Tablet (pharmacy)

❖ Introduction:

A unit dose of one or more medications is contained in solid dosage forms, which are typically designed for oral administration and are known as TABLETS. They continue to be a popular dosage form due to the advantages they offer to both manufacturers and patients. These advantages include simplicity and economy in preparation, stability, and convenience in packaging, shipping, and dispensing. Tablets are appreciated by patients for their accuracy in dosage, compactness, and ease of use.

Tablets come in various shapes, with the most common being discoid, although they can also be round, oval, oblong, cylindrical, and triangular. The size and weight of tablets may vary depending on the quantity of drug substance they contain & intended method of administration.

❖ Advantages:

1. Accuracy in dose.
2. Increased physiological activity, physical and chemical stability.
3. The ease of administering.
4. Economic production on a large scale.
5. Simple to handle, and transport.
6. Special forms, such as sustained-release pills, help patients comply.

❖ Disadvantages:

1. Unsuitable for patients who cannot swallow, including newborns and youngsters.
2. A slower beginning of action than with liquids, oral medications, and parenterals.

❖ Types of tablets:

a) Compressed tablets:

In addition to medication or medications, compressed tablets typically include a variety of pharmaceutical additives, such as following:

1. Diluents are fillers that provide a formulation volume it needs to create tablets of proper size.
2. Binders or adhesives that help the formulation’s particles stick together so that a granulation can be created & integrity of the finished tablet is maintained.
3. Disintegrates, also known as disintegrating agents, which encourage breaking up of tablets into smaller particles after administration to facilitate quick medication access.
4. Sheen-coated tablets are made with anti-adherents, glidants, lubricants & other lubricating substances that increase material flow into tablet dies, lessen wear on punches & dies, prevent fill material from adhering to punches & dies. Tablets may have different coatings after compression. Compression can be used to create tablets for administration via oral, buccal, sublingual, and vaginal routes.

b) Multiply compressed tablets:

The loaded material is compressed more than once to create tablets that have been multiply compressed. The outer tablet is shell, & inner tablet is core. Due to physical and chemical incompatibilities, each layer contains a distinct therapeutic ingredient.

c) Sugar-coated tablets:

A colored sugar layer may be applied to compressed tablets. After being swallowed, the coating soon dissolves because it is h20 soluble. The sugarcoats shield medicine inside from outside elements & act as a defense against unpleasant tastes and odors.

d) Film-coated tablets:

In comparison to compressed tablets coated with a thin sugar coating, film coated pills are more enduring, less cumbersome, and need less time to apply.

e) Gelatin coated tablets:

Tablets that are coated in sugar are a recent innovation. The ground-breaking item, gelcap, is a compressed tablet in shape of a capsule that makes it possible for the coated product to be around one-thirdsmaller than a capsule containing an equivalent amount of powder. In comparison to unsealed capsules, gelatin coating makes swallowing easier and is more tamper-evident.

f) Enteric coated tablets:

Tablets with an enteric coating have a delayed release function. They are made to be ingested through the intestines, where the tablets dissolve and allow for absorption of the medication.

g) Buccal & sublingual tablets:

Tablets for buccal and sublingual use are flat, oval, and designed to dissolve in the buccal pouch or under the tongue for oral mucosal absorption. They allow for oral absorption of medications that are either poorly absorbed by GIT & eliminated by gastric juice.

i) Chewable Tablets:

Chewable tablets are designed to disintegrate quickly and smoothly when chewed and dissolved in the mouth. They typically have a creamy base, often flavored and colored with mannitol. Examples of chewable tablets include Alka Seltzer Original and Extra Strength tablets.

 j) Molded Tablets:

Some tablets are prepared using a molding process, such as tablet triturates, instead of compression. These tablets are usually soft, soluble, and designed for rapid dissolution.

k) Dispensing Tablets:

The use of dispensing tablets has ended. Because pharmacists used them to compose prescriptions, they might be better known as compounding pills. They were not given to patients directly.

❖ Bilayered Tablets:

Over past decade, there has been a growing interest in developing dosage forms that combine two or more (API) in a single unit, known as bilayer tablets. This approach is gaining popularity in the pharmaceutical industry due to its potential to enhance patient convenience and compliance. Several pharmaceutical companies are currently working on bilayered tablets for various reasons, including patent extension, therapeutic benefits, and marketing advantages. Bilayer tablets are innovative drug delivery systems that allow combination of two & more drugs in a single unit.

➢ Types of Bilayer Tablets:

The term bi-layered tablets containing subunits that may be either the same (homogeneous) or different (heterogeneous).

 A. Homogenous Type:

When release patterns of medications differ from one another, bilayers tablets are preferred. Bilayers tablets enable design & control of release & dissolving characteristics. A layer of medication meant for immediate release is combined with a second layer of medication intended for later drug release, either as a second dose or in an extended release form, to create bilayer tablets.

Fig 1: Bilayered tablets same drug but different release pattern

B. Hetero-genous Types:

The sequential release of two medications in combination and separation of two incompatible compounds are both suited for bilayer tablets.

                          Fig 2: Bilayered Tablets with 2-different drugs.

➢ Advantages of Bilayer Tablets:

1. Ability to combine different release rates (Immediate Release – IR and Sustained Release-SR) in a single tablet, making them suitable for chronic conditions that require repeated dosing.
2. Enhanced patient convenience and compliance due to a reduced daily dosing frequency compared to traditional delivery systems.
3. Incorporation of two different drugs in the same dosage form, which can be beneficial for combination therapies.
4. Separation of incompatible components, minimizing physical and chemical incompatibilities.
5. Effective in addressing drug degradation issues.
6. Reduced pill burden for patients, as multiple medications can be combined into a single tablet.
7. Maintenance of physical and chemical stability of active ingredients.
8. Ensured potency and dose accuracy.

➢ Approaches of Bilayer Tablets:

1. Multi-layer tablets with two and three component systems, allowing for different drug release profiles.
2. Compression-coated tablets, where one tablet is encapsulated within another.
3. Inlay tablets, which involve a partial coating surrounding a core tablet.

❖ Multilayered tablets, such as bi-layer (two-layer) or tri-layer (three-layer):

Tablets, are designed to administer two or more active pharmaceutical ingredients simultaneously, even when these ingredients are incompatible with each other. Formulating a multilayered tablet allows the pharmacist to combine different granulations, and these layers are compressed to create a single tablet with distinct layers, often having different colors to make it visually distinctive. During the compression process, it is crucial to implement dust extraction to prevent contamination. Each layer undergoes gentle compression as individual components are laid down, preventing the granules from mixing in case the machine vibrates. This manufacturing approach ensures that the incompatible active ingredients are delivered together in a single tablet while maintaining their individual integrity.

                                            Fig.3: Bilayer tablets, Trilayer tablets,

Compression coated tablets are specific types of tablets with two distinct components: an internal core and an outer coating. This type of tablet is particularly suited for use as a repeat-action tablet, as the outer layer provides initiating force & core is a small, porous tablet prepared on one turret, which is mechanically transferred to a larger die cavity on another turret, where coat material is filled to about half the cavity, followed by the core tablet, filling the remaining space, and compression force being applied. The core tablet is frequently coated with an enteric polymer to inhibit quick release of both layers. This coating prevents medication from being released in the stomach while allowing for a controlled release of the first dose from the exterior sugar coating.

                                                      Figure 4: Core-coated tablets.

Inlay tablets are a sort of layered tablet where the top surface of the core tablet is totally exposed rather than the core tablet being completely encircled by a coating. The core tablet is then placed on top of coating material, which has only been filled to the bottom of the die chamber during preparation. When compression force is applied, some of the coating material is displaced to form sides and fully compress the entire tablet. This approach results in a tablet with a distinctive layered appearance where the top surface of the core is visible.

                                                    Fig.5: Inlay tablets.

➢ The need for bi-layer Tablets: 

1. To administer fixed-dose combinations of various Active Pharmaceutical Ingredients (APIs), to lengthen the shelf life of drug products, to develop new buccal/mucoadhesive delivery method.
2. To regulate the amount of one or two separate active medicinal components that are delivered at the same time in a single tablet.
3. To build swellable/erodible barriers for modified release by sandwiching the API layer between one or two inactive layers, which will change the total surface area available for the API layer.
4. To keep the active components of pharmaceuticals apart from one another.

➢ Advantages of Bilayer Tablets:

1. Bilayer execution with a single-layer conversion kit is optional.
2. Less expensive than alternative drug types.
3. More durable in terms of bacteria and chemicals than other dose forms.
4. Coating techniques can be used to hide offensive odors and harsh tastes.
5. Easily swallowed and less likely to become stuck in the throat.
6. Well suited for industrial production.

➢ Disadvantages of bi-layer Tablets:

• Disadvantages of bi-layer Tablets:

1. Due to their amorphous makeup and low density, some medications resist compression into dense compacts.
2. Encapsulation and coating may be necessary for medications with unpleasant scents, those with bitter tastes, and those that are oxygen-sensitive.
3. Children and people who are unconscious find it difficult to swallow.
4. It may be difficult to create and manufacture tablets for drugs with poor wetting, slow dissolving, and optimal absorption higher in GIT while still guaranteeing acceptable drug bioavailability.

➢ Ideal Characteristics of Bilayer Tablets: 

1. Bilayer tablets must be visually appealing and devoid of flaws, including chips, fractures, discoloration, and contamination.
2. They must be strong enough to endure mechanical shocks during manufacture, packaging, shipping, and use.
3. In order to maintain their physical properties over time and provide predictable and repeatable release of therapeutic ingredients, bilayer tablets should display chemical and physical stability.
4.  They ought to have a shelf life for chemical stability.