INTRODUCTION:

Combination therapy is currently being used to treat many diseases and conditions that require long-term care, along with hypertension, diabetes, and cardiovascular disease, in both developing and developed countries.¹

Orally consumed formulations account for more than 90% of all formulations produced today. It demonstrates that this type of formulation is the most popular worldwide, and the researcher's primary focus is in this direction. The primary purpose of controlled drug delivery is to decrease the number of doses required.²

The novel bilayer tablet is superior to the traditional dosage forms for the positive creation of controlled release formulations. Bilayer tablets can be used to deliver two drugs sequentially, as well as to separate two types of incompatible substances. They can too be used for sustained-release tablets, with the first layer serving as the initial dose and the second layer serving as the maintenance dose. In some circumstances, bilayer-tablet includes two layers (fig 1) of sustained release of different drugs.^3-4

The bilayer-tablet is an enhanced knowledge that addresses the drawbacks of a single-layer tablet. The immediate-release layer supplies the initial dose and includes super disintegrants, which speed up drug release and provide a speedy onset of effect (loading dose), while the sustained-release (maintenance dose) layer releases the medication over a longer period.^5-6

When maximum relief is required rapidly, the biphasic method is used; this is followed by a long period of release. It similarly eliminates the need for a medicine to be administered many times. This kind of medication delivery is most suited for Antihypertensive, antihistamines, analgesics, antipyretics, and antiallergenic medicines are all examples of coronary vasodilators.^6-7

In some bilayer tablets, both layers serve as sustain release layers for some antidiabetic drugs.⁸

Fig 1: Bilayer tablet

For A Variety of Reasons, Tablet Dosage forms with Multi-Layer Layers are Designed:-

· Controlling the rate of distribution of single or two active pharmacological ingredients.⁸

· Using the functional feature of the other layer, separate incompatible active pharmaceutical ingredients (API) and control API release from one layer (such as osmotic property).⁹

· By sandwiching the API layer between one or two inactive layers, the overall surface area accessible for the API layer is increased, resulting in swellable/erodible barriers for customized release.¹⁰

The Goals of Bilayer Tablets Are As Follows: - ^11-17

· Controlling the rate at which a single and two active therapeutic ingredients are delivered.

· To separate incompatible active pharmaceutical ingredients, and near use the functional feature of the outer layer to control API release from one layer.

· Change the overall surface area available for the API layer by sand witching with one or 2 inactive layers to achieve swellable or erodible barriers for modified release.

· To provide fixed-dose mixtures of multiple active pharmaceutical ingredients, extend the lifecycle of a drug product, and create new drug delivery mechanisms, such as chewing gadgets, Floating tablets, and Buccal mucoadhesive delivery devices for gastro-retentive medication delivery.

The Bilayer Tablets Have The Following Advantages:

· Bi-layer execution with a single-layer conversion upgrade kit as an option.

· Now comparison to all other oral dose forms, the price is lower.

· All oral dosage forms have the best chemical and microbiological stability.

The Bilayer Tablets Have the Following Disadvantages:-

· It may be difficult for children and unconscious people to swallow.

· Several drugs resist compression into dense compacts due to their amorphous structure and low density.

Preparation of Bilayer-Tablet:^18-19

A bilayer tablet's first layer is designed to release the medicine right away, while the second layer is designed to release the drug later, as a second dose or in an extended-release form. Bi-layer tablets with two incompatible pharmaceuticals can be made by compressing unique layers of each medicament to reduce the area of contact between two layers.

Compaction:

To develop an adequate tablet formulation, certain parameters must be addressed, such as appropriate mechanical strength and a proper drug release profile.

It may be difficult for the formulator to achieve these circumstances due to the medication's poor flow and compatibility qualities, which will result in capping and/or lamination, especially in the bilayer tablet formulation when the double compression technique is applied. The compressibility and consolidation of material are both factors in compaction.

Compression:

It's a technique for lowering bulk volume by eliminating voids and bringing particles closer together.

Consolidation It's a property of the material in which inter-particle interaction improves mechanical strength (bonding). It was revealed that the compressive stress on layer 1 has a considerable impact on tablet cracking.(fig 2)

Types of Bilayer Tablets:

I. Single punch tablet press:

II. Double punch tablet press:

III. Displacement Monitoring in a Bilayer Tablet Press

IV. Compression Techniques for Multilayer Layers

I. Single punch tablet press:

Over the years, various types of bilayer presses have been developed. The simplest design is a single-sided press with both chambers of the double feeder separated. The tablet's two layers are created by gravity or force-feeding a different powder into each chamber. The first powder layer is loaded when the dye goes through the feeder, following the second powder layer, and finally, the entire tablet is squeezed in one or two steps. When the tablet is formed, the two dye layers mix slightly at their interfaces and, in most cases, link sufficiently to avoid layer separation. This is the most straightforward method for creating a bilayer tablet.

II. Double punch tablet press:

In most double-sided tablet presses that automate production management, the compression force is developed to monitor and adjust the weight of the tablet weight. During the layer's main compression, this compression system applies effective compressive forces to each tablet. This technology aids in the rejection of tolerance tablets as well as the correction of die fill depth as necessary.

III. Displacement Monitoring in a Bilayer Tablet Press

A bilayer tablet press operates on a different concept than a compressive load. When the compressive stress is lessened in this circumstance, the accuracy improves. Capping and separation become more likely as production speeds increase, however, this can be mitigated by allowing enough dwell time in tall four compression stages.

IV. Compression Techniques for Multilayer Layers:

Multilayer compression press can stay developed particularly for this purpose, or a regular double press can be adapted to accommodate multipliers. Sustained-release formulations have long been created using the multilayer tablet principle. To prolong drug release, these tablets feature a fast-release layer and may include players or triple layers.

Various Techniques For Bilayer Tablet:

OROS® Push Pull Technology:

Its method has 2 or 3 layers, one or more of which are required for the medicine and another of which is a pushing layer. Drug layers contain primarily of the drug, as well as two or more distinct agents.(fig 3) As a result, this drug layer contains a poorly soluble drug. Also included are a suspending substance and an osmotic substance. A semi-permeable membrane surrounds a tablet's core.^20-21

Fig 3: OROS® Push Pull Technology

L-oros Technology:

The solubility problem was solved to use this method. Its L-OROS process was built by Alza and involves coating a lipid soft gel product that contains medicine inside a dissolved form with a barrier membrane, an osmotic push layer, and a semi-permeable membrane drilled with an exit hole with a protective layer, an osmotic push layer, and a semi-permeable membrane drilled including an exit hole(fig 4). ²²

Fig 4: L-oros Technology

EN-SO-TROL Technology:

An order of amount increase in solubility otherwise the creation of an optimal dose from Shire labs takes a holistic technique on drug administration, concentrating arranged identifying then incorporating discovered enhancers Exploring technology for controlled-release(fig 5).

Fig 5: EN-SO-TROL Technology

Duros Technology:

An exterior cylindrical titanium alloy reservoir makes up the system. The drug molecules are protected from enzymes by these reservoirs have a strong impact resistance. Exploring technology for controlled release DUROS technology (fig 6) is a micro medicine distribution system that works like a little syringe and dispenses a small amount throughout months or years in concentrated in a consistent and reproducible manner.^23-25

Fig 6: DUROS Technology

Bilayer Tablets Evaluation^26-28

Overall Appearance:

The entire appearance, design aesthetic, and general elegance of a tablet are all factors that influence consumer adoption. Size, shape, color, odor, flavor, particle shape, structural flaws, and the uniformity and readability of any identification mark are all things to think about.

Size and Shape:

Structurally specifying, tracking, and controlling its tablet's size or shape is possible.

Tablet Thickness:

The thickness of the tablet is a crucial factor now both duplicating look now including with equipment for filling. The tablets' uniform thickness is employed as a counting method. in some filling equipment. A micrometer was used to measure the thickness of ten different tablets.

Tablet Hardness:

Tablet hardness influences how resistant they are to fracture or shipment while storing, transport, and handle before use. The hardness of every other formulation's tablet was determined using a Monsanto hardness tester. The hardness was measured in kilograms per square meter.

Friability:

A friability testing is used to assess the hardness of tablets to assess a tablet's ability to tolerate abrasion during packaging, handling, and shipping. The Roche friabilator is commonly used to measure it.

% Friability = [(W0-Wf) / W0] × 100

W0 = Initial weight of tablets, Wf = Final weight of tablets

Uniformity of weight:

Average weight was obtained after twenty tablets were chosen at random. The weight difference was calculated as follows to I. P guidelines.²⁹

Dissolution Studies:

Bilayer tablets are put through in vitro release experiments to simulating gastrointestinal fluid to see if they could deliver the necessary controlled medication. Because the average time for stomach emptying is around 2 hours, drug release tests were conducted for two hours, use For two hours, use USP dissolving testing machine I at 100rpm, 370.5°C, and pH 1.2 buffer (900ml). These dissolving liquids were replaced by 900ml of pH 6.8 buffer solution, and the study was maintained for just an additional 10 hours.

At various time intervals, 5ml of a sample are removed and replace by 5ml of medication dissolving media. A UV spectrophotometer in a multi-component model was used to evaluate the removed samples.²⁹

Stability Studies:

Bilayer tablet is packaged and kept in the appropriate containers period specified by the ICH guideline for expedited trials. After a 15-day interval, the tablets were removed and evaluated for visual flaws, drug content, hardness, friability, and dissolution. To determine the kinetics of deterioration, First-order equations are used to fit the data. To conclude shelf life at 25°C, accelerated stability data is shown using the Arrhenius equation^30-31.

CONCLUSION:

Bilayer tablet is a new type of tablet that has been developed for the successful development of controlled release formulations. It has several qualities that make it a viable drug delivery device. The bilayer tablet is just a more advanced technology that corrects the flaws of a single-layer tablet. Bi-layer tablet is useful when releasing two pharmaceuticals in combination, isolating two incompatible chemicals, and making a prolonged tablet with one layer serving as the initial dose and the second layer functioning as the sustaining dose. So, in the case of Analgesics, antihypertensive drugs, diabetic drugs, anti-inflammatory drugs, and anti-hypertensive drugs whither a mix of therapies is used frequently employed, The utilization of bi-layer tablet is a unique characteristic

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Received on 27.02.2022 Modified on 23.07.2022

Research J. Pharm. and Tech 2023; 16(5):2517-2521.

DOI: 10.52711/0974-360X.2023.00414