DitropanÒ XL
(oxybutynin chloride) Extended Release Tablets
DESCRIPTION
DITROPAN® XL (oxybutynin chloride) is an antispasmodic,
anticholinergic agent. Each DITROPAN® XL Extended
Release Tablet contains 5 mg or 10 mg of oxybutynin chloride
USP, formulated as a once-a-day controlled-release tablet
for oral administration. Oxybutynin chloride is administered
as a racemate of R- and S-enantiomers.
Chemically, oxybutynin chloride is d,l (racemic) 4-diethylamino-2-butynyl
phenylcyclohexylglycolate hydrochloride. The empirical
formula of oxybutynin chloride is C22H31NO3 · HC1.
Oxybutynin chloride is a white crystalline solid with
a molecular weight of 393.9. It is readily soluble in
water and acids, but relatively insoluble in alkalis.
DITROPAN® XL also contains the following inert ingredients:
cellulose acetate, hydroxypropyl methylcellulose, lactose,
magnesium stearate, polyethylene glycol, polyethylene
oxide, synthetic iron oxides, titanium dioxide, polysorbate
80, sodium chloride, and butylated hydroxytoluene.
System Components and Performance
DITROPAN® XL uses osmotic pressure to deliver oxybutynin
chloride at a controlled rate over approximately 24 hours.
The system, which resembles a conventional tablet in appearance,
comprises an osmotically active bilayer core surrounded
by a semipermeable membrane. The bilayer core is composed
of a drug layer containing the drug and excipients, and
a push layer containing osmotically active components.
There is a precision-laser drilled orifice in the semipermeable
membrane on the drug-layer side of the tablet. In an aqueous
environment, such as the gastrointestinal tract, water
permeates through the membrane into the tablet core, causing
the drug to go into suspension and the push layer to expand.
This expansion pushes the suspended drug out through the
orifice. The semipermeable membrane controls the rate
at which water permeates into the tablet core, which in
turn controls the rate of drug delivery. The controlled
rate of drug delivery into the gastrointestinal lumen
is thus independent of pH or gastrointestinal motility.
The function of DITROPAN® XL depends on the existence
of an osmotic gradient between the contents of the bilayer
core and the fluid in the gastrointestinal tract. Since
the osmotic gradient remains constant, drug delivery remains
essentially constant. The biologically inert components
of the tablet remain intact during gastrointestinal transit
and are eliminated in the feces as an insoluble shell.
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