4-(4-benzofurazanyl)-1,4-dihydro-2,6-dimethyl-, methyl 1-methylethyl ester. Isradipine is a yellow, fine crystalline powder which is odorless or has a faint characteristic odor. Isradipine is practically insoluble in water (<10 mg/L at 37ºC), but is soluble in ethanol and freely soluble in acetone, chloroform and methylene chloride.
Active Ingredient: isradipine
Inactive Ingredients: butylated hydroxytoluene; cellulose acetate; hydroxypropyl methylcellulose; magnesium stearate; polyethylene glycol; polyethylene oxide; polysorbate 80; propylene glycol; red ferric oxide; silicon dioxide; sodium chloride; titanium dioxide; yellow ferric oxide.
System Components and Performance
Isradipine is delivered from the DynaCirc CR® (isradipine) Controlled Release Tablet as follows: a semipermeable membrane surrounds an osmotically active drug core. The core is composed of two layers: an “active” layer containing the drug, and a pharmacologically inert but osmotically active “push” layer. After ingestion, the tablet overcoating is quickly dissipated in the gastrointestinal tract, allowing water to enter the tablet through the semipermeable membrane. The polyethylene oxide polymer swells in the osmotic (“push”) layer and exerts pressure against the “active” drug layer, releasing isradipine as a fine suspension through the laser-drilled tablet orifice which has been positioned on the “active” drug layer side. Drug delivery is essentially constant as long as the osmotic gradient remains constant and, after either 5 mg or 10 mg of isradipine is released, gradually falls to a negligible amount. The controlled rate of drug delivery into the gastrointestinal lumen is independent of pH or gastrointestinal motility. The delivery of isradipine in DynaCirc CR® (isradipine) Controlled Release Tablets depends on the existence of an osmotic gradient between the contents of the bilayer core and the fluid in the GI tract. The biologically inert core of the tablet remains intact and, unless it becomes trapped, is eliminated in the feces.
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