Loknete Dr. J D Pawar College of Pharmacy.
A new era in the successful creation of controlled release formulations with many properties to offer an effective drug delivery mechanism began with the introduction of bilayer tablets. Bilayer tablets are superior to conventional mouthwash, sprays, and gels. Therefore, using a bilayer pill for analgesic and anti-inflammatory purposes is rather different. Two incompatible substances can be separated using bi-layer tablets, two treatments can be released successively, or sustained release tablets with an immediate release dose in the first layer and a maintenance dose in the second layer can be made. The flaws of a single layered tablet are addressed by the improved and practical bilayer tablet technology. In order to solve common bilayer issues such layer separation, inadequate hardness, imprecise individual layer control of weight, and cross contamination, this article discusses why Development and production of quality bi-layer tablets must be carried out on unique tablet presses due to issues with the layers, decreased yield, etc. thereby a high production output is needed, utilizing an altered tablet press may not be the best choice for producing a superior bilayer tablet under GMP conditions.
These days, both industrialized and developing nations are moving toward a combine approach to treat various ailments and diseases, such as diabetes, cardiovascular disease, and hypertension, which are long-term treatments. More than 90% of the synthesized phrases are consumed orally. It proves that experimenters primarily drawn to this area and that this formulation class is the most widely used globally. Modified release medication products are designed to maximize remedial authority by providing delayed, continuous medication distribution during the whole dose period, resulting in lower patient compliance and convenience1. Skye Pharma PLC used the bilayer tablet concept in its Geomatrix tablet, which is made up of several layers. The framework permits the integration of many medications in the doseform. The creation of layers from various polymers permits manipulation over multiple ratecont rolling polymers, allowing for various drug delivery methods for one or more drugssuch as bolus release or pH-dependent polymers for targeted drug administration in the GI tract such as bolus release followed by a constant rate or pH-dependent polymers for targeted medication delivery in the GI tract. The manufacturing of bilayered tablets is obviously fraught with a variety of problems. Although it has been noted that Proving how the mechanical strength of stacked tablets has no effect on drug release may improve system characterization by sharing insight on how various layers stick to one another. Tablets with two layers are created using a one layer that releases the drug immediately and a third layer that releases the drug later, either in a sustained release process or as a second dosage2.
Need of bilayer tablets
Ideal characteristics of bilayer tablet
Objectives of bilayer tablets
ADVANTAGES
Types Of Bilayer Tablet
Single Sided Tablet Press
Various types of bilayer presses have been designed over the times. The simplest design is single sided press with both chambers of the double confluent separated from each other. Each chamber in staidness fed or forcefed with a different cream, thus producing the 2 individual layers of the tablet. When the color passes under the confluent, it's at first loaded with the first caste of cream followed by the alternate- caste cream also the entire tablet is compressed in one or two step. This is the most straightforward method of creating a bilayer tablet since the two layers in the color mix slightly at their interface and, in the best situations, connect well enough to prevent caste separation during tablet production.
Double sided tablet press
At most of the double sided tablet press, which automates product control use the contraction force to cover and control the weight of the tablet weights. The effective contraction force wielded on each individual tablet with the help of the contraction system at the main contraction of the subcaste. When necessary, this mechanism helps to adjust thedies' fill depth and reject out the forbearance tablets.
ADVANTAGES
Bilayer tablet press with displacement monitoring
The principle of bilayer tablet press is fundamentally different from the principle of compression force. In this case the accuracy increases with reduced compression force. At higher production speed the risk of capping and separation increases, but can be reduced by sufficient dwell time a tall four compression stages.
ADVANTAGES
Multilayer compression basics
Presses can be designed specifically for multi subcaste contraction grains leads to unforeseen rise in blood attention, still the blood position is maintained at asteady state as the medicine is released from the sustained grains.11
Various Techniques for Bilayer Tablet
1.OROS® push pull technology
This system consist of mainly two or three layer among which the one or more layer are essential of the drug and other layer are consist of push layer. The drug layer mainly consists of drug along with two or more different agents. Therefore, the drug in this drug layer is in a weakly soluble form. Additionally, there are osmotic and suspending agents.
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2.L-OROS tm technology.
This system used for the solubility issue Alza developed the L-OROS system where a lipid soft gel product containing drug in a dissolved state is initially manufactured and then coated with a barrier membrane, than osmot ic push layer and than a semi permeable membrane, drilled with an exit orifice.
3.EN SO TROL technology
Solubility enhancement of an order of magnitude or to create optimized dosage form Shire laboratory use an integrated approach to drug delivery focusing on identification and incorporation of the identified enhancer into controlled release technologies.
4.Duros technology
The system consists from an outer cylindrical titanium alloy reservoir. This reservoir has high impact strength and protects the drug molecules from enzymes. The Duros technology is the miniature drug dispensing system that opposes like a miniature syringe and reglious minute quantity of concentrated form in continues and consistent from over months or year
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5.Elan drug technologies’ Dual release drug delivery system
(Duredas™ Technology) is a bilayer tablet designed to deliver either immediate or extended release of two different medications or varying release rates of the same medication within a single dosage form. Instant release can be achieved through a specific tablet preparation method, which involves using granules along with a modified-release hydrophilic matrix complex arranged as distinct layers within the tablet. The inclusion of a blend of hydrophilic polymers imparts the modified-release characteristics to the dosage form.11,12
Preparation
Bilayer tablets are made with one subcaste of drug meant to be released immediately and the other subcaste intended to release the medication later, either as a prolonged release form or as an alternate solution. Separate layers of each medicine may also be compressed to create bilayer tablets containing two unsuitable medicines. It reduces the surface area where the two layers touch.
Compaction
It is essential to meet conditions like adequate stiffness and a perfect medicines melting profile in order to create a tablet formulation that is acceptable. It can be difficult for formulators to achieve those demands because of the drug's poor flow and distinctive properties, especially with bilayer tablet formulations involving a second compression. The material's bonds and compressibility play a big role in the extent to which it presses.
Consolidation
It is the feature of the material wherein interparticulate interaction (bonding) increases mechanical strength. One of the main factors influencing tablets delaminating was determined to be the compression force on layer 13
Various Approaches of Bilayer Tablets
1. A floating medication delivery device
These are intended to have a low viscosity, so when given, they will float on stomach contents until the system malfunctions or the device absorbs enough fluid to lose its buoyancy and become easy to expel from the stomach through an action that aids the emptying of the stomach. The bilayer tablet's construction allows the drug to be given quickly from one layer, giving it a quick starts of result, while the other layer floats in the stomach.
2.Polymeric Bio adhesive System
In a similar way that the outer layer becomes a thick, sticky substance that sticks to the mucus layer or stomach mucosa, these are designed to absorb liquids after administration. Until the adhesive properties wane, this is meant to promote gastric retention. These have been created as two layers: one with bioadhesive characteristics and the other for prompt amount.
3.Swelling System
For the reason to maintain the ease of taking the lozenge shape, they are designed to be adequately modest in administration. They quickly expand disintegrate, or unfold at ingest to a size that inhibits passage through the pylorus until the necessary quantity of drug has been released. The system might leave the stomach by slowly degrading or splitting into tiny fragments. An instant release layer and a conventional or delayed release layer may be found in a usual bilayer tablet. 13, 14
Evaluation Of Bilayer tablets
General Appearance
The overall look of a tablet, including its visual appeal and quality, is crucial for gaining consumer approval. This encompasses the tablet's dimensions, form, color, whether it has an odor or flavor, surface texture, any physical imperfections, thickness, and the clarity of any associated markings.
Size and Shape
The dimensions and form of the tablet can be specifically detailed and regulated.
Tablet Thickness
The thickness of tablets is a crucial factor in recreating their appearance as well as in the counting process involving filling equipment. Certain filling devices depend on the consistent nature of the tablets as a means for counting. A total of ten tablets were selected, and their consistency was measured with a micrometer.
Weight variation
Established protocols are adhered to as outlined in the approved literature.
Friability
The primary variables that frequently trigger tablets to chip, chop, or break are friction and impact. The friability test tests a tablet's ability to endure abrasion during packaging, transit, and use. It is closely related to tablet hardness handling. For this measurement, the Roche reanimator typically is used. A number of tablets are taken into account and then put into the device, where they roll and are repeatedly hit as they descend six inches with each cycle. The tablets are weighed again after undergoing 100 rotations or four minutes of treatment, and this weight is compared to their initial weight. One measure of tablet friability is the amount of weight lost due to abrasion. A loss of weight not exceeding 1% of the tested tablets is typically deemed acceptable during the friability assessment, and any tablets that are broken or crushed are not collected. Generally, when capping occurs, friability measurements are not taken. Thicker tablets may be less prone to capping, while thinner, larger-diameter tablets frequently exhibit significant cupping, suggesting that tablets with increased thickness experience less internal stress. The weight reduction of the tablet serves as the indicator of variability and is expressed as a percentage. %Friability=1?(lossinweight/ Initial weight) X100
Hardness
The ability of tablets to resist chipping, bruising, or breaking during storage, transport, and use is influenced by their hardness. In the mid-1930s, Monsanto developed and introduced a compact and portable hardness tester. This device is often referred to as the Stokes or Monsanto hardness tester. By applying the force generated via a coil spring perpendicular to the tablet's surface, the instrument finds the force need to crack the tablet. The advanced, newly invented equipment from Cobb Pfizer and Schleuniger is used to assess the force needed smash the tablet Assessing hardness, more commonly referred to as crushing strength, occurs during the tablet manufacturing process and serves to determine whether the tablet press needs adjustments in pressure. A drug that is too soft might not resist handling, while one that is too hard might not dissolve in the allotted amount of time to meet dissolution criteria. during final procedures such as shipping, packing, and coating. With a crushing strength of 4 kg, the force required for crushing the pill is measured in 4 kilograms. typically recognized as the minimum for acceptable tablets.
REFERENCES
Ashish Sonawane*, Yashpal More, Vaibhav Patil, Review on Bilayar Tablet, Int. J. of Pharm. Sci., 2025, Vol 3, Issue 5, 3566-3574. https://doi.org/10.5281/zenodo.15478930
10.5281/zenodo.15478930
