DUROS Implant Technology for Chronic Pain Treatment

Just as ALZA Corporation's oral and transdermal technologies can improve therapy by controlling drug delivery over hours or days, the DUROS® was designed to bring the same benefits of continuous therapy for up to 1 year. DUROS® technology is the platform for an implantable drug-dispensing osmotic pump Chronogesic®. The system is shaped as a small rod with titanium housing, which can be as small as a matchstick, designed to release drugs (Fig. IV-37). The water drawn into the engine compartment expands the osmotic agent and slowly and continuously

Figure IV-37. Size of the implantable DUROS® system for continuous opioid delivery. The DUROS® pump conceptually resembles a miniature syringe in which the drug is pushed out in highly controlled, minute dosages. Through osmosis, water from the body is slowly drawn through the semi-permeable membrane into the pump by salt (osmotic agent) residing in the engine compartment (Fig. IV-38).

Figure IV-37. Size of the implantable DUROS® system for continuous opioid delivery. The DUROS® pump conceptually resembles a miniature syringe in which the drug is pushed out in highly controlled, minute dosages. Through osmosis, water from the body is slowly drawn through the semi-permeable membrane into the pump by salt (osmotic agent) residing in the engine compartment (Fig. IV-38).

Duros Technology Dimensions: 44mm L x 3,8mm D

Osmotic Agent Piston Drug Resevolr Orifica

Semipermeable Proprietary Drug

Membrane Formulation

Figure IV-38. Cross section of the miniature cylinder implanted subcutaneouly via an applicator under local anesthesia. Salt in the cylinder attracks water that continuously drives a piston generating pressure to deliver an even viscous potent opioid using three different release rates of 2.5, 10, and 20 /u,g/h displaces a piston to dispense small amounts of drug formulation from the drug reservoir through the orifice (Fig. IV-38). The osmotic engine does not require batteries, switches or other electromechanical parts to operate. The DUROS® system can be used for pain therapies requiring systemic or site-specific administration of a drug. To deliver drugs systemically, the DUROS® system is placed just under the skin, for example in the upper arm, in an outpatient procedure that is completed in just a few minutes using local anesthetic. Removal or replacement of the product is also a simple, quick procedure completed in the doctor's office (Fig. IV-39).

Figure IV-39. The Chronogesic® implanter for subcutaneous placement of the DUROS® system

The non-biodegradable, osmotically driven system is intended to enable delivery of small amount of the potent opioid sufentanil. The DUROS® implant is a miniature cylinder made from a titanium alloy, which protects and stabilizes the drug inside, using ALZA's proprietary formulation technology. Water enters into one end of the cylinder through a semipermeable membrane, and the drug is delivered from a port at the other end of the cylinder at a controlled rate appropriate to the specific therapeutic agent sufentanil.

The DUROS® pump operates like a miniature syringe loaded with a drug inside the drug reservoir (Fig. IV-38). Through osmosis, water from the body is slowly drawn through a semipermeable membrane into the pump by salt residing in the engine compartment. This water fills the pump, which slowly and continuously pushes a piston, dispensing the correct amount of drug out of the drug reservoir and into the body. The osmotic engine does not require batteries, switches or other electromechanical parts in order to operate. The amount of drug delivered by the system is regulated by the membrane's control over the amount of water entering the pump and by the concentration of the drug in the drug reservoir. The DUROS® system can be used for therapies requiring systemic or site-specific administration of a drug. To deliver drugs systemically, the DUROS® system is placed just under the skin, for example in the upper arm, in an outpatient procedure that is completed in just a few minutes using local anesthetic. Removal or replacement of the product is also a simple, quick procedure completed in the doctor's office.

Certain performance characteristics of the DUROS® system cannot be matched by drug delivery pumps on the market today. First, the pump can generate sufficient pressure to deliver highly concentrated and viscous formulations. Second, the system can be engineered to deliver a drug dosage at the desired dosing rate with a high degree of precision, to less than 1/100th of a drop per day on a continual basis. The titanium shell of the DUROS®system protects the drug formulation from degradation by enzymes and its passage through the body. As a result, the DUROS® system can store and release drugs in the body for up to 1 year.

DUROS® implant technology is specifically designed for the long-term delivery of the potent opioid sufentanil. Powered by osmosis, the technology incorporates a miniature titanium cylinder with the size of a match and can provide continuous drug delivery for up to 1 year. The system incorporates several advantages for patients with chronic pain:

1. Continuous Delivery. Chronic conditions often require long-term treatment and multi-day dosing regimens. DUROS® can provide precise delivery with a single application of up to 1 year.

2. Improved Patient Compliance: Success in treatment of chronic pain is highly dependent on patient compliance. DUROS®, which can be applied and removed in an outpatient setting, helps promote compliance.

3. Enhanced Drug Stability: A common concern with long-term drug delivery is how the body's environment will affect stability. The design and non-aqueous formulation of DUROS® enhances drug stability until release (Fig. IV-40).

Figure IV-40. In vitro release rate from four different dosage strengths of the Chronogesic® system (mean ± SD)

Figure IV-40. In vitro release rate from four different dosage strengths of the Chronogesic® system (mean ± SD)

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