Empty Capsules: Types, Manufacturing Process, and Packaging Solutions for Pharmaceutical Production

Before discussing capsule materials, manufacturing methods, or packaging equipment, it is helpful to understand what empty capsules actually are and why they are so widely used. From prescription medicines to nutraceuticals and herbal supplements, empty capsules provide pharmaceutical manufacturers with a flexible, accurate, and efficient dosage solution. Their compatibility with automated capsule filling and packaging lines also makes them an essential part of modern pharmaceutical production. Whether you are selecting empty gelatin capsules, evaluating plant-based alternatives, or planning a new capsule packaging line, understanding the fundamentals will help you make better production and purchasing decisions.

What Are Empty Capsules?

In pharmaceutical manufacturing, empty capsules (also called blank capsules or empty pill capsules) are the basic hollow shells used to create oral dosage forms. They act as containers for powders, granules or pellets of medication and supplements. An empty capsule typically consists of two main parts – the cap and the body – which fit and lock together to form a closed shell. (The cap is the shorter top half, and the body is the longer bottom half.) Modern capsule designs include a locking mechanism (such as matching snap-rings or grooves on the cap and body) to ensure the capsule stays tightly closed after filling. This prevents the capsule from accidentally opening during processing, shipping or handling.

In practice, empty capsules serve as a convenient “empty vessel” for medicine. They are commonly made of gelatin or plant-based materials, and are loaded with API or supplements during production. After filling, the cap and body snap together to keep the contents secure. Under a microscope, you can see the capsule cap, capsule body, and often an interlocking ring or double-snap design at the join (as shown below):

• Capsule Cap: The shorter, closed end that fits over the body. It covers the open end of the body once closed.
• Capsule Body: The longer hollow tube with one closed end and one open end. It holds the dose of drug or supplement.
• Locking Mechanism: Many modern capsules have one or two small snap rings or grooves molded on the cap and body. When the capsule is closed, these rings interlock, keeping the cap firmly attached. This prevents cap-body separation caused by internal pressure (e.g. from trapped air during filling) or rough handling. Without a locking feature, capsules could pop open after filling, which would ruin the dose and disrupt production.

In summary, an empty capsule is a ready-to-fill shell consisting of a cap and a body that click or lock together. These hard shells are elastic enough to assemble but rigid enough to survive high-speed filling and packaging lines. They come pre-assembled or as loose caps and bodies (often supplied in bulk trays), and are filled at separate stages in the plant.

Types of Empty Capsules Used in Pharmaceuticals

There are several types of empty capsules, distinguished mainly by their shell material. The most common are:

• Gelatin Capsules: These are the classic hard capsules made from gelatin (animal collagen). They have been used for decades in pharma. Gelatin shells are translucent and have 12–16% moisture content. They are generally inexpensive and dissolve quickly in the stomach. However, gelatin is animal-derived, which may be a concern for vegetarians or certain religious groups. Gelatin capsules are also sensitive to moisture (too dry -> brittle, too humid -> sticky).
• HPMC (Hypromellose) Capsules: Made from hydroxypropyl methylcellulose (a plant-based cellulose), HPMC capsules are vegetarian/vegan-friendly. They typically contain less water (about 4–7% moisture), making them more stable for moisture-sensitive formulations. This also means HPMC shells stay less brittle when stored. HPMC capsules often require a gelling agent (like carrageenan) or hotter dipping than gelatin, but they avoid the use of animal products. They are an excellent choice for customers needing “vegetarian capsules”.
• Pullulan Capsules: Pullulan is a natural polysaccharide (from tapioca) that can form a gelatin-like film. Pullulan capsules are also vegetarian and have very low moisture content, plus a high oxygen barrier (better for protecting sensitive APIs). They are used in nutraceuticals and specialty applications.
• Starch and Other Veggie Capsules: There are also capsules made from modified starch (e.g. hydroxypropyl starch) or other polymers. These are less common but appeal to niche markets (e.g. gluten-free or paleo diets).

Modern pharma has expanded beyond animal gelatin. “As science and technology have advanced, new materials and process improvements have led to the development of empty capsules made of HPMC, hydroxypropyl starch, and pullulan, in addition to gelatin”. In practice, when someone asks for “empty gelatin capsules”, they usually mean hard two-piece capsules of the common material. But capsule suppliers today offer both gelatin and HPMC (vegetarian) capsules in a range of colors and sizes to meet different needs. (When ordering, you may also see them called empty pill capsules, empty medicine capsules, or empty capsule shells.)

Each material has pros and cons. Gelatin is traditional, low-cost and dissolves easily, but not suitable for strict vegetarians. HPMC and other vegan options cost a bit more but suit broader consumer bases. Pullulan has very good moisture protection, which can improve shelf-life of some drugs or supplements.

Empty Capsule Sizes

Empty capsules come in a range of sizes to accommodate different dose volumes. The standard sizes are numbered from 000 (the largest) down to 5 (the smallest). Size 000 is very large – about 1.37 mL internal volume – whereas size 5 is tiny (~0.21 mL). Choosing the right capsule size depends on the fill weight and density of the powder or granules:

• Size 000 and 00 (Largest): These large capsules hold roughly 500–800 mg of a low-density powder. They are often used for bulk supplements or pharmaceuticals requiring large doses (for example, certain veterinary or nutritional formulations).
• Size 0 and 1: These are the most common sizes in human pharma. Size 0 (~500 mg capacity) and size 1 (~400 mg) work well for many medium-strength medications.
• Size 2–5 (Smaller): Capsules sizes 2 (~300 mg) through 5 (~120 mg) are used for potent drugs (when only a small volume is needed) or pediatric formulations. For example, highly potent APIs might be dosed in size 3-5 capsules to keep the pill small.

Table 1 Typical sizes of hard gelatin capsules

The fill volume of each size is typically provided by the capsule manufacturer. For example, a standard chart shows capsule volumes from 1.37 mL (size 000) down to 0.21 mL (size 5). This volume corresponds to a certain weight based on powder density. In fact, Table 2.1 in a pharmaceutical reference lists the volumes and approximate weights for various sizes based on typical tapped densities. When formulating, manufacturers calculate the needed capsule size by the target dose weight and the material’s density (powder tap density).

Applications by size: Nutraceuticals (like multivitamins or herbal supplements) often use larger capsules (0 or 000) because they need to deliver large amounts of herbs or vitamins. Many tablets converted to capsules (over-encapsulation for clinical trials) use standard capsule sizes 1 or 0. Conversely, very small capsules (sizes 3–5) might be used for high-potency drugs, or for easy swallowing by children.

In summary, empty capsules are available in sizes 000 to 5. A general guideline is: the smaller the number, the larger the capsule (i.e. 000 is biggest, 5 is smallest). Manufacturers and capsule suppliers provide size charts so that formulators can pick a capsule that meets the volume requirement of the intended dose. Proper size selection ensures that each capsule holds the correct amount of API for consistent dosing.

How Are Empty Capsules Manufactured?

Empty hard capsule shells (capsule bodies and caps) are produced by a dip-coating process. The basic steps are as follows (see clinical pharmaceutics references for details):

1. Prepare the Dipping Solution: A warm, viscous solution is made by dissolving gelatin (or HPMC) in water at around 60–70°C. Typically this solution is 30–40% polymer by weight. Plasticizers (like glycerol) are added to give the shell flexibility, along with colorants or opacifiers if needed. For HPMC capsules, a gelling agent (like carrageenan or gellan gum) may be included to form a firm film.. The solution is mixed and filtered under strict conditions (GMP) until it has the right viscosity and clarity.
2. Dip-Coat Steel Pins (Molds): Pairs of stainless-steel pin molds are used: one set sized for caps and one for bodies. The pins are arranged on bars and dipped into the warm polymer solution. Since the pins are cooler than the solution, a thin film of gelatin or HPMC sticks to each pin. In one continuous machine, alternating rows of pins form the caps and bodies simultaneously.
3. Rotation and Drainage: After dipping, the bars of pins are lifted out and rotated. This ensures the polymer film is evenly distributed around each pin and excess solution drains off. Rotation and sometimes air knives control the wall thickness of the forming shell. Uniform distribution is critical for consistency in shell strength and dissolution.
4. Drying: The coated pins pass through a controlled drying chamber. Warm (but not too hot) air evaporates water from the film, solidifying it into a rubbery shell. Drying usually takes place under low-humidity, GMP-monitored conditions. The end result is an empty capsule shell (cap or body) on each pin.
5. Stripping and Trimming: Once dry, the capsule shells are stripped (pulled) off the pins. Each shell is then automatically trimmed to the correct length (body and cap lengths are usually different). This step creates the finished “cap” and “body” pieces with open ends that will eventually fit together.
6. Joining Cap and Body: Finally, each trimmed cap is inserted onto a body (a very slight press fit) to temporarily store them as a complete empty capsule. However, they are typically shipped and stored with caps and bodies loosely combined, not locked fully together. (If they were locked too tightly, it would be hard to separate them later during filling.)
7. Printing and Inspection: Optional printing (for logos or codes) can be applied to the joined capsules. Finally, capsules are inspected (often by automated vision systems) for defects (e.g. chips, off-color, wrong size) and then then packed (often in trays or buckets) under controlled humidity (around 40–50% RH) to maintain their moisture content.

All these manufacturing steps are automated and closely controlled for quality. In fact, a published capsule manufacturing guide summarizes these stages: “Step 1: preparation of gelatin solution; Step 2: dip-coating onto metal pins; Step 3: rotation of the coated pins; Step 4: drying of the coated pins; Step 5: stripping and trimming; Step 6: joining of the trimmed capsule shell; Step 7: printing”. (Printing step: After assembly, capsules are often printed with product codes or logos, then inspected and packaged.)

Throughout this process, extensive quality control checks are performed (gelatin bloom strength, viscosity, microbial limits, etc.) to ensure uniform shells. Modern capsule lines can make millions of shells per day, with very consistent weight and dimensions.

How to Choose the Right Empty Capsules

When selecting a capsule type and size, first consider the active ingredient and formulation, then the production method.

Choose by Ingredient/Formulation:

• Moisture-sensitive or hygroscopic APIs: Go with low-moisture shells. HPMC is typically the best choice (HPMC > pullulan > gelatin for moisture barrier). For example, probiotics, enzymes or deliquescent powders should use HPMC or pullulan to minimize moisture uptake.
• Oily or liquid ingredients: Gelatin softgels are standard. For hard shells, HPMC or pullulan are better since they resist oils and provide inert protection.
• High-dose powders or granules: You may need larger capsule sizes (00 or 000) to fit the dose. Gelatin capsules can handle large fills, but large HPMC and pullulan shells are also available.
• Vegetarian/Allergen-free requirements: Use HPMC or pullulan capsules, which contain no animal gelatin. Gelatin is not suitable for strict vegans, vegetarians or certain religious diets.
• Speed of release: If you need very fast disintegration (e.g. a quick-release drug), gelatin is slightly faster than HPMC. If controlled/delayed release is acceptable, HPMC or even enteric-coated capsules might be used.

Choose by Equipment and Scale:

• Small batches / R&D: Manual capsule filling (hand loader or small tabletop machine) is often used for formulation development or low-volume production. It can fill a few hundred capsules per run with a capsule board or simple press.
• Medium production: Semi-automatic capsule fillers (typically 100–400 hole plates) can process thousands of capsules per hour. They combine manual steps with mechanical assistance. They require less operator time than fully manual but have moderate throughput.
• High-volume production: Fully automatic capsule filling machines are used in commercial plants. These machines have large magazine capacities and can fill tens of thousands to hundreds of thousands of capsules per hour. For example, Jinlu Packing’s NJP-7800D automatic filler can handle up to 468,000 capsules per hour (sizes 000–5). Such machines feature high-precision servo control, multi-size cassettes, and GMP design with dust collection. When planning a large production line, integrating an [Automatic Capsule Filling Machine] or complete [Capsule Filling Production Line] (with polishing, inspection and packaging stages) can maximize efficiency.

In summary, pick the capsule material that fits your API (stability, dietary needs) and then choose the capsule size for your dose. Also ensure compatibility with your filling equipment (manual vs. automatic). Modern capsule fillers (like those from Jinlu) are engineered to handle all standard capsule types. For example, tested setups show that gelatin, HPMC and pullulan shells all run smoothly on the same high-speed machines.

Common Applications of Empty Capsules

Empty capsules are used across many industries. Key applications include:

• Pharmaceuticals: Widely used for prescription and OTC oral drugs (painkillers, antibiotics, anti-inflammatories, etc.) where active ingredients are powdered or granular. Gelatin capsules are especially common, but HPMC or pullulan may be used for specialty drugs. Gelita notes that “hard gelatin capsules are ideal for powdered or granulated fillings”, allowing precise dosing of medicines.
• Dietary Supplements: Vitamins, minerals and nutraceutical blends are often encapsulated. Both gelatin and vegetarian capsules are used, depending on consumer preferences. Supplement makers often choose capsule forms for herbal extracts, antioxidant powders, and vitamin complexes.
• Herbal/Natural Products: Many herbal remedies and botanicals are sold in capsule form. The inert capsule shell helps mask taste and protect sensitive phytonutrients. For certain herbs with aldehydes or tannins, producers may prefer HPMC or pullulan to avoid cross-linking issues in gelatin.
• Oils: Oil-based supplements (fish oil, evening primrose oil, etc.) sometimes use modified hard capsules or softgels. Vegetarian oil capsules use HPMC or specially formulated “vegetable softgels.” Empty hard capsules for oils are less common, but HPMC can encapsulate powder forms of oils or oil-containing granules.
• Probiotics: Live-culture products benefit from HPMC or pullulan shells because of their superior moisture protection. Pullulan, in particular, is noted for keeping probiotic bacteria viable much longer by blocking oxygen.
• Veterinary Medicine: Pet and livestock supplements or medications are also produced as capsules. (For example, large size gelatin capsules are used for horse or cattle medicines.) Both gelatin and vegetable capsules are used in vet applications, similar to human pharma.
• Sports Nutrition: Protein blends, creatine, pre-workout and post-workout supplements often come in capsule form (e.g. “pre-workout pills”). Capsule convenience and rapid release are appealing to fitness consumers.

These examples show the versatility of empty capsules. They are a universal dosage form for any powdered or granular product that needs to be swallowed in a precise dose.

How Empty Capsules Are Filled

Filling empty capsules with product can be done in several ways, depending on scale:

• Manual Filling: The simplest method uses a capsule-filling board. You manually separate capsules, fill the bodies with powder (using a spoon or funnel), then join the caps by hand. This is very labor-intensive and suited only to small-scale labs (tens or hundreds of capsules).
• Semi-Automatic Filling: Semi-auto machines (rotary or plate-style) automate part of the process. An operator loads empty capsules into a filling plate (or hopper), the machine aligns and separates cap/body, and the bodies are filled with powder via tamping and spreading. Caps are then placed on top and locked (often by rotating bars). Semi-automatic fillers can produce thousands of capsules per hour with minimal effort.

  

• Automatic Filling: Fully automatic capsule machines are used for large-scale production. They automate feeding (orientation of caps/bodies), powder filling, camming and sealing. Modern machines can handle any hard-shell type. For example, Jinlu’s NJP-3800D is an automatic capsule filling machine that can achieve up to 228,000 capsules/hour. These high-throughput systems often include features like servo-controlled dosing for precise fill weight, multi-size turret chutes, dust extraction, and integration with capsule polisher and inspection equipment. High-speed fillers ensure quick production and consistent dosing.

  

In all filling methods, special care is taken for very light or sticky powders (flow enhancers, lubrication). Dust collection and electrostatic control (ionizers) are important for operator safety and fill accuracy. For large operations, capsule filling machines are a key part of the process chain – they turn the “empty capsules” into finished products at scale.

Capsule Packaging Solutions for Pharmaceutical Manufacturers

Once capsules are filled, the dosage forms must be packaged efficiently. There are a few common packaging solutions for hard capsules:

• Blister Packing Machines: These machines form blisters (aluminum-plastic or aluminum-aluminum pouches), fill each cavity with capsules, then seal and cut the blisters. This is often used for unit-dose packaging of capsules. Modern blister lines can run very quickly – for example, high-speed blister machines can achieve outputs around 10,000 – 11,000 blisters (with capsules) per hour. Jinlu’s DPP-270Max, for instance, is rated at up to 11,200 blisters/hr and handles materials like PVC/Alu film. Blister packaging is popular for keeping individual doses clean, tamper-evident, and moisture-protected. The machines typically include forming, feeding of capsules, sealing, and die-cutting in one line.
• Bottle Filling and Capping Lines: For capsules packed in bottles, the process involves unscrambling bottles, counting and filling capsules into each bottle, adding any desiccant or cotton, capping, and labeling. Capsule counting machines (auto-count fillers) automatically count and dispense precise numbers of capsules. For example, Jinlu’s JL-16C capsule counting filling machine can handle large production of bulk capsules into bottles. These systems ensure each bottle receives the exact count, and they often integrate capping and labeling machines. (The whole line might look like: bottle unscrambler -> capsule counter -> desiccant inserter -> capper -> labeler -> carton/packager.)
• Cartoning and Secondary Packaging: After blisters or bottles are filled and closed, they are typically placed into cartons or cartons are formed automatically around strips. Cartoning machines erect boxes, insert blisters or bottles, and seal them. Finally, case packers bundle multiple cartons for shipping. Jinlu offers cartoning and labeling lines to integrate with blister or bottle lines.

In practice, a pharmaceutical plant may combine these solutions. For example, a high-speed production line might start with an automatic capsule filler, then route capsules to a counting-capping machine, and finally send bottles to a cartoner. Alternatively, for unit doses, the capsules from the filler go to an inline blister machine.

Key point: Packaging equipment should be chosen to match the capsules. Blister machines must handle the size and shape of the capsules (to ensure reliable feeding into the cavities). Counting machines should be compatible with capsule fragility and speed requirements. Many machine vendors (like Jinlu) offer customization: for instance, adjusting feeders or chute guides to suit your capsule size and material. As the manufacturer advertises, their blister packers are built to GMP standards and can pack tablets, capsules, and other forms at high speed.

Ultimately, integrated packaging lines – combining capsule filling, counting, blistering/capping, and cartoning – provide the most efficient solution for large-scale production. They automate the flow from empty capsule to finished packaged product.

Conclusion and Next Steps

Empty capsules (the two-piece shells for pills and supplements) are a foundational element in pharmaceutical production. Understanding their materials, sizes, and design features (like locking mechanisms) helps you choose the right shell for your product. Equally important is knowing the manufacturing and filling process: capsules are made by dip-coating (gelatin/HPMC) and then filled on automated machines that separate, dose, and close each capsule. Finally, proper packaging – via blister machines or counting lines – ensures the filled capsules stay intact and compliant through distribution.

If you’re a pharmaceutical or nutraceutical manufacturer looking for reliable equipment, consider a one-stop solution provider that understands capsules. Companies like Jinlu Packing offer integrated capsule filling and packaging lines that meet cGMP standards. They can help tailor the line to your specific capsule type and output needs. Contact an expert today to discuss how to streamline your capsule production and packaging.

FAQs on Empty Capsules

References：
1.Hard Gelatin Capsules: Formulation & Manufacturing —— studylib.net
2.Locking hard gelatin capsule —— Google Patents
3.HPMC capsules: current status and future prospects —— National Library of Medicine
4.Hard gelatin capsules —— pharmacy180.com
5.A Comprehensive Review On: Capsule —— International Journal of Pharmaceutical Sciences (IJPS)