28. 5. 2009 - THERAPEUTIC SYSTEMS - controlled release of drugs from dosage forms (Drug Delivery Systems)

One of the founders of therapeutic systems in the pharmaceutical industry has become an American company, ALZA Corporation, which in the seventies of last century realized a vision of sophisticated pharmaceutical products with controlled release. For most solutions the principle of an osmotic pump was used, which achieved excellent results in the controlled release of active substances (constant release of active substance per unit time).

Perhaps the best known is the OROS system, for industrial products such as Glucotrol XL and Procardia XL, successfully marketed by Pfizer. The company ALZA later entered the market with transdermal systems.

Among the most successful belong the Nicoderm and the Estraderm patches.

The OROS system is very costly and expensive. The search for other technical solutions has become an engine of progress in pharmaceutical technologies; and matrix, reservoir or the gradual erosion of particulate dosage forms based systems have been developed.

terap2A very popular and a relatively simple method is represented by an enteric-coating, providing decay of tablets or capsules in a neutral or slightly alkaline environment of the small intestine. Onset of action, however, is very slow and this technology is not suitable for a number of active substances.

The availability of modern natural and synthetic hydrophilic polymers, as well as hydrophobic products such as waxes opened new possibilities in solving better quality and cheaper therapeutic systems.

Favea company developed its own formulation, which is based on the gradual hydration of the mixture of a derivative of cellulose with the addition of polymers, which limits the negative effects of gastric acid on the viscosity change while hydration of the celulose.

This is achieved through gradual release and dissolution of active ingredients from dosage forms – tablets. The release is constant and the time of release can be relatively easily set by the number of polymer blends in the tablet.

A good solubility and permeability of the active substance (drug) is Conditional on the functionality of therapeutic systems. BCS (biopharmaceutical Classification System) is in pharmaceutical technology, presented by four classes; the first class includes compounds very soluble in water, with excellent permeability. The fourth class includes limited soluble substances with low permeability and those are completely inappropriate for therapeutic systems.

The main benefit of therapeutic systems is improvement of the bioavailability, eventually the reduction of side effects and reducing the initial high levels of the active substances in the plasma.

tabulka_en_405

The possibility of changes in dosing schedule is also linked to this. Time is once a day, exceptionally twice a day is sufficient. Favea company's first product, which gradually releases active substance for 10-12 hours (test in vitro), were tablets containing Riboflavin (Vitamin B2).

Author: PharmDr. Milan Krajíček