Tablet is a most conventional solid oral dosage form containing active ingredient(s) and suitable pharmaceutical excipients. Most of tablets are required to break down (disintegrate) in the stomach or intestine to enable release of drug.
Types of Tablets with Examples
- Immediate Release Tablets (Metronidazole Tablet, Paracetamol Tablet)
- Controlled-release Tablets (Diclofenac SR Tablet, Metformin SR Tablet)
- Enteric Coated Tablets (Rabeprazole Sodium Tablet, Aspirin Tablet)
- Soluble or Dispersible Tablets (Montelukast Tablet, Zinc Sulfate Monohydrate Tablet)
- Buccal and Sublingual Tablets (Propranolol HCl Tablet, Nitroglycerin Tablet)
- Chewable Tablets (Loratadine Tablet, Montelukast Tablet)
- Vaginal Tablets (Miconazole Tablet, Metronidazole Tablet)
Classification of Tablets
Immediate Release Tablets
Immediate-release tablets are developed to dissolve without delaying or prolonging dissolution or absorption of the drug. In this form no deliberate effort is made to modify the drug release rate.
Controlled-release Tablets
A controlled release tablet provides sustained-release characteristics for a specified period of time, whereby the dose is released at a controlled rate as the tablet progresses along the gastrointestinal tract.
Enteric Coated Tablets
If the drug is inactivated at low pH or causes gastric irritation then an enteric coating is applied to ensure that disintegration does not take place in the stomach but readily occurs in the small intestine. Targeting further down the gastric intestinal tract, such as the colon, is also possible. This targeting is usually achieved by coating.
Soluble or Dispersible Tablets
The drug may be formulated as a soluble tablet to be dissolved in water prior to administration. Typically they are formulated with a bicarbonate, for example, sodium or potassium bicarbonate, and with an organic acid, for example, citric acid. The resulting formulation effervesces when added to a tumbler of water.
Buccal and Sublingual Tablets
Buccal tablets are placed in between the tongue and the cheek areas, whereas sublingual tablets are placed under the tongue. The advantage is that they avoid first-pass metabolism, for example glyceryl trinitrate. Alternatively they can be for local action in the mouth, for example, steroids or antiseptics. The tablets should not disintegrate in the mouth. They can be designed to slowly dissolve over 15–30 minutes.
Orally Disintegrating Tablets (ODT)
A solid dosage form containing active substances, which disintegrates rapidly in the mouth, usually within few seconds. It can be administered to the patients having difficulty in swallowing. ODTs show additional clinical benefits such as enhancing oral absorption and bioavailability, improving patient compliance, and for marketing excellence such as extending patent life, product life cycle, and product differentiation.
Chewable Tablets
These tablets are formulated such that they can be readily chewed in the mouth and will also contain sweeteners or flavors if the drug has an unpleasant taste.
Vaginal Tablets
These are designed to be inserted into the vaginal cavity and to release medicament locally. The same design rules apply as for oral tablets. Shape and size of the tablet need to be considered and tensile strength needs to be adequate if an applicator is used.
Oral Lyophilisates
These are solid single dose preparations made by freeze-drying of a liquid or semi-solid preparation. These are intended to be placed in the mouth where their contents are released in saliva and swallowed.
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As per USP, types of tablets are –
- Buccal tablets: Intended to be inserted in the buccal pouch.
- Chewable tablets: Formulated and manufactured to produce a pleasant-tasting residue in the mouth and to facilitate swallowing.
- Effervescent tablets: Upon contact with water, these formulations release carbon dioxide, producing the characteristic effervescent action.
- Hypodermic tablets: Molded tablets made from completely and readily water-soluble ingredients.
- Modified-release tablets: Delayed-release tablets and Extended-release tablets.
- Orally disintegrating tablets: Intended to disintegrate rapidly within the mouth to provide a dispersion before the patient swallows.
- Sublingual tablets: Intended to be inserted beneath the tongue.
- Tablets for oral solution: Intended to be solubilized in a liquid diluent.
- Tablets for oral suspension: Intended to be dispersed in a liquid before administration as a suspension.
- Tablet triturates: Traditionally were used as dispensing tablets in order to provide a convenient, measured quantity of a potent drug substance.
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