Introduction to Tablets & Liquid Orals
Tablets are the most popular solid dosage form, accounting for ~70% of all pharmaceutical preparations manufactured worldwide. This unit covers the complete industrial journey of a tablet — from selecting excipients and granulating powder blends, to compressing them on high-speed rotary presses, coating them for appearance and stability, and rigorously testing their quality. It also covers the formulation and manufacture of Liquid Orals: Syrups, Elixirs, Suspensions, and Emulsions.
Syllabus & Topics
- 1Introduction to Tablets: Most widely used dosage form. Advantages: accurate dosing, easy administration, stability, mass production, patient compliance. Ideal characteristics: elegant appearance, sufficient hardness, disintegrate within specified time, chemically and physically stable.
- 2Classification of Tablets: Compressed tablets (standard), Sugar-coated tablets (SCT), Film-coated tablets (FCT), Enteric-coated tablets (ECT), Sustained-release/Modified-release, Chewable, Effervescent, Buccal, Sublingual, Dispersible tablets.
- 3Tablet Excipients – Diluents/Fillers: Lactose (most common), MCC (Avicel – also binder + disintegrant), Dicalcium phosphate, Starch, Mannitol (for chewable – sweet, cool taste). Added when drug dose is too small to form a tablet of acceptable size.
- 4Tablet Excipients – Binders, Disintegrants, Lubricants: Binders (PVP, starch paste, HPMC – hold granules together). Disintegrants (Crosscarmellose sodium, Crospovidone – swell and break tablet). Lubricants (Mg stearate 0.25-1% – prevent sticking to punches; Talc – glidant for powder flow).
- 5Granulation – Wet Granulation: Most widely used method. Steps: (1) Dry mixing of drug + excipients. (2) Addition of binder solution (granulating fluid). (3) Wet massing. (4) Wet screening. (5) Drying (FBD or tray dryer). (6) Dry screening (sizing). (7) Lubrication. (8) Compression. Produces dense, free-flowing granules with excellent compressibility.
- 6Granulation – Dry Granulation: For moisture-sensitive or heat-sensitive drugs. Methods: Slugging (pre-compression into large slugs → milling) or Roller Compaction (powder compressed between two counter-rotating rollers → ribbons → milling → tableting). No water or heat involved.
- 7Direct Compression: Drug + excipients blended and compressed directly without any granulation. Requires special directly compressible excipients (Spray-dried Lactose, MCC Avicel PH-102). Simplest, fastest, cheapest – but drug must have excellent flow and compressibility.
- 8Compression Equipment: Single-punch press (eccentric – for R&D, small batches). Rotary tablet press (multi-station – high-speed production, 10,000+ tablets/hour). Pre-compression roller + Main compression roller. Tooling: Upper punch, Lower punch, Die (cavity).
- 9Compression Problems & Defects: Capping (top cap separates – air entrapment, excess binder), Lamination (horizontal splitting – similar causes), Picking/Sticking (tablet surface sticks to punch face – moisture, low punch polish), Weight variation (poor flow), Mottling (uneven color distribution).
- 10Tablet Coating – Sugar Coating: Multi-step process in revolving coating pan: (1) Sealing (shellac), (2) Sub-coating (CaCO₃ + syrup), (3) Smoothing (syrup), (4) Coloring, (5) Polishing (beeswax). Elegant appearance, masks bitter taste. Disadvantage: increases tablet weight by 50-100%, time-consuming (days).
- 11Tablet Coating – Film Coating: Thin polymer film (HPMC, Eudragit) sprayed from organic/aqueous solution in a perforated pan or fluidized bed. Faster, increases weight by only 2-5%. More uniform, reproducible. Mostly replaced sugar coating in industry.
- 12Tablet Coating – Enteric Coating: Resists dissolution in gastric acid (pH 1-3) but dissolves in intestinal pH (>5.5). Polymers: Cellulose Acetate Phthalate (CAP), HPMCP, Eudragit L/S. Protects acid-labile drugs (Omeprazole) or prevents gastric irritation (Aspirin).
- 13Quality Control – In-Process Tests: Weight variation (IP limit: ±5% for >250mg), Tablet hardness (Monsanto/Pfizer tester, 4-8 kg), Friability (Roche friabilator, <1% weight loss after 100 revolutions), Thickness, Disintegration time.
Learning Objectives
Frequently Asked Questions (FAQs)
Q1. What Is the Difference Between Wet Granulation and Direct Compression?
Wet granulation involves adding a liquid binder to the powder blend to form moist granules, which are then dried and sized before compression. This method improves powder flow and compressibility but requires additional steps involving heat and moisture. Direct compression eliminates the granulation step; the drug and excipients are simply blended and compressed into tablets. It is faster and more economical but requires powders with good inherent flow and compressibility.
Q2. What Causes Capping in Tablets?
Capping occurs when the top or bottom portion of a tablet separates during or after compression. Common causes include air entrapment during compression, excessive fine particles due to poor granulation, insufficient binder, deep concave punches, and worn or poorly polished tooling. Corrective measures include optimizing granulation, reducing compression speed, increasing binder concentration, and using flat-faced punches.
Q3. What Is Enteric Coating and When Is It Used?
Enteric coating is a protective polymer layer applied to tablets that resists dissolution in the acidic stomach environment (pH 1–3) but dissolves in the more alkaline intestinal environment (pH above 5.5). It is used to protect acid-sensitive drugs such as Erythromycin and Omeprazole, to prevent gastric irritation from drugs like Aspirin and Diclofenac, and to allow drugs like Sulfasalazine to release in the intestine.
Q4. What Is the Friability Test?
Tablet friability is evaluated using the Roche Friabilator to measure resistance to abrasion during handling and packaging. Typically, 20 pre-weighed tablets are rotated at 25 rpm for 4 minutes (100 revolutions). The percentage weight loss is calculated using the formula: Friability = (Initial weight − Final weight) / Initial weight × 100. An acceptable limit is usually less than 1% weight loss.
Q5. What Is the HLB System in Emulsion Formulation?
The Hydrophilic-Lipophilic Balance (HLB) system classifies emulsifying agents on a scale from 1 to 20 based on their affinity for water or oil. Low HLB values (3–6) indicate lipophilic emulsifiers used for water-in-oil emulsions, while high HLB values (8–18) represent hydrophilic emulsifiers used for oil-in-water emulsions. By matching the required HLB of the oil phase with appropriate surfactant blends, formulators can produce stable emulsions.