PDF Controlled Release in Oral Drug Delivery

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However, each drug presents its own challenges so please contact us for an informal discussion on how we might be able to help you by combining our formulation and development capabilities together with our wide range of technologies. Soctec is a versatile extended release gastro-retentive platform technology that has been designed to overcome many of the limitations of alternative systems.

Skyepharma has a range of oral drug bioavailability enhancers that use proprietary technologies that act by improving solubility, an essential factor for drug effectiveness, independent of administration route.

Modified-release oral drug delivery

A member of the Vectura Group of companies. Oral Drug Delivery Technologies.

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The larger size of extended-release products may cause difficulties in ingestion or transit through the gut. These problems may result in some drugs, e. Slow-K, causing local tissue damage in patients who have a pathological or drug-induced reduction in gut motility.

The extent of fluctuation in drug concentration at steady state is determined by the relative magnitude of the elimination half-life and the dosing interval. If a drug is given at an interval equal to the elimination half-life, there is a two-fold difference between the maximum and minimum concentrations at steady state. For drugs with short half-lives and with a clear relationship between concentration and response, it will be necessary to dose at regular, frequent intervals in order to maintain the concentration within the therapeutic range.

Higher doses at less frequent intervals will result in higher peak concentrations with the possibility of toxicity. For some drugs with wide margins of safety, this approach may be satisfactory, e. This means that very large fluctuations will occur within a dosing interval, but, in view of the low toxicity of this drug, no difficulty with this approach is encountered provided the concentrations are above the minimum effective concentration during the dosing interval.

On the contrary, clinical efficacy may be enhanced by the transiently high bactericidal concentration of the antibiotic e. Conversely, drugs with long half-lives can be given at less frequent intervals.

Key points

There is generally no advantage in formulating these drugs as extended-release formulations unless a rapid rate of change of concentration during the absorptive phase is responsible for transient adverse effects. The pharmacological effect of some drugs with short half-lives is sustained by various mechanisms:. In these systems, there is a water-insoluble polymer which controls the flow of water and the subsequent egress of dissolved drug from the dosage form.

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Both diffusional and dissolution processes are involved. Cellulose derivatives are commonly used in the reservoir types, while the matrix material may be plastics, e. In these products, the rate of dissolution of the drug and thereby availability for absorption is controlled by slowly soluble polymers or by micro encapsulation.

Once the coating is dissolved, the drug becomes available for dissolution. By varying the thicknesses of the coat and its composition, the rate of drug release can be controlled.


Some preparations contain a fraction of the total dose as an immediate-release component to provide a pulse dose soon after administration. The pellet dosage forms of diffusion- or dissolution-controlled products can be encapsulated or prepared as a tablet.

These products should not be chewed as the coating may be damaged. One of the advantages of encapsulated pelleted products is that the onset of absorption is less sensitive to stomach emptying. The entrance of the pellets into the small intestine where the majority of drug absorption occurs is usually more uniform than with non-disintegrating extended-release tablet formulations.

An example of this type of product is Fefol. The release of drug from these products is controlled by the erosion rate of a carrier matrix. The rate of release is determined by the rate of erosion. An example of this formulation is Sinemet CR. With this product, some patients may experience a later onset of effect after the morning dose, compared to conventional levodopa tablets, because of the delayed release of the drug. The rate of release of drug in these products is determined by the constant inflow of water across a semipermeable membrane into a reservoir which contains an osmotic agent.

The drug is either mixed with the agent or is located in a reservoir. The dosage form contains a small hole from which dissolved drug is pumped at a rate determined by the rate of entrance of water due to osmotic pressure. The rate of release is constant and can be controlled within tight limits yielding relatively constant blood concentrations.

The advantage of this type of product is that the constant release is unaltered by the environment of the gastrointestinal tract and relies simply on the passage of water into the dosage form. The rate of release can be modified by altering the osmotic agent and the size of the hole. An example of this type of product is Adalat Oros. Some drugs can be bound to ion exchange resins and, when ingested, the release of drug is determined by the ionic environment within the gastrointestinal tract.

Oral extended-release products

Examples of this type of product are Duromine containing the basic drug phentermine complexed onto an anionic resin, and MS Contin suspension which uses a polystyrene sulphonate resin. Where a prescriber wishes to transfer a patient from an immediate-release to an extended-release product, generally the equivalent total daily dose should be the same. In some cases, an effective response may be achieved with a lower dose of the extended-release product.

In view of the complexity of extended-release products and the potential for greater variability, both inter- and intra-subject, patients should be monitored to ensure that the anticipated benefit of switching to such products is actually obtained. A wide range of drugs is now formulated in a variety of different oral extended-release dosage forms. It deals with a comprehensive range of topics and life stages, including:. It covers all commonly encountered cardiovascular disorders and every section has been comprehensively updated. In revising this text, the Writing Group has paid special attention to multiple risk factor management and the current evidence-based approach to cardiovascular disease with a list of key studies being included.

For more information about either of these publications, please contact Therapeutic Guidelines Limited, phone or visit www. Reasonable care is taken to provide accurate information at the time of creation. This information is not intended as a substitute for medical advice and should not be exclusively relied on to manage or diagnose a medical condition. NPS MedicineWise disclaims all liability including for negligence for any loss, damage or injury resulting from reliance on or use of this information.

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Forgot password? Article Authors. Introduction Drug products designed to reduce the frequency of dosing by modifying the rate of drug absorption have been available for many years. Advantages Extended-release products offer 3 potential benefits: sustained blood levels attenuation of adverse effects improved patient compliance.