12. TABLETS IN PHARMACEUTICS

TABLETS: A TEACHER’S COMPREHENSIVE GUIDE

Welcome, future pharmaceutical scientists and manufacturing professionals!

Tablets are solid unit dosage forms of medicaments with or without suitable diluents and prepared either by moulding or compression. According to the Indian Pharmacopoeia, pharmaceutical tablets are solid, flat, or biconvex discs, unit dosage form, prepared by compressing drugs or a mixture of drugs, with or without diluents.

A dosage form can be defined as the physical form of a dose of a chemical compound used as a drug or medication intended for administration or consumption. The dosage form is the combination of active pharmaceutical ingredients (APIs) and excipients in the formulation.

As a pharmacy educator with years of experience teaching pharmaceutics and industrial pharmacy, I have observed that students often find tablet technology overwhelming. Let me tell you: Tablets are the most widely used dosage form in the world—mastering their formulation and manufacturing is essential for every pharmaceutical professional.

In this comprehensive guide, I will walk you through the fundamentals of tablets—their types, merits, demerits, coating methods, manufacturing processes, excipients, defects, and evaluation tests. By the end of this article, you will have a thorough understanding of tablet technology and its importance in pharmaceutical manufacturing. Let us begin!

Dpharmguru’s exam insights:

Tablets are frequently tested in pharmacy exams. Remember: Tablets are solid unit dosage forms. They are classified into uncoated, coated, and modified tablets. Coating objectives include taste masking, protection, and enteric release. Manufacturing methods include direct compression, wet granulation, and dry granulation. Evaluation tests include weight variation, hardness, friability, disintegration, and dissolution. These are classic exam questions!

5.1. TABLETS

5.1.1. Ideal Properties of Tablets

• It should be attractive having its own identity and free from defects, such as cracks, chips, contamination, discolouration, etc.
• It should have chemical and physical stability to maintain its physical integrity over time.
• It should prevent any alteration in chemical and physical properties of medicinal agent(s).
• It should withstand mechanical shocks encountered during its production, packaging, shipping, and dispensing.
• It should release the medicament(s) in the body in a predictable and reproducible manner.

5.1.2. Types of Tablets

• Uncoated Tablets: Oral tablets, Chewable tablets, Sublingual/Buccal tablets, Lozenge tablets, Soluble tablets, Effervescent tablets, Hypodermic tablets, Vaginal tablets, Implants
• Coated Tablets: Sugar coated tablets, Film coated tablets, Enteric coated tablets, Press coated tablets
• Modified Tablets: Sustained release tablets, Extended release tablets, Fast dissolving tablets, Double layered tablets

5.1.3. Merits of Tablets

• They are unit dosage forms that provide an accurate, stable dose with greatest precision and least content variability
• They are easy to use, handle, and carry by the patient
• They are attractive and pleasing in appearance
• They are the most stable dosage form with respect to their physical, chemical, and microbiological attributes
• Their manufacturing cost is low as compared to other dosage forms
• Their packaging and shipping are comparatively easy and cheap
• They can be coated to mask the unpleasant taste and odour
• They are more suitable for large scale production than other oral dosage forms

5.1.4. Demerits of Tablets

• Drugs which are amorphous in nature or have low density character are difficult to compress
• Hygroscopic drugs cannot be suitably formulated
• Drugs having poor wetting properties and slow dissolution profile are difficult to formulate
• Drugs having a bitter taste require special treatment like coating
• Drugs sensitive to oxygen may require special coating and packaging
• High dose drugs are difficult to formulate as tablets
• Liquid drugs are difficult to formulate as tablets
• Swallowing of tablets, especially by children and critically ill patients, is very difficult

5.2. COATED TABLETS

Coated tablets are those tablets that have an additional layer of coating added to them. A tablet coating is a covering over a tablet which is used to mask the taste, make it easier to swallow, or protect the active medication inside.

5.2.1. Objectives of Coating

• To mask the taste, odour, colour of the drug
• To provide physical and chemical protection to the drug
• To protect the drug from the gastric pH of stomach with an acid resistant enteric coating
• To improve pharmaceutical elegance by using special colours and contrast printing
• To prevent gastric irritation and instability

5.2.2. Types of Coated Tablets

• Sugar Coated Tablets: Given a sugar coating to mask the objectionable taste and odour
• Film Coated Tablets: Given a thin coating of water-soluble materials which protect the drug substances from atmospheric conditions
• Enteric Coated Tablets: Disintegrate in the intestines and not in the stomach
• Press Coated Tablets: Prepared by compressing granules of incompatible ingredients around a previously compressed tablet

5.2.3. Methods of Tablet Coating

• Sugar Coating: Steps include Sealing/Water Proofing, Sub-Coating, Grossing/Smoothing, Colouring, Polishing, and Printing
• Film Coating: Deposition of a thin film of polymer surrounding the tablet core using spray process
• Enteric Coating: Used to protect the tablet core from disintegration in the acidic environment of the stomach

5.2.4. Merits of Coated Tablets

• They protect the drug from degradation in the acidic environment of the stomach
• They have improved bioavailability and efficacy
• They reduce gastrointestinal side effects like stomach upset
• They can be used to deliver drugs that are sensitive to acidic environments

5.2.5. Demerits of Coated Tablets

• They are generally more expensive than uncoated tablets
• They cannot be crushed before swallowing
• They may delay the release of the drug
• Their coating may impact the efficacy of time-sensitive medications

5.3. UNCOATED TABLETS

Uncoated tablets are those tablets having a single or more than one layer of formulation that consists of active ingredients and excipients compressed together without any additional coat or cover.

5.3.1. Types of Uncoated Tablets

• Oral Tablets: Placed over the tongue and swallowed with water
• Chewable Tablets: Chewed in between the teeth before ingestion
• Sublingual/Buccal Tablets: Placed below the tongue or in the side of the cheek for slow release
• Lozenge Tablets: Dissolve slowly in the mouth to produce a continuous effect on the throat
• Soluble Tablets: Dissolve completely in the liquid to produce solution of definite concentration
• Effervescent Tablets: Contain sodium bicarbonate, citric acid, and tartaric acid which react in water liberating CO₂
• Hypodermic Tablets: Soft, readily soluble tablets used for preparing solutions to be injected
• Vaginal Tablets (Inserts): Used for incorporating antibiotics and steroids
• Implants: Small tablets meant for insertion under the skin for prolonged release

5.3.2. Merits of Uncoated Tablets

• They provide rapid disintegration & drug release
• They are able to exert local effect
• They can be made by wet granulation, double compaction or direct compression
• These drugs are typically water insoluble, e.g., antacid and adsorbents

5.3.3. Demerits of Uncoated Tablets

• They are difficult to swallow as there is nothing to mask the texture or taste
• They are easily destroyed by the gastric pH of the stomach
• They have obnoxious taste and odour
• They have a chalky feel which makes them unpalatable

5.4. VARIOUS MODIFIED TABLETS

Modified tablets are those tablets which are designed to have an intended action as required after administration—to deliver a drug with a delay after its administration or to deliver at a predetermined rate in order to maintain a constant drug concentration for a specific period of time.

5.4.1. Sustained Release Tablets

The drug delivery system that is intended to attain a prolonged therapeutic effect by releasing the medication continuously over an extended period of time once a single dose is administered, is termed as sustained release.

Advantages:

• Minimum drug is used
• It improves the treatment efficacy
• It avoids patient compliance problems
• The drug accumulation with chronic dosing is minimised
• The local, systemic side effects are minimised

Disadvantages:

• Therapy cannot be terminated in case of any side effects
• They are expensive
• Dose dumping occurs if not properly administered
• Increased potential for first-pass clearance
• Poor systemic availability

5.4.2. Extended Release Tablets

Extended-release medications are gradually released into the body over a period of time (12 or 24 hours).

Advantages:

• They are not taken frequently
• They cause fewer side effects
• They cause less fluctuation in blood levels
• They are completely absorbed

Disadvantages:

• They may not be absorbed completely
• They are relatively expensive
• They may cause dose dumping

5.4.3. Fast Dissolving Tablets

Fast dissolving tablets (also called fast-melting, oral disintegrating, or orodisperse tablets) disintegrate and dissolve in the mouth upon contact with saliva, eliminating the need for water.

Advantages:

• Can be easily administered to patients who cannot swallow
• Show patient compliance for disabled, bedridden, and travelling patients
• Can be administered conveniently with accurate dosing
• Produce rapid onset of action

Disadvantages:

• They require careful handling since they lack sufficient mechanical strength
• Improperly formulated tablets may leave an unpleasant taste and/or grittiness

5.4.4. Double Layered Tablets

Bilayer tablets are a primary option for avoiding tabletting chemical incompatibilities between APIs by physical separation, and to allow the development of different drug release profiles.

Advantages:

• Unit dosage forms with maximum dose accuracy
• Non-expensive in comparison to other oral dosage forms
• Lighter and compact, easily swallowed
• Easiest and cheapest in packing and striping
• Can be coated to mask unpleasant odour and bitter taste
• Suitable for large scale production
• Greatest stability among all oral dosage forms

Disadvantages:

• Cannot be easily swallowed by children and unconscious patients
• Amorphous nature and low density character resist compression
• Cannot deliver adequate or full drug bioavailability
• Encapsulation or coating is required for drugs with bitter taste

5.5. OVERVIEW OF TABLET PRODUCTION

5.5.1. Methods of Tablet Production

• Direct Compression: Crystalline substances are directly compressible. Materials should have good flowability, compressibility, be inert, tasteless, able to disintegrate, and economical.
• Wet Granulation: The most widely used process involving wet massing of the powder blend with a granulating liquid, followed by wet sizing and drying.
• Dry Granulation: Powder mixture is compressed without the use of heat and solvent. Methods include pressing (slugging and roller compaction), extruding, tumbling, and fluidising.

5.5.2. Excipients Used in Tablets

5.5.3. Defects in Tablets

• Picking and Sticking: Material adhesion on the punch faces
• Cracking: Small fine cracks on the tablet surface
• Capping and Lamination: Capping—detachment of the tablet top; Lamination—splitting into layers
• Excessive Weight Variation: Due to poor granular flow
• Binding in the Die: Makes tablet ejection difficult
• Mottling: Uneven distribution of colour on tablets
• Variation of Medicament Content: Migration of solute, physical adsorption, or inefficient mixing
• Moisture Sensitivity: May cause instability and affect tablet properties

5.6. EVALUATION OF TABLETS

1. Diameter, Size and Shape

Tablet diameter size and shape depends on the die and punches selected. Tablet thickness should be controlled within a ±5% variation of standard value.

2. Weight Variation

Select 20 tablets randomly, weigh individually, and calculate the average weight. Not more than two tablets should deviate from the average weight by more than the prescribed percentage.

3. Thickness

Tablet thickness can vary without any change in its weight. Thickness is determined with the help of micrometre callipers. The thickness variation limits allowed are ±5% of the size of the tablet.

4. Hardness

• Monsanto Hardness Tester: Small, portable tester using a spring and screw knob. Force is applied until the tablet breaks.
• Pfizer Tablet Hardness Tester: Works on the principle of a plier with a dial.

Hardness of 4kg is considered suitable for handling the tablets. Hardness of 6kg or more will produce tablets of highly compact nature.

5. Friability

Friability test is performed to evaluate the ability of tablets to withstand abrasion in packing, handling, and transporting. The instrument used is the Roche Friabilator. It consists of a plastic chamber that revolves at 25 rpm, dropping tablets from a distance of 6 inches for 100 revolutions.

6. Content Uniformity

Content uniformity test ensures that every tablet contains the stated amount of medicaments within the prescribed limits. Randomly 30 tablets are selected and 10 are assayed individually. The tablet passes if 9 of 10 tablets contain 85–115% of the labelled drug content and the 10th tablet contains 75–125%.

7. Disintegration Test

Disintegration is the first important step involving the breakdown of tablet into smaller particles. The U.S.P. disintegration device uses glass tubes with a 10 mesh screen at the bottom. The tablet must disintegrate and all particles must pass through the screen in the time specified.

Disintegration Time:

• For Uncoated Tablet: 5–30 minutes
• For Coated Tablet: 1–2 hours

8. Dissolution Test

The dissolution rate of a solid drug plays an important role in the absorption and physiological availability of the drug. The apparatus consists of a cylindrical stainless steel basket attached to a stirrer shaft, a 1000ml vessel, and a variable speed motor driven stirrer (25–150 rpm). The dissolution medium is maintained at 37±0.5°C.

Dpharmguru’s exam insights:

Tablet evaluation tests are frequently tested. Remember: Weight variation limits depend on tablet weight. Hardness of 4kg is suitable for handling. Disintegration time for uncoated tablets is 5–30 minutes. Dissolution test measures drug release in the body. These are classic exam questions!

SUMMARY

Tablets are the most widely used dosage form in pharmaceutical manufacturing. This guide covered:

• Definition: Solid unit dosage forms prepared by moulding or compression
• Types: Uncoated, Coated, and Modified tablets
• Coating: Objectives, types (sugar, film, enteric), and methods
• Manufacturing: Direct compression, wet granulation, and dry granulation
• Excipients: Fillers, binders, lubricants, glidants, disintegrants, colouring, flavouring, and sweetening agents
• Defects: Picking, sticking, cracking, capping, lamination, weight variation, binding, mottling
• Evaluation: Weight variation, thickness, hardness, friability, content uniformity, disintegration, and dissolution tests

As I always tell my students: “Tablets are the workhorses of the pharmaceutical industry—mastering their formulation and evaluation is essential for every pharmacist.”

REFERENCES AND FURTHER READING

• Pharmacy Council of India (PCI). (2022). Pharmaceutics Syllabus. New Delhi: PCI.
• Indian Pharmacopoeia Commission (IPC). (2018). Indian Pharmacopoeia (8th ed.). Ghaziabad: IPC.
• Aulton, M. E., & Taylor, K. M. G. (2018). Aulton’s Pharmaceutics: The Design and Manufacture of Medicines (5th ed.). Elsevier.
• Allen, L. V., & Ansel, H. C. (2014). Ansel’s Pharmaceutical Dosage Forms and Drug Delivery Systems (10th ed.). Wolters Kluwer.
• Lachman, L., Lieberman, H. A., & Kanig, J. L. (2018). The Theory and Practice of Industrial Pharmacy (4th ed.). CBS Publishers.
• Subrahmanyam, C. V. S. (2019). A Textbook of Pharmaceutics. Vallabh Prakashan.

Disclaimer: This article is for educational purposes only and does not constitute medical advice. Always consult qualified healthcare professionals for medical concerns. Pharmaceutical regulations and guidelines may vary by region—always refer to your local regulatory authorities for specific requirements.

written by:
Dr. N. Sujith Kumar

Dr. N. Sujith Kumar is a pharmacy educator, Pharm.D graduate, and academic content creator from Jawaharlal Nehru Technological University Kakinada (JNTUK), where he completed his Doctor of Pharmacy (Pharm.D) degree between 2015 and 2021. He has more than 7 years of experience creating pharmacy educational content, writing study materials, and reviewing academic articles for pharmacy students. He has also contributed guest articles to pharmacy education platforms, including PharmD Guru. At D.PharmGuru, his work focuses on simplifying complex Diploma in Pharmacy (D.Pharmacy) subjects into easy-to-understand notes, practical explanations, and exam-oriented educational resources for students across India. His areas of focus include Human Anatomy and Physiology, Pharmaceutics, Pharmacology, Pharmaceutical Chemistry, Hospital and Clinical Pharmacy, and other core D.Pharmacy subjects.

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