Tablets are the most popular and common pharmaceutical dosage forms, which comprises about one third of total medicines prescribed. A tablet is a unit solid dosage form made by compressing one or more ingredients using a tablet press. In rare cases, tablets are made by molding. Nowadays there are different types of tablets available in the market.
Tablets are the first choice in selecting a pharmaceutical dosage form for a patient. We can find a number of advantages for tablets over other dosage forms that makes tablets more popular and patient acceptable.
Read more: what is dosage form
Advantages of tablets
- Stability:
Tablets are a more stable dosage form,they can withstand most of the physical, chemical and mechanical conditions. Also we can increase stability of easily oxidizable or environmentally vulnerable ingredients by providing suitable coating.
- Increased patient acceptance:
- Tablets are lightweight, easy to carry and use
- They are elegant looking and available in different sizes and shapes depending on types of tablets.
- They are easy to swallow using water or other suitable liquids. Coating with materials like gelatin makes it more convenient to swallow.
- Bitter taste or unpleasant smell can be masked by providing appropriate coatings.
- Easy to dispense:
We can make tablets into different colors and shapes and also provide embossed markings and printings. This helps in easily identifying different medicines and reduces confusion to patients.
They are unit solid dosage form with accurate dosing. It helps to provide an accurate and uniform dosage to patients.
Tablets are easy to store and pack. They have a comparatively long shelf life.
- Low manufacturing cost:
Nowadays tablets can be made in bulk quantities with low manufacturing cost. There are different types of tablet machines available which can process even more than one million tablets in an hour.
Even Though tablets are one of the ideal dosage forms for drug administration it also has some disadvantages.
Disadvantages of tablets
- In the case of some patient groups like children, elderly or patients suffering from vomiting or dysphagia tablets are not the suitable dosage form.
- Conditions where patients need a rapid onset of action also tablets are not ideal. Because before getting absorbed to systemic circulation from tablets there are stages like disintegration, dissolution etc. the time needed for these stages are varied depending on the types of tablets.
- Drug absorption from tablets also depends on some physiological factors of the patients like gastric emptying time. This leads to variation in the efficacy of medicines in different patients.
- Drugs which are destroyed by gastric conditions or drugs which irritate gastric mucosa need special enteric coatings, which causes even delay of drug effects.
- Hygroscopic drugs and amorphous and floppy drugs are very difficult to compress to tablet form.
- Oral administration drugs having multiple effects on different organs leads to increased chances of side effects, for example steroids.
How the tablets are made
Tablets are mainly manufactured by compression using a tablet machine. Here active ingredients are weighed accurately and with mixed desired excipients to form a uniform mixture. Different types of excipients are used in the manufacturing of tablets depending on types of tablets. The mixture is then converted into granules. Converting to granules helps improve the flow of ingredients through the tablet machine and prevents segregation and separation of different density powders during the tableting process.
There are two types of granulation methods used,
- Dry granulation method
- Wet granulation method
In the wet granulation method the powders are mixed with a binding agent. After that the mixture is passed through a suitable sieve and dried to convert into granules. These granules are separated and mixed with a glidant. Finally they are compressed to form a tablet using a tablet machine.
In the case of the dry granulation method the powder mixture is first compressed to form lumps using a tablet machine. These lumps are then broken down into granules of proper size. The granules are separated and mixed with glidants. And then passed through the tablet machine to form the final tablet.
In some cases the powder mixture is directly compressed without converting to granule form. This is known as the direct compression method.
Now we can discuss what are the different types of tablets
Types of tablets
Major types of tablets are as follows,
- Uncoated tablets
- Coated tablets
- Enteric coated tablets
- Modified release tablets
- Prolonged release tablets
- Dispersible tablets
- Effervescent tablets
- Lozenges
- Chewable tablets
- Sublingual and buccal tablets
- Mouth dissolving tablets
- Implantable tablets
- Hypodermic tablets
- Uncoated tablets:
These are simple types of tablets. Here medicaments along with other excipients like diluents, binding agents, disintegrants,lubricants etc are compressed to form a tablet of proper shape and size.
Advantages of uncoated tablets include,
- Are cheaper and less time consuming to manufacture.
- They disintegrate faster and release medicines quicker.
Their disadvantages include,
- Bitter unpleasant drugs are difficult to take as an uncoated tablet
- Drugs which are highly reactive to environment conditions are not suitable to make as an uncoated form.
Examples for uncoated tablets are paracetamol 500 mg tablets, cetrizine 10 mg tablets etc.
- Coated tablets
They are of two types
- Sugar coated tablets:
In this case the final compressed tablets are coated with concentrated sugar solution using special techniques.
Sugar coating helps to
- Increase stability of active ingredients
- Mask bitter and unpleasant taste and smell of medicines
- Provides a good appearance and ease of administration
But they have limitations like
- The sugar coating need special techniques and skills and the coating process is time consuming
- Validation of tablets make more difficult
Nowadays sugar coating is not frequently used. Examples for sugar coated tablets include ibuprofen tablets, iron tablets etc.
- Film coated tablets:
Here tablets are sprayed with a polymer solution to form a thin and uniform coating. Nowadays film coating is considered a more popular coating process in tablet manufacturing. Examples of coating polymers are hydroxypropyl methylcellulose, eudragit E 100 etc.
Advantages include,
- Film coating masks unpleasant taste and odor of medicines.
- It provides improved protection against humidity, oxidation and light.
- Film coated tablets are not bulkier compared to sugar coating.
Major disadvantage of film coating is, there are chances of rupture of the coating. Since film coating is very thin, any breakage of the coating will lead to dumping of medicines, which causes drug toxicity.
Film coating also increases disintegration time of tablets.
Examples: diclofenac sodium tablets, erythromycin tablets etc
- Enteric coated tablets
Here tablets are coated with certain polymers which are resistant to gastric pH and soluble in intestinal pH. This type of formulation is also known as delayed release formulations. This technique is used to administer drugs which are destroyed by gastric secretions or drugs which irritate gastric mucosa and produce adverse reactions.
Examples of polymers used for this purpose are cellulose acetate phthalate, hydroxypropyl methylcellulose phthalate etc.
Major disadvantage is that the onset of action from this type of tablet is more delayed.
Examples of formulations include diclofenac delayed release tablets, sulfasalazine enteric coated tablets etc
- Modified release tablets
These types of tablets are made in such a way that they release active drugs in a pre planned manner. In most of the cases these tablets may have an outer layer which releases medicines faster to help attain required plasma concentration of medicine quickly. Remaining medicines are released slowly and in specific time intervals to keep the blood level uniform.
Their advantages are
- Reduce dosing frequency
- Increases patient compliance
- Reduce fluctuation of concentration of medicine in blood
Their disadvantages include,
- Increased price of the tablets
- There is a chance of dose dumping if something wrong happens to the coating materials.
- Prolonged release tablets
These tablets are made by providing a special coating, which releases active drugs in a predetermined manner for prolonged time. They are also known as extended release tablets or sustained release tablets. This technique is mostly used for increasing duration of action for medications having short half lives. Their advantages and disadvantages are similar to that of modified release tablets. Examples include theophylline tablets, lithium tablets etc.
- Dispersible tablets
These tablets are directed to put inside water before administering. There they rapidly disintegrate to form a uniform solution or dispersion of medicine. They may be prepared by adding good flavoring and sweetening agents. This type of formulation helps administration of tablets to children and elderly patients. This also increases the onset of action of medicines.
Examples are piroxicam dispersible tablets, amoxicillin dispersible tablets for children etc.
- Effervescent tablets
These types of tablets when come in contact with water rapidly disintegrated to form a dispersion with releasing carbon dioxide. They are prepared by mixing active ingredients with sodium bicarbonate and organic acids like citric acid or tartaric acid. The release of carbon dioxide helps in reducing the unpleasant taste of medicines.
Examples are vitamin C 1000 mg effervescent tablets and Disprin tablets.
- Lozenges
Lozenges are pleasantly flavored and sweetened tablets intended to be dissolved slowly in the mouth. They are mainly used for relieving coughs and sore throat.they may contain demulcents like zinc gluconate glycine and local anesthetics like benzocaine as active ingredients. Example is strepsils.
- Chewable tablets
These are compressed uncoated tablets intended to be chewed before swallowing. Their advantages include,
- They help administer medicines to children and other patients who have difficulty in swallowing.
- Large amount of drugs can be administered
- Water is not needed for the administration
They have limitations like,
- Bitter and unpleasant medications cannot be made to chewable tablets
- There are a chance of choking if the tablet is swallowed before chewing
Chewable forms of tablets are commonly used for administering antacid preparations. Nowadays a lot of companies make multivitamin tablets for children in the form of chewable tablets.
- Sublingual and buccal tablets
Sublingual tablets are intended to be kept under the tongue, from where the medicines are absorbed directly to the blood circulation. This type of preparation is commonly used for administering nitroglycerin for emergency conditions.
Buccal tablets are another type of tablets, they are usually kept in between teeth and cheek. There it stays for a long time and releases medications. In case of medicines which undergo an increased first pass metabolism these types of tablets are used. This is also helpful in vomiting patients and also in unconscious patients.
Their limitations are that only a small amount of medicines can be administered through this route. Also medicines having bitter taste are not suitable for this formulation.
- Mouth dissolving tablets
These types of tablets when put into the mouth disintegrat or dissolve rapidly within some seconds. They help with easy administration of medicines. example Imodium ( loperamide ) fast melt tablets.
- Implantable tablets
This is one of the controlled drug delivery systems. These are special types of tablets, which release medicaments uniformly for a prolonged time. They are placed subcutaneously by small surgery or using special types of syringes. They are commonly used for the long term administration of hormones like growth hormones or contraceptives. Some tablets release medicines for more than one year.
- Hypodermic tablets
These are sterile rapidly soluble tablets used for the preparation of parenteral solution. These are not commonly used nowadays. Here tablets are mixed with water for injection before administering.
Conclusion
Here we discussed pharmaceutical tablets and different types of tablets. Tablets are the unit solid dosage form made by compression of active drugs with excipients. Most of the tablets are made by compression method. There are different types of tablets available in the market which increase patient acceptance, improves performance of active ingredients and reduces adverse effects and instabilities.
Read more:
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- What is Pharmaceutical mixture
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- What is a Pharmacist
- Pros and cons of being a pharmacist
- What is a Community pharmacy
- Types of adverse drug reactions
- What is ointment and Types of Ointments
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- What are the different sources of drugs
- Natural sources of drugs: Drugs from plants
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