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About Authors:
Adarsh Shikshan Prasarak Mandal’s, K. T. Patil college of Pharmacy,
Siddhartha Nagar, Barshi Road,
Osmanabad – 413501.

As a very few drugs are coming out of research and development and already existing drugs are suffering the problem of resistance due to their irrational use. Hence, change in the operation is a suitable and optimized way to make the some drug more effective by slight alternation in the drug delivery. 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 with minimum side effects. 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. There are several advantages of sustained release drug delivery over conventional dosage forms like improved patient compliance due to less frequent drug administration, reduction of fluctuation in steady-state drug levels, maximum utilization of the drug, increased safety margin of potent drug, reduction in healthcare costs through improved therapy and shorter treatment period. The basic goal of sustained release is provide promising way to decrease the side effect of drug by preventing the fluctuation of the therapeutic concentration of the drug in the body and increase patient compliance by reducing frequency of dose. This article contains the basic information regarding sustained-release formulation and also the different types of the same.

Reference Id: PHARMATUTOR-ART-1433

A drug delivery system (DDS) is defined as a formulation or a device that enables the introduction of a therapeutic substance in the body and improves its efficacy and safety by controlling the rate, time, and place of release of drugs in the body. This process includes the administration of the therapeutic product, the release of the active ingredients by the product, and the subsequent transport of the active ingredients across the biological membranes to the site of action. The term therapeutic substance also applies to an agent such as gene therapy that will induce in vivo production of the active therapeutic agent. Drug delivery system is an interface between the patient and the drug. It may be a formulation of the drug to administer it for a therapeutic purpose or a device used to deliver the drug. This distinction between the drug and the device is important, as it is the criterion for regulatory control of the delivery system by the drug or medicine control agency. If a device is introduced into the human body for purposes other than drug administration, such as therapeutic effect by a physical modality or a drug may be incorporated into the device for preventing complications resulting from the device, it is regulated strictly as a device. There is a wide spectrum between drugs and devices, and the allocation to one or the other category is decided on a case by case basis. Sustained release (SR) preparations are not new but several new modifications are being introduced. They are also referred to as “long acting” or “delayed release” when compared to “rapid” or “conventional” release preparations. The term sometimes overlaps with “controlled release,” which implies more sophisticated control of release and not just confined to the time dimension.


The following are the rationale of developing SR1, 2, 3
1)      To extend the duration of action of the drug
2)      To reduce the frequency of dosing
3)      To minimize the fluctuations in plasma level
4)      Improved drug utilization
5)      Less adverse effects

Advantages of sustained release dosage forms1, 2, 3
1)      The frequency of drug administration is reduced.
2)      Patient compliance can be improved.
3)      Drug administration can be made more convenient as well.
4)      The blood level oscillation characteristic of multiple dosing of conventional dosage forms is reduced.
5)      Better control of drug absorption can be attained, since the high blood level peaks that may be observed after administration of a dose of a high availability drug can be reduced.
6)      The characteristic blood level variations due to multiple dosing of conventional dosage forms can be reduced.
7)      The total amount of drug administered can be reduced, thus:
·         Maximizing availability with minimum dose;
·         Minimize or eliminate local side effects;
·         Minimize or eliminate systemic side effects;
·         Minimize drug accumulation with chronic dosing.
8)      Safety margins of high potency drugs can be increased and the incidence of both local and systemic adverse side effects can be reduced in sensitive patients.
9)      Improve efficiency in treatment.
·         Cure or control condition more promptly
·         Improve control of condition
·         Improve bioavailability of some drugs
·         Make use of special effects; e.g. sustain release aspirin for morning relief of arthritis by dosing before bed-time.
10)   Economy.

Disadvantages of sustained release dosage forms1, 2, 3
1)      Probability of dose dumping.
2)      Reduced potential for dose adjustment.
3)      Cost of single unit higher than conventional dosage forms.
4)      Increase potential for first pass metabolism.
5)      Requirement for additional patient education for proper medication.
6)      Decreased systemic availability in comparison to immediate release conventional dosage forms.
7)      Poor invitro and invivo correlations.

The general consensus is that controlled release denotes systems, which can provide some control, whether this is of a temporal or spatial nature, or both, of drug release in the body. In other words, the systems attempts to control drug concentration in the target tissue or cells.  Thus, prolonged release or sustained release systems, which only prolonged therapeutic blood or tissue levels of the drug for an extended period of time, cannot be considered as controlled release systems by this definition. They are distinguished from rate-controlled drug delivery systems, which are able to specify the release rate and duration in vivo precisely, on the basis of simple invitro tests. Drug targeting; on the other hand, can be considered as a form of controlled release in that exercises spatial control of drug release within the body. In general, controlled delivery attempts to: 
·         Sustain drug action at a predetermined rate by maintaining a relatively constant, effective drug level in the body with concomitant minimization of undesirable side effects associated with a saw tooth kinetic pattern.
·         Localize drug action by spatial placement of a controlled release system (Usually rate-controlled) adjacent to or in the diseased tissue or organ.
·         Target drug action by using carriers or chemical derivatization to deliver drug to a particular “target” cell type.



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