Sustained Release Drug Delivery System: A Review

Introduction:

Presently pharmaceutical industries are focusing on development of sustained release formulations due to its inherent boons. Sustained release dosage forms are designed to release a drug at a predetermined rate by maintaining a constant drug level for a specific period of time. The basic rationale of sustained release drug delivery system optimizes the biopharmaceutical, pharmacokinetic and pharmacodynamics properties of a drug in such a way that its utility is maximized, side-effects are reduced and cure of the disease is achieved. Sustained release (SR) preparations are not new but several new modifications are being introduced. Rising number of patent expirations and soaring need for pediatric and geriatric dosage forms are providing a boost to the growth of the market. Growing awareness regarding added benefits provided by sustained release formulations is also stimulating the growth of the market. SR has received most of the attention because of the fact that there is more feasibility in dosage form. The goal of a SR dosage form is to maintain therapeutic blood or tissue levels of the drug for an extended period.

SR:

Sustained Release are Drug Delivery System (DDS) that is designed to achieve a prolonged therapeutic effect by continuously releasing medication over an extended period of time after administration of single-dose of drug. Sustained release formulations significantly reduce dosage frequency and improve patient compliance. Increasing focus on novel drug delivery, R&D and rising adoption of sustained release formulations for treatment of chronic diseases are major factors driving the market. There are many different methods used to obtain a sustained release (Diffusion Systems, Dissolution Systems, Osmotic Systems, Ion-exchange Resin, Matrix Systems etc).

Making the right excipients choice:

Excipients are key ingredients in Sustained release formulations. Several factors must be considered when selecting specific excipients for Sustained -release formulations. Dosage form type and design need to be considered along with the solubility of the API to ensure that the desired dissolution profile can be achieved with a given excipient, and/or that a good in vitro-in vivo correlation is obtainable.

Formulators can, in fact, face many challenges-from achieving desirable dissolution and release profiles for poorly soluble drugs to risk management of dose dumping to the selection of biocompatible materials with the desired Sustained -release properties. 

Sustained -release excipients are excellent solutions to these challenges, some excipients can now offer dual functionality, both controlling the release of the API and providing increased solubility to poorly soluble APIs. 

Several Excipient manufacturers works closely with their customers to understand their specific needs and have developed new solutions to meet Sustained release formulation challenges as they have arisen. They are developing ready-to-use excipients that may provide solutions and support to move existing formulations into new areas, but excipients do not have their own approval pathway. Pharmaceutical companies are hesitant to take the responsibility of toxicology and clinical trials with an untested material and run the risk of jeopardizing approval of their new drug applications.

Rationale of Developing SR DDS:

• To extend the duration of action of the drug
• To reduce the frequency of dosing
• To minimize the fluctuations in plasma level
• Improved drug utilization
• Less adverse effects

Advantages of SR DDS:

• Reduced dosing frequency.
• Dose reduction
• Improved patient compliance
• A constant level of drug concentration in blood plasma
• Reduced toxicity due to overdose.
• Reduces the fluctuation of peak-valley concentration.
• Night-time dosing can be avoided.
• Reduces the side effects. 

Disadvantages of SR DDS:

• Probability of dose dumping
• Reduced potential for dose adjustment.
• Cost of single unit higher than conventional dosage forms
• Increase potential for first pass metabolism.
• The requirement for additional patient education for proper medication
• Poor in vitro and in vivo correlations
• Decreased systemic availability in comparison to immediate release conventional dosage forms.

Future Opportunities:

The oral SRDDS market is the largest piece of the drug delivery market, and there is no sign that it is slowing down. With pharmaceutical companies increasingly turning to drug delivery to extend the revenue-earning lifetime of their biggest products and seeking to tap into the growing elderly population that requires products with a level of ease-of-use and cost benefit. Oral drug delivery provides the definitive break down of the markets. Benefits for short half-life drugs, sustained release can mean less frequent dosing and thus better compliance reduce variations in plasma or blood levels for more consistent result. This would provide the desired impetus to the product. development scientist, facilitating further evolution of research on SRDDS innovations and next-generation product launches. This patent overview provides an updated bird’s eye view survey account on the publications and patents of different novel sustained release delivery that are used for its applications.

Conclusion: 

SRDDS is usually apprehensive with maximum drug availability in attempt to get a maximum rate and extent of drug absorption; however, controls of drug action through formulation also imply controlling bioavailability to decrease drug absorption rates. Oral dosage forms characterize one of the leading-edge areas of sustained release drug delivery system (SRDDS). SR formulations are helpful in increasing the efficiency of the dose as well as they are also improving the patient’s compliance and expediency due to less frequent drug administration. The present overview further provides an insight for assorted commercial platform technology, criteria of drug selection, advance novel research and patents for SRDDS. The SRDDS may be used to deliver drugs at a sustained rate over a period of 24 hours. The dosage form design is for optimizing the delivery of medication to bring about the control of curative effect in the face of uncertain fluctuation and in the vivo environment in which drug release take place. In the future, design of oral SR formulated products used to obtain the desired drug accessibility rate from sustained action dosage form include increasing the particle size of the drug, embedding the drug in matrix, coating the drug or dosage form containing drug or microencapsulation, forming complexes of the drug with material such as ion exchange resins. SR formulations are easy to optimize and tremendously useful in case of the antibiotics in which irrational use of the similar possibly will perhaps result in resistance. I hope that my effort will find a new application.

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About the Author:

Dr. Ajay Kumar Singh, M.Sc. (Gold Medalist), Ph.D. is the author and founder of “Pharma Solutions by Dr. Ajay”.

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