Hydrogel Drug Delivery
Hydrogel tablets
The delivery of drugs for pharmaceutical and medical applications is usually achieved through a variety of drug delivery systems such as injections, tablets and sprays. These systems must deliver the correct dose of the drug in an efficient manner, that is: a controlled delivery which maintains the optimal concentration within the bloodstream in order to be therapeutically effective for reasonable periods of time. Typically, such delivery systems produce an initial rise of drug concentration reaching a peak after which it falls off so that another dose is required to maintain drug effectiveness. At times this concentration may rise above the maximum therapeutic range, into the possibly toxic, while at others it falls below the minimum therapeutic level making the drug ineffective.
The ability to release the drug at therapeutically effective levels and maintain these levels for longer periods of time while avoiding such oscillatory behaviour is one of the objectives of a controlled release system. This allows the drug to be administered in a single dose while reducing the possibility of side effects. This requires the design of new systems with an understanding of their release behaviour while optimising their release kinetics.
The majority of controlled release devices consist of drugs dispersed within a polymeric carrier, commonly hydrogels. Hydrogels are three-dimensional, water-swollen structures mainly composed of hydrophilic polymeric networks containing chemical or physical cross-links. Hydrogels can imbibe water or other biofluids with some being able to swell to ten times their original volume. Hydrogels have been used for medical applications for some time. Upon absorption of water a hydrogel changes from its often dry non-swollen state to a gel-like state which exhibits rubbery behaviour with an ability to resemble bodily tissues therefore possessing good bio-compatibility. The medical applications of hydrogels inlude: the use of PHEMA (poly-2-hydroxyethyl methacrylate) for soft contact lenses, PVA (poly-vinyl-alcohol) in artifcial cartilage and Cellulose acetate for artifcial kidneys as well as for biosensors, sutures and dental materials. However, it is their ability to act as drug release devices which is the focus of this report.
The ability to release the drug at therapeutically effective levels and maintain these levels for longer periods of time while avoiding such oscillatory behaviour is one of the objectives of a controlled release system. This allows the drug to be administered in a single dose while reducing the possibility of side effects. This requires the design of new systems with an understanding of their release behaviour while optimising their release kinetics.
The majority of controlled release devices consist of drugs dispersed within a polymeric carrier, commonly hydrogels. Hydrogels are three-dimensional, water-swollen structures mainly composed of hydrophilic polymeric networks containing chemical or physical cross-links. Hydrogels can imbibe water or other biofluids with some being able to swell to ten times their original volume. Hydrogels have been used for medical applications for some time. Upon absorption of water a hydrogel changes from its often dry non-swollen state to a gel-like state which exhibits rubbery behaviour with an ability to resemble bodily tissues therefore possessing good bio-compatibility. The medical applications of hydrogels inlude: the use of PHEMA (poly-2-hydroxyethyl methacrylate) for soft contact lenses, PVA (poly-vinyl-alcohol) in artifcial cartilage and Cellulose acetate for artifcial kidneys as well as for biosensors, sutures and dental materials. However, it is their ability to act as drug release devices which is the focus of this report.