Pharmaceutical dosage forms continue to evolve as the industry demands precision, safety, and patient convenience. In Unit 3 of Physical Pharmaceutics, students explore one of the most widely used solid dosage forms—capsules—along with the increasingly popular multiparticulate systems known as pellets. This article presents these concepts in an accessible, news-style educational format designed to enhance understanding and exam readiness.
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Hard Gelatin Capsules – A Classic Dosage Form That Continues to Lead
Introduction to Hard Gelatin Capsules
Hard gelatin capsules remain a staple in pharmaceutical manufacturing because of their simplicity, versatility, and ability to mask unpleasant drug tastes. These capsules are generally composed of gelatin, water, and colorants. Their two-piece structure—a cap and a body—allows effortless filling with powders, granules, pellets, or micro-tablets.
Production of Hard Gelatin Capsule Shells
The production process starts with preparing a heated gelatin solution. Stainless steel mold pins are dipped into this solution to form a uniform thin gelatin layer. After drying, trimming, and recoating steps, the shells are polished and sorted. Automated machinery ensures smooth production and consistency in capsule wall thickness and overall dimensions.
Sizes of Capsules
Hard gelatin capsules are available in standard sizes ranging from 000 (the largest) to 5 (the smallest). The appropriate size is selected depending on the required drug dose, formulation density, and target patient group. Smaller capsules are often preferred for pediatric and geriatric patients.
Filling and Finishing Techniques
Modern capsule filling machines automate all stages—orientation, separation of cap and body, dosing, closing, and polishing. Various filling mechanisms such as auger filling, piston-tamping, and vibratory filling ensure accurate fill weight. After filling, capsules undergo finishing steps that include cleaning, inspection, printing for identification, and packaging.
Manufacturing Defects in Hard Gelatin Capsules
Manufacturing defects, although minimized by automation, may occur due to mechanical or environmental factors. Common defects include deformed capsules, brittle shells, improper locking between cap and body, and fill weight variation. Humidity fluctuations, inadequate drying, or mechanical misalignment are often responsible for such defects.
Quality Control Tests
Quality control plays a crucial role in ensuring capsule safety and efficacy. Important tests include moisture content analysis, dispersibility, appearance check, disintegration and dissolution testing, and fill weight uniformity. These tests verify that final products meet required pharmacopeial standards before release into the market.
Soft Gelatin Capsules – A Modern Solution for Liquid and Semisolid Drugs
Nature of the Soft Gelatin Shell
Soft gelatin capsules differ from hard capsules mainly in their flexible, plasticized shell. Plasticizers such as glycerin or sorbitol allow the shell to accommodate liquid and semisolid formulations. The shell may also contain preservatives, colorants, and opacifiers that improve stability, safety, and appearance.
Capsule Content and Size
Soft gelatin capsules are ideal for oils, suspensions, non-aqueous liquids, and low-melting-point drugs. Depending on dose requirements, these capsules come in a variety of shapes—oval, tube-shaped, or oblong—designed to enhance swallowability and ease of packaging.
Base Adsorption and Minim/Gram Factors
Formulating soft gelatin capsules requires understanding the interaction between the fill material and the capsule shell. Base adsorption affects the final weight of the capsule, and minim/gram factors help determine the volume-to-weight relationship of liquid formulations. These parameters ensure accurate dosing and shell compatibility.
Production of Soft Gelatin Capsules
Softgels are produced mainly through the rotary die process, where two gelatin ribbons are brought together and simultaneously filled and sealed. This method ensures airtight sealing and uniformity in capsule size and fill volume. The process is rapid, efficient, and widely used in both pharmaceutical and nutraceutical industries.
Quality Control, Packing, and Storage
Quality testing includes leakage tests, fill weight uniformity, disintegration tests, and accelerated stability studies. Since soft gelatin capsules are sensitive to moisture and temperature, they require specialized packaging such as blister packs or airtight containers. Proper storage prevents softening, deformation, or microbial growth.
Applications of Soft Gelatin Capsules
Softgels are commonly used for vitamins, essential fatty acids, lipid-based drugs, antioxidants, and hormonal therapies. Their advantages include improved bioavailability, patient compliance, and the ability to encapsulate poorly soluble drugs in solution form.
Pellets – A Rising Star in Multiparticulate Drug Delivery
Introduction to Pellets
Pellets are small, spherical, free-flowing particles typically ranging from 0.5 to 1.5 mm in diameter. Their multiparticulate nature allows better distribution in the gastrointestinal tract, minimizing irritation and ensuring more uniform drug release.
Formulation Requirements
Pellet formulations require an optimal balance of drug, binders, fillers, and coating agents. These ingredients must support good sphericity, hardness, and mechanical strength during processing and handling.
Pelletization Processes
Several pelletization techniques exist, including extrusion–spheronization, hot-melt extrusion, solution layering, and powder layering. The selection of technique depends on drug properties, intended release profile, and equipment availability.
Equipment Used in Pellet Manufacture
Modern pellet production uses specialized equipment such as extruders, spheronizers, fluidized bed processors, and coating pans. These machines ensure consistent pellet size, roundness, and surface smoothness, which are essential for controlled-release formulations.