Drug Delivery Systems Overview

The ideal drug delivery system maintains a constant therapeutic drug concentration at the target site for the desired treatment duration.

The repetitive administration of conventional dosage forms aims to achieve and maintain a therapeutic "steady-state" plasma concentration of the drug.

Conventional dosage forms are designed to optimize the rate and extent of drug absorption, maximizing drug bioavailability.

Poor patient compliance is a significant challenge with conventional dosage forms, especially those with short half-lives requiring frequent administration.

Fluctuations in peak and trough plasma drug levels can lead to undesirable side effects or loss of therapeutic efficacy.

Maintaining steady-state drug levels with minimal fluctuations is crucial, especially for drugs with narrow therapeutic indices.

Controlling the rate of drug delivery, sustaining therapeutic activity, and targeting drug delivery to specific tissues are important for overcoming limitations of conventional dosage forms.

Development of new drugs with long half-lives and effective controlled delivery systems are approaches to address challenges of conventional drug therapy.

The process where water is absorbed by a matrix, causing it to expand and change its physical properties.

The rate at which water penetrates the matrix, impacting how quickly the matrix swells and releases the drug.

The speed at which the matrix expands due to water absorption.

The ability of the drug to dissolve in the surrounding liquid (usually water).

The movement of the drug through the swollen matrix, controlled by its concentration gradient.

A special type of polymer that binds to drugs using ions.

The process where a drug molecule bound to an ion exchange resin is replaced by another ion, allowing the drug to be released.

Insoluble drug complexes formed when drugs bind to ion exchange resins.

The movement of a solvent, like water, from a region of lower solute concentration to a region of higher solute concentration.

A controlled-release drug delivery system that uses osmotic pressure to release drug at a consistent rate.

A core containing either an osmotically active drug or an inactive drug with an osmotically active agent, coated with a semi-permeable membrane.

A rigid, semi-permeable membrane surrounding the osmotic core, allowing water to pass through but not the drug.

The rate at which water enters the osmotic core, driving the release of the drug.

A tiny opening in the coating of the osmotic core through which the drug solution is released.

The controlled release of the drug occurs due to the difference in osmotic and hydrostatic pressure on either side of the semi-permeable membrane.

The osmotic pump system delivers drug at a constant rate, independent of environmental factors.

A type of drug release where the entire matrix degrades from the inside out, leading to a gradual release of the drug. Water quickly penetrates the matrix, causing it to swell and break down.

A type of drug release where the matrix degrades only at the surface, creating a consistent release rate. Water penetration is slower than the surface degradation, maintaining the matrix's shape.

A drug release mechanism where the polymer absorbs water, swells, and then releases the drug through a combination of diffusion and dissolution. This approach minimizes a rapid burst of drug release.

The rate at which water penetrates into the polymer matrix.

The rate at which the polymer breaks down or degrades.

The process of drug molecules moving from the matrix to the surrounding environment.

The process where a drug dissolves or separates from the matrix into the surrounding fluid.

The process where the drug is released from the matrix in a sudden, large burst, potentially leading to toxicity.

Osmotic systems are drug delivery devices using osmotic pressure gradients to release medication.

A core containing drug and electrolyte is surrounded by a semi-permeable membrane. Water enters, dissolves the electrolyte, and creates pressure to push out drug solution.

The drug solution is enclosed within a membrane, and an electrolyte surrounding the membrane creates osmotic pressure. This draws water in, compressing the membrane and releasing the drug.

The Elementary Osmotic Pump (EOP) or Oral Osmotic Pump (OROS) dispenses drugs independently of gastrointestinal (GIT) pH and motility.

Water enters the EOP through the semi-permeable membrane, dissolving an osmotic agent and creating pressure. This saturated solution is then released through a delivery orifice.

The EOP relies on water entering through the membrane, so only one diffusion process (water in) is involved.

The EOP's drug release rate is unaffected by factors like agitation, orifice size, pH changes, and hydrodynamic conditions.

A variation of the EOP, with a controlled porosity membrane to regulate drug release. This allows for more precise and localized delivery.

A drug delivery system where a core containing the drug is coated with a semi-permeable membrane. The membrane controls the release of the drug by regulating the diffusion of water into the core, creating an osmotic pressure gradient. This osmotic pressure drives the release of the drug.

Membrane permeability, osmotic pressure of the core, drug solubility in the core, coating thickness, coating component solubility, orifice diameter, and membrane area. These factors influence the rate of drug diffusion and release.

A specialized drug delivery system where a hydrophilic gum swells in the presence of water, creating hydrodynamic pressure. This pressure forces the drug out of a collapsible reservoir, providing a controlled release mechanism.

The surface area of the opening in the system, the nature of the hydrophilic gum, and the permeability of the surrounding fluid. These determine the efficiency of the drug release in a hydrodynamic system.

Drugs with either extremely low water solubility or very high water solubility present challenges for sustained release systems. It's difficult to achieve a controlled release for both scenarios.

Drugs with low water solubility are difficult to incorporate into a sustained release system because they tend to dissolve slowly, hindering the controlled delivery process.

Drugs with very high water solubility and rapid dissolution rates are challenging for sustained release systems because their fast dissolution makes it difficult to slow down the release and absorption.

Physico-chemical properties, including aqueous solubility and pKa, play an important role in the design of controlled release systems. Understanding these properties helps to optimize the release profile of the drug.