A BRIEF REVIEW ON SUSTAINED RELEASE MATRIX TABLETS OF BACLOFEN

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ABOUT AUTHORS:
Singh Surya Pratap*, Soni Shankar Lal, Khinchi Mahaveer Prasad, Gulia Ritu, Namdev Abhisek
Department of pharmaceutics, Kota College of  Pharmacy,
Ranpur, Kota, Rajasthan, India
sp.kota91@gmail.com

ABSTRACT
The objective of the present study was to focus on sustained release matrix tablets of baclofen, for treatment of spastically resulting from multiple sclerosis, flexor spasm and muscular rigidity. Designing effective therapies for Spinal cord injury (SCI) has been a challenging problem because spinal cord injuries are heterogeneous in causality, severity and location of injury.

Effective drug therapy for Spinal cord injury (SCI) first became a reality in 1990 with the finding that the steroid drug methylprednisolone(MP) can significantly improve recovery. Significant advances in recent year, including an effective drug therapy for acute SCI, have improve recovery. In spinal cord injury, pain persist for longer period i.e., several months, hence the long-term treatment is necessary for maintaining the drug concentration in the therapeutic range.

Hence, there is a need of sustained release dosage form. Baclofen,4-amino-3-(4-chlorophenyl)-butyric acid is another structural analog of GABA, which is widely used now a days in the treatment of multiple sclerosis, flexor spasms, muscular rigidity. spinal cord injuries and other spinal cord diseases.

REFERENCE ID: PHARMATUTOR-ART-2298

PharmaTutor (ISSN: 2347 - 7881)

Volume 2, Issue 12

Received On: 22/10/2014; Accepted On: 28/10/2014; Published On: 01/12/2014

How to cite this article: SP Singh, SS Lal, KM Prasad, R Gulia, N Abhisek; A Brief Review on Sustained Release Matrix Tablets of Baclofen; PharmaTutor; 2014; 2(12); 86-98

INTRODUCTION
Oral drug delivery has been known for decades as the most widely utilized route of administered among all the routes that have been employed for the systemic delivery of drug via various pharmaceutical products of different dosage forms. The reasons that the oral route achieved such popularity may be in part attributed to its ease of administration belief that by oral administration of the drug is well absorbed.

All the pharmaceutical products formulated for systemic delivery via the oral route of administration irrespective of the mode of delivery (immediate, sustained or controlled release) and the design of dosage forms (either solid dispersion or liquid), must be developed within the intrinsic characteristics of GI physiology, pharmacokinetics, pharmacodymics and  formulation design is essential to achieve a systemic approach to the successful development of an oral pharmaceutical dosage form.1

RATIONALE OF SUSTAINED AND CONTROLLED DRUG DELIVERY:
The basic rational for controlled drug delivery is to alter the pharmacokinetic and pharmacodynamics of pharmacological active moieties by using novel drug delivery system or by modifying the molecular structure and physiological parameters inherent in the selected route of administration. It is desirable that the duration of drug action becomes more a desing property of a rate rate controlled dosage form and less or not at all a property of the drug molecules inherent kinetics properties. Thus optional design of controlled release systems necessitates a thorough understanding of the pharmacokinetics and pharmacodynamics of the drugs.

SUSTAINED DRUG DELIVERY SYSTEM:2,3,4
Over the past 30 years, as the expense and complication involved in marketing new entities have increased with concomitant recognition of the therapeutics advantages of controlled drug delivery, greater attention has been focused on development of sustained or controlled drug delivery system.

Sustained release technology is relatively new field and as a consequence, research in the field has been extremely fertile and has produced many discoveries.

With many drugs, the basic goal is to achieve a steady state blood level that is therapeutically effective and non-toxic fir an extended period of time. The design of proper dosage form is an important element to accomplish this goal. Sustained release, sustained action, prolonged action, controlled release, extended action, timed release and depot dosage form are term used to identify drug delivery system that are designed to achieve prolonged therapeutic effect by continuously releasing medication over an extended period of time after adminisatration of a single dose. In the case of oral sustained released dosage form, an effect is for several hours depending upon residence time of formulation in the GIT.

Physician can achieve several desirable therapeutics advantages by prescribing sustained release dosage form. Since, the frequency of drug administration is reduced, patient’s compliances can be improved and the drug administration can be made more convenient as well. The blood level oscillation characteristics of multiple dosing form of conventional dosage form is reduced, because more even blood level is maintained in the design of sustained release dosage form. The total amount of drug administered, thus maximum availability with a minimum dose. In addition, the safety margin of high potency drug can be increased and the incidence of both local and systemic adverse effects can be reduced in sensitive patients. Overall, increased administration of sustained release dosage form gives increased reliability.

Not all the drugs are the suitable candidates for the sustained release dosage form. Ideal characteristic of the drug for the sustained release dosage form are;
- Drug should have a shorter half-life as drug with a longer half-life are inherently long acting drugs.
- Drug should be absorbed from large portion of gastrointestinal tract, since absorption must occur through the gut.
- Drug should be having a good solubility profile to be a good candidate for sustained release dosage form.
- Dose of the drug should not be too large, as a larger dose is to be incorporated into sustained release dosage form.

POTENTIAL ADVANTAGE OF SUSTAINED RELEASE DOSAGE FORM:5
- Avoid patient’s compliance problem due to reduced frequency of dosing.
- Blood level oscillation characteristics of multiple dosing of conventional dosage form is reduced because a more even blood level is maintained.
- Employ a less total drug.
- Minimize or eliminate local or systemic side effects.
- Minimize drug accumulation with chronic dosing.
- Obtained less potential of reduction in drug activity with chronic use.
- Improved efficiency in treatment.
- Cure or control condition more promptly.
- Improved control of condition i.e. reduced fluctuation in drug level.
- Improved bioavailability of some drugs.
- Make a use of special effects, e.g sustained release aspect for relief of arthritis by dosing before bedtime.
- Economy.
- Overall, administrations of sustained release form enable increased reliability of therapy.

MODIFIED RELEASE SYSTEM:3
To overcome the potential problem associated with conventional drug therapy, modified release systems were developed and may be divided into four categories,
¨ Delayed release
¨ Sustained release.
¨ Controlled release.
¨ Prolonged release.
¨ Site specific release
¨ Receptor release

Delayed release system
Delayed release systems are those are that use, repetitive intermittent dosage form.

Sustained release system
Sustained release systems are those, which achieves slow release of drug over an extended period of time and in this drug is initially made available to the body in amount to cause the desired pharmacological response.

Controlled release system
An ideal controlled drug delivery system is that which delivers the drug at predetermined rate, locally or systemically for the predetermined period of time.

Prolonged release system
Prolonged release system, prolongs the duration of action without maintaining a constant drug blood level. Thus maintaining constant- drug leveling in blood or target tissue.

Site specific and receptor release system
Site specific and receptor release and targeted release system refers to targeting of the drug directly to a certain biological location.

RECENT TRENDS IN SUSTAINED DRUG DELIVERY SYSTEM:
Sustained release dosage forms are categorized as:
- Single unit dosage form.
- Multiple unit dosage form.
- Mucoadhesive system.

Single unit dosage form:
These refer to diffusion system where the drug is uniformly distributed (dispersed / dissolved) throughout the solid matrix and the release of the drug is controlled or sustained either by incorporating hydrophilic or hydrophobic filler within the matrix or by coating the drug matrix with a swellable or non-swellable polymer film.

These systems can be classified as:

Monolithic system:
If the release rate is controlled or sustained by incorporating hydrophilic or hydrophobic filler within the matrix then the system is called as Monolithic device where the diffusion of drug through the matrix is rate- limiting step.

These are categorized as:
Hydrophobic/Swellable tablet:

Tablet prepared by mixing the drug with hydrophobic/hydrophilic filler appear to extend the release time of the drug from device within the GI tract after oral administration.

Floating tablet or capsule:
Designing of Floating tablet or capsule are called hydro-dynamically balanced drug delivery system is based on the principle that device with gravity lesser than that of the gastric juice of stomach and retain the drug in the proximal region of the GIT.

Semisolid matrix system:
In this system, the hydrophobic carrier occurs in an oily semisolid state where the drug is incorporated and the final mass is usually filled into gelatin capsule to prepare the dosage form.

Coated tablet and Similar Multilayer system:
Multilayer systems are designed in such a way that the drug has to cross a barrier or membrane on its way from the device to the physiological environment. The nature and the number of barriers control the release process.

In the simplest form coated tablet comprised a core containing the drug and a coating layer, which surrounds the core. The core is usually the drug either alone or loaded on to an inert material (hydrophilic or hydrophobic).

Multilayered tablet having two or more distinct layers usually prepared by dry coating technique have also been used to formulate sustained or controlled preparations for water-soluble drugs. In this case, coating which controls the release process covers the core tablet containing the drug only partially.

Osmotic device:
In osmotic device usually an osmotic agent (often with an osmotic adjuvant) is contained within a rigid compartment that is separated from  the osmotic compartment by a partition. In the physiological environment the aqueous fluid penetrates across the membrane and the increased volume within the osmotic compartment pushes the drug out of the device through a delivery orifice.

Multiple unit dosage forms:
It represents a combination of subnets of the dosage forms, the source of which may either be homogeneous or heterogeneous. It offers the advantages of releasing one of the drugs or part of the same drug immediately while remaining drug or parts of the same can be sustained release. These are useful where drug-excipients and drug-drug interactions are inevitable in a single unit dosage form .The various forms are as:
- Micro granules/Spheroids.
- Beads.
- Pellets.
- Microcapsules.

Mucoadhesive systems:
It utilizes principle of bioadhesion for optimum delivery of the drug from the device. Bioadhesion is definable as the occurrence in which one biological substance is adhered to another substance, which may either, be of biological or non-biological origin. If the substance is mucosal membrane the phenomenon is known as mucoadhesion. Conventional controlled release dosage forms described above are restrained localized in selected regions of GIT.Mucoaadhsive systems are suitable to increased the contact time of drug with absorbing membrane and localization of delivery of drug at target sites.

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