Exploring Tablet as a dosage form: Definition, Classification, Preparation Methods & Quality Control test explained Simply
Introduction
A “tablet” refers to a solid dosage form of a pharmaceutical drug. consist of one or more active pharmaceutical ingredients (APIs), which are the substances responsible for the therapeutic effect. In addition to the API, tablets contain excipients—inactive ingredients that help in the formulation, processing, and stabilization of the tablet. Excipients may include binders, fillers, disintegrants, lubricants, and sometimes coloring agents or flavorings.
Advantages and Disadvantages
Advantages of Tablets:
- Easy to handle, store, and transport.
- Accurate dosing with standardized formulations.
- Long shelf life and stability.
- Convenient administration without measuring or mixing.
- Protection of drugs from environmental factors.
- Cost-effective manufacturing processes.
Disadvantages of Tablets:
- Bioavailability is not 100 percent
- Difficulty in swallowing for some individuals.
- Potential delay in the onset of action.
- Limited flexibility in achieving custom dosages.
- Not suitable for all patients.
- Variability in disintegration time may affect absorption.
Classification of Tablets
Based on route of administration:
A. Tablets Ingested Orally
1. Compressed Tablets
2. Enteric Coated Tablets
3. Sugar Coated Tablets
4. Film Coated Tablets
5. Chewable Tablets
B. Tablets Used in the Oral Cavity
1. Buccal Tablets
2. Sublingual Tablets
3. Lozenges Tablets
4. Dental Cones
C. Tablets Administered by Other Routes
1. Implantation Tablets
2. Vaginal Tablets
D. Tablets Used to Prepare Solution
1. Effervescent Tablets
2. Tablet Triturates
Tablet Additives / Excipients / Adjuvants
Tablet additives, excipients, and adjuvants are substances other than the active pharmaceutical ingredient (API) in a tablet formulation. They serve various purposes in the manufacturing and performance of tablets.
Binders:
- Function: To hold the ingredients together and provide cohesiveness.
- Examples: Starch, cellulose derivatives, polyvinylpyrrolidone (PVP)
Diluents:
- Function: To increase the bulk of the tablet, making it a practical size for compression.
- Examples: Lactose, microcrystalline cellulose, calcium phosphate.
Disintegrants:
- Function: To facilitate the breakup of the tablet into smaller particles for better dissolution.
- Examples: Croscarmellose sodium, crospovidone, sodium starch glycolate.
Lubricants:
- Function: To reduce friction during tablet compression and improve the release of the tablet from the mold.
- Examples: Magnesium stearate, stearic acid, talc.
Glidants:
- Function: To improve powder flow properties during manufacturing.
- Examples: Colloidal silicon dioxide, talc.
Colorants:
- Function: To provide color for identification or aesthetic purposes.
- Examples: Iron oxide pigments, titanium dioxide.
Flavorings:
- Function: To mask the taste of the drug or improve palatability.
- Examples: Artificial or natural flavors.
Sweeteners:
- Function: To add sweetness and enhance the taste.
- Examples: Sucrose, sorbitol, mannitol.
Coating Agents:
- Function: To provide a protective layer, control drug release, or mask taste.
- Examples: Cellulose derivatives, shellac, polyethylene glycol.
Antioxidants:
- Function: To prevent oxidation and maintain the stability of the drug.
- Examples: Ascorbic acid, butylated hydroxyanisole (BHA), tocopherols.
Preservatives:
- Function: To prevent microbial growth and extend the shelf life.
- Examples: Parabens, benzoic acid.
Methods of Tablet Preparation
Tablets can be prepared using various methods, each with its own set of advantages and limitations. Some common methods of tablet preparation are:
Direct Compression:
- Process: Active pharmaceutical ingredient (API) and excipients are directly compressed into tablets without the need for granulation.
- Advantages: Simplicity, reduced processing time, cost-effectiveness for certain formulations.
Dry Granulation (Slugging):
- Process: Powders are pre-compressed into large granules (slugs), which are then milled into granules and compressed into tablets.
- Advantages: Minimizes problems associated with powder compression, suitable for moisture-sensitive drugs.
Wet Granulation:
- Process: Powders are mixed with a liquid binder, and the resulting wet mass is dried, milled, and then compressed into tablets.
- Advantages: Improves flow properties, enhances compressibility, allows for uniform distribution of API.
Hot Melt Granulation:
- Process: Binding is achieved by using a meltable binder that is melted and solidifies upon cooling.
- Advantages: Reduces processing time, suitable for moisture-sensitive drugs.
Roller Compaction:
- Process: Powder is compacted between two rollers to form flakes, which are then milled and compressed into tablets.
- Advantages: Efficient for large-scale production, suitable for moisture-sensitive drugs.
Melt Granulation:
- Process: API and excipients are melted together and then solidified to form granules, which are compressed into tablets.
- Advantages: Useful for drugs with poor compressibility, improved stability.
Tablet Coating:
- Process: Already formed tablets are coated with a thin layer of film to improve appearance, taste masking, or control drug release.
- Advantages: Enhanced aesthetics, improved stability, modified drug release.
Effervescent Tablet Preparation:
- Process: Tablets contain a combination of an acid and a base that react to produce carbon dioxide, resulting in effervescence.
- Advantages: Provides a pleasant taste, masks the taste of the drug.
Sublingual and Buccal Tablets:
- Process: Tablets are designed to dissolve under the tongue (sublingual) or against the cheek (buccal) for rapid absorption.
- Advantages: Bypasses the gastrointestinal tract, allowing for quick drug absorption.
Quality Control Tests for Tablets
Quality control tests for tablets are essential to ensure that the manufactured tablets meet the required standards for identity, purity, potency, and performance. Some common quality control tests conducted on tablets are:
1. Shape and Appearance of Tablet:
Method: Visual inspection involves examining tablets under controlled lighting conditions. Any deviations from the specified shape, color, or imprints are noted.
2. Weight Variation:
Method: A sample of tablets is individually weighed using a calibrated balance. The average weight and the percentage deviation from the average are calculated. Results are compared to acceptable limits.
Standard weight variation table:
3. Tablet Thickness:
Method: Tablet thickness is measured using a thickness gauge. Multiple tablets from a sample are measured at different points, and the average thickness is compared to specifications. 5 % deviation may allowed in thickness of tablets
4. Content Uniformity Test:
Method: A sample of tablets is analyzed to determine the uniform distribution of the active ingredient. The results are compared to acceptance criteria.
6. Friability Test:
Method: Tablets are placed in a friability apparatus, and after a specified number of rotations, they are dusted, and the remaining weight is measured. The percentage weight loss is calculated and compared. If loss of weight is less than 1% — Test is passed.
Disintegration Test:
Method: Tablets are placed in individual tubes in a disintegration tester, and the time taken for each tablet to disintegrate is recorded. Results are compared to specified disintegration time limits.
Dissolution Test:
Method: Tablets are immersed in a dissolution apparatus, where they are exposed to a specified dissolution medium and temperature. Samples are withdrawn at various time points, and the concentration of the released drug is measured. The dissolution profile is compared to acceptance criteria.
While tablets are versatile, certain medications may pose formulation challenges, especially those sensitive to moisture or with taste issues.
Tablets undergo various tests, including shape and appearance assessment, weight variation checks, and dissolution tests, to ensure quality and efficacy.
Patients should follow healthcare provider instructions, take tablets with water if required, and report any difficulties in swallowing or adverse reactions.
A tablet is a solid pharmaceutical dosage form containing a compressed or molded mixture of active ingredients and excipients. It is a convenient and widely used method for oral drug administration.