Tablets are solid dosage forms made by uniformly mixing drugs with suitable excipients and pressing them into flat or irregular-shaped solid preparations. They generally refer to round or other shaped tablets without sugar coating, and can also be made into various types of tablets, such as dispersible tablets, sustained-release tablets, controlled-release tablets, multi-layer tablets, enteric-coated tablets, chewable tablets, and buccal tablets. Capsules, on the other hand, are solid dosage forms filled with drugs or excipients in a hollow capsule or sealed in a soft shell, with an oval shape at both ends, which can contain liquid, gel, or powdered drugs inside.
Tablets are usually round, while capsules are mostly oval-shaped at both ends, and may also differ in size, depending on the drug dosage and formulation requirements. In terms of internal structure, tablets are made by directly pressing drug powder or granules, whereas capsules place the drug inside an edible shell. Additionally, while both can achieve slow drug release, capsules have a relative advantage in timed and targeted drug release. For example, enteric-coated capsules can ensure that the drug is released in the intestines, reducing the stimulation of the drug on the stomach; some special tablets, such as enteric tablets, have similar functions, but the overall structure of capsules provides better protection for such targeted release.
The main process for tablets involves mixing drugs with excipients and then pressing them directly, considering factors such as the compressibility and flowability of the drug to ensure the quality of the tablets. For example, the pressure during the pressing process affects the hardness of the tablets and the disintegration time. The preparation of capsules includes the filling of hard capsules (mixing drugs with excipients uniformly, making them into powders, granules, small tablets, or small pills, and filling them into hollow capsules) or the preparation of soft capsules (sealing a certain amount of liquid drugs directly, or dissolving or dispersing solid drugs in suitable excipients to prepare solutions, suspensions, or emulsions, and then sealing them in soft shells). The quality of the shell is high, such as gelatin as the main raw material for empty capsules, and it is also necessary to consider the use of plasticizers, light blockers, colorants, preservatives, and other additives, and to control the specifications of empty capsules (there are 8 kinds, 000, 00, 0, 1, 2, 3, 4, 5, commonly used 0-5), length, thickness, water content, dissolution time limit, residue after calcination, microbial examination, and other quality indicators.
Masking Unpleasant Drug Odors and Enhancing Stability
The shell of the capsule can effectively encapsulate the drug, providing good protection for drugs with bad smells or those that are easily affected by the external environment (such as air, light, moisture, etc.) and deteriorate. For example, some fish oil capsules have a special fishy smell. If made into tablets, the smell may affect patient compliance due to odor diffusion, while the capsule shell can effectively cover this smell. At the same time, the capsule shell can prevent external moisture and oxygen from entering, protecting the stability of the drug components. Some drugs that are sensitive to oxygen can be better preserved under the protection of the capsule.
Improving Drug Bioavailability and Rapid Efficacy
Drugs in capsules, especially those that are more easily absorbed in liquid or soft states, may have higher bioavailability compared to some tablets. When the capsule enters the body, the shell dissolves quickly, and the drug inside can disperse and dissolve rapidly, thus being absorbed by the human body. For example, some drugs that are insoluble in water can be made into capsules by dissolving the drug in an appropriate oil and filling it into a soft capsule, which can improve the solubility and absorption rate of the drug, and may work faster than tablets.
Timed and Targeted Drug Release
Capsules can achieve timed and targeted drug release. For example, enteric-coated capsules have a specially designed shell that can resist the erosion of gastric acid and will only dissolve and release the drug when it enters the alkaline environment of the intestines. This is very important for drugs that can only better exert their efficacy in the intestines or are irritating to the stomach, such as some antibiotics or enzyme drugs. Making them into enteric-coated capsules can ensure that the drug works in the intestines, avoid damage to the gastric mucosa, and improve the therapeutic effect of the drug.
Solidification of Liquid Drugs
For some drugs that are liquid in nature, capsules can transform them into solid form, which is convenient for storage, transportation, and administration. For example, some drugs containing fats or essential oils of traditional Chinese medicine, when made into soft capsules, not only facilitate patient administration but also ensure accurate drug dosing and improve drug stability.
Accurate Dosing and Stable Quality
During the production process of tablets, precise molds can ensure uniform drug content in each tablet, with accurate dosing. Moreover, since tablets are solid and have a relatively dense structure, they are less affected by external air, light, moisture, etc., especially those with coatings, such as sugar-coated tablets and film-coated tablets. The coating layer can further protect the drug from external environmental interference, making the drug quality more stable and less likely to deteriorate during storage and transportation.
High Production Efficiency and Low Cost
The production process of tablets is relatively mature and suitable for large-scale industrial production. Through mechanized and automated pressing equipment, a large number of tablets can be produced quickly and efficiently. Moreover, since the production process does not require the special shell materials like capsules, the raw material costs and production equipment investment are relatively low. This also makes the price of tablets often cheaper than capsules, which can meet the needs of large-scale medication and have certain advantages in the allocation of medical resources.
Can Be Made into Various Types to Meet Different Needs
Tablets can be made into various types according to different therapeutic needs. For example, dispersible tablets can dissolve quickly in water, suitable for patients with difficulty swallowing or those who need rapid effects; sustained-release tablets and controlled-release tablets can slowly release drugs, maintaining a stable blood drug concentration in the body, reducing the number of doses, and improving patient compliance; chewable tablets are suitable for children or the elderly with poor swallowing function, which can be chewed in the mouth before administration, and the taste is relatively good; buccal tablets are mainly used for local treatment in the oral cavity, such as relieving throat pain.
Limited Range of Applicable Drugs
Not all drugs are suitable for making into capsules. For example, soluble drugs (such as iodides, bromides, etc.), deliquescent drugs, and hygroscopic drugs are not suitable for making into capsules. If soluble drugs are made into capsules, they may dissolve a lot in the shell before the capsule shell is completely dissolved, affecting the normal release and efficacy of the drug; deliquescent drugs lose crystalline water during storage, which may change the properties of the drug and also affect the stability of the capsule shell; hygroscopic drugs easily absorb moisture from the air, which may soften, deform, or even damage the capsule shell, thus affecting the quality and stability of the drug.
High Storage Requirements
The shell of the capsule is prone to mold and softening in high temperature and humidity environments. If the storage environment is improper, such as in places with high humidity or high temperature, the capsule shell may be affected, which in turn affects the quality of the drug. For example, during the plum rain season in the south, if the capsules are not properly stored, they are easy to mold, and such capsules, once taken, may pose a risk to health. Therefore, capsules need to be stored in a dry, cool environment, and attention should be paid to moisture-proof and mildew-proof.
May Be Slower in Efficacy
Compared to capsules, the drug release speed of some tablets may be slower. Especially for ordinary tablets without special designs (such as not being dispersible tablets, rapid-release tablets, etc.), the drug needs to undergo disintegration and dissolution in the body before it can be absorbed, which may take longer than the dissolution and absorption process of capsules. Therefore, in situations where rapid efficacy is needed, tablets may not be as suitable as capsules. For example, in the treatment of acute pain, if ordinary tablets are used, it may take a longer time to feel the effect of the drug, while drugs in capsule form may work faster.
May Irritate the Gastrointestinal Tract
Some tablets, after disintegrating in the stomach, directly contact the gastric mucosa with the drug. For drugs that are irritating to the gastric mucosa, they may cause gastrointestinal discomfort, such as nausea, vomiting, stomach pain, and other symptoms. Although there are special types of tablets like enteric-coated tablets that can reduce gastric irritation, not all tablets have this protective measure. In comparison, capsules (especially enteric-coated capsules) can avoid gastric irritation by releasing the drug in the intestines.
Shape Characteristics
Tablets are generally round or other regular shapes (such as oval, triangular, etc.), and their shapes are relatively regular and flat. Capsules are usually oval-shaped at both ends, looking more like a small ellipsoid, with a certain sense of three-dimensionality. This difference in shape makes them easy to distinguish in appearance. For example, common aspirin tablets are round white tablets, while some fish oil capsules are typical oval capsules.
Size and Weight
In terms of size and weight, there is no fixed rule that capsules are definitely larger or smaller, heavier or lighter than tablets. This depends on specific factors such as drug dosage, the use of excipients, and formulation design requirements. For example, some high-dose drugs may be made into larger tablets or capsules; similarly, to facilitate patient administration, some low-dose drugs may also be made into relatively small tablets or capsules. However, generally speaking, since the capsule shell itself has a certain thickness, the same dose of drug, if made into a capsule, may be slightly larger than a tablet.
State of Drug Components
Tablets mainly press the drug into powder or granule form, and the drug components inside the tablet are relatively dense solid states. The drugs inside the capsule can be powders, granules, or liquids, gels, etc. For example, soft capsules often contain liquid drugs, such as some vitamin E soft capsules, which are liquid vitamin E inside; while hard capsules may contain powdered or small granule drugs, such as some cold capsules, which are a mixture of various powdered drug components inside.
Drug Release Mechanism
The drug release of tablets mainly depends on the disintegration and dissolution process in the body. When the tablet enters the gastrointestinal tract, under the action of digestive juices, the tablet gradually disintegrates into small particles, and then the drug components dissolve from these small particles and are absorbed by the gastrointestinal tract. Different types of tablets will have different disintegration and dissolution speeds, such as dispersible tablets that can dissolve quickly in water, while ordinary tablets require a certain amount of time. The drug release of capsules is first dissolved by the shell, and then the drug (whether it is powder, granules, liquid, or gel) inside quickly disperses and dissolves. For enteric-coated capsules, the shell will not dissolve in the stomach until it enters the specific environment of the intestines and then dissolves and releases the drug. This special release mechanism can achieve targeted drug release.
Complexity of Production Process
The production process of tablets is mainly the mixing and pressing of drugs and excipients. This process is relatively direct, focusing on controlling the uniformity of mixing of drugs and excipients, pressing pressure, tablet thickness, and other parameters. The production process of capsules is relatively more complex. For hard capsules, empty capsules need to be prepared first (including steps such as sol preparation, dipping, drying, shell pulling, cutting, and sorting), and then the powder or granules made by mixing drugs and excipients are filled into empty capsules; for soft capsules, the drug is made into a solution, suspension, or emulsion and then sealed into a soft shell, which involves more processes and technical requirements. For example, the drop-making or pressing process of soft capsules requires precise control.
Differences in Production Costs
Since the production process of tablets is relatively simple and does not require special shell materials like capsules, the production cost is often lower. The production equipment for tablets is relatively common, and a large number of tablets can be produced quickly through efficient pressing equipment during large-scale production, and the cost of excipients for tablets is also relatively low. The production cost of capsules is relatively high, mainly because the production of empty capsules requires certain raw materials (such as gelatin, etc.) and process costs, and the filling or soft capsule production process of capsules also requires specific equipment and technology, which will increase the production cost of capsules.
Ease of Swallowing
For some patients, capsules may be easier to swallow than tablets. The shape of capsules is relatively round and smooth, and they may pass through the throat more smoothly during swallowing. Some larger tablets or irregularly shaped tablets may cause discomfort during swallowing and may even get stuck in the throat. However, some patients may find tablets easier to swallow, which may be related to individual swallowing habits. For example, some elderly or children may find capsules too large to swallow, while adults who are used to swallowing drugs whole may have a higher acceptance of tablets.
Differences in Taste
Tablets usually do not have a special taste, and some tablets may have a bitter or strange taste due to the taste of the drug itself or the taste of the excipients. If there is no coating protection, this taste may be more pronounced. Capsules, due to the wrapping of the shell, basically do not feel the taste of the drug in the mouth until the capsule dissolves in the gastrointestinal tract and releases the taste of the drug, so in terms of taste, they may be better than some uncoated tablets.
For drugs with high stability requirements
If drugs are easily affected by the external environment (such as air, light, moisture, etc.) and deteriorate, capsules often have an advantage. For example, some drugs that are sensitive to oxygen or easily absorb moisture, the shell of the capsule can provide better protection, preventing the drug from contacting the external environment, thus maintaining the stability of the drug. Although tablets can also improve stability through coating and other methods, for drugs with extremely high stability requirements, the protective effect of capsules may be better.
For drugs with poor solubility
For drugs that are difficult to dissolve in water or have poor solubility in specific solvents, capsules may be a better choice. If these drugs are made into capsules, their solubility and bioavailability can be improved by dissolving the drugs in appropriate oils and filling them into soft capsules. For tablets with poor solubility drugs, without special formulation designs (such as making into dispersible tablets, etc.), it may affect the absorption and efficacy of the drug.
When rapid efficacy is needed
When rapid drug efficacy is needed, such as in the treatment of acute pain, acute infections, and other diseases, capsules may be more suitable. Because the drugs in capsules may dissolve and absorb faster in the body, especially those liquid or soft-state drugs in capsules, once the shell dissolves, the drug can quickly disperse and be absorbed. Ordinary tablets may require a longer disintegration and dissolution time, resulting in slower efficacy.
When stable blood drug concentration is needed
In the treatment of some chronic diseases, it is necessary to maintain a stable blood drug concentration. At this time, special types of tablets such as sustained-release tablets or controlled-release tablets have advantages. These tablets can slowly and continuously release drugs, keeping the blood drug concentration in the body at a relatively stable level, reducing the number of doses, and improving patient compliance. Although capsules can also achieve sustained and controlled release through special formulation designs, tablets have more mature and diverse technologies in this regard.
Mass production needs
If there is a need for mass production of drugs, the production process of tablets is more suitable. The production equipment for tablets is relatively simple and efficient, and a large number of products can be produced quickly. Moreover, the cost of tablets is lower, which can meet the needs of mass medication and have certain advantages in the allocation of medical resources. The production process of capsules is relatively complex, and the cost is higher. Mass production may face some challenges in cost control and production efficiency.
Cost-effectiveness considerations
From the perspective of cost-effectiveness, for some common, price-sensitive drugs, tablets are usually a more economical choice. Due to their lower production costs, drug prices can be more affordable, allowing more patients to afford them. Capsules, due to their higher production costs, often have higher prices, which may be limited to some extent for patients with limited budgets or in large-scale public health projects.
Ease of swallowing
For patients with difficulty swallowing (such as the elderly, children, or patients with certain throat diseases), the ease of swallowing capsules and tablets needs to be judged according to specific situations. Although the shape of capsules is relatively round and may be easier to swallow, if the capsules are large or patients have psychological barriers to swallowing capsules, they may find it difficult. For some smaller tablets or specially designed tablets (such as scored for easy breaking), patients may find it easier to swallow. In addition, some patients may be accustomed to chewing or dissolving tablets before administration, which also affects their acceptance of the two dosage forms to a certain extent.
Acceptance of taste and odor
If patients are sensitive to the taste and odor of drugs, capsules may be more popular. Because capsules basically do not release the taste of drugs in the mouth until they dissolve in the gastrointestinal tract. Tablets without coating or incomplete coating may have a bitter or strange taste, affecting the patient’s medication experience. However, for some patients who like to swallow drugs whole and do not mind the taste and odor of drugs, tablets are also acceptable.
Capsules and tablets represent two distinct pharmaceutical dosage forms, each with unique advantages and limitations. Capsules excel in masking unpleasant odors, providing targeted release, and handling liquid medications, while tablets offer precise dosing, cost-effectiveness, and manufacturing versatility. The choice between capsules and tablets depends on specific drug properties, therapeutic requirements, production considerations, and patient preferences, highlighting the importance of tailored pharmaceutical formulation strategies.
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