Classification of Pharmaceutical Tablet:

 1. Based on Method of Preparation:

 

•        Direct Compression Tablets: These tablets are prepared by directly compressing a blend of the active pharmaceutical ingredient (API) and excipients. This method is suitable when the API possesses good flow and compressibility properties. Direct compression tablets are advantageous because they require fewer processing steps and reduce the risk of API degradation due to exposure to heat or moisture during granulation.

•        Wet Granulation Tablets: In this method, API and excipients are mixed to form a granulation mass using a liquid binder. The granules are then dried and compressed into tablets. Wet granulation enhances powder flow, improves compressibility, and promotes content uniformity. However, it involves additional steps and equipment, which can increase production time and costs.

•        Dry Granulation Tablets: Dry granulation involves blending the API and excipients and then compacting them into slugs or ribbons. The slugs or ribbons are then milled and compressed into tablets. This method is chosen when the API is sensitive to moisture or heat, as it avoids the use of water or heat during granulation.

•        Effervescent Tablets: These tablets contain a combination of citric acid and sodium bicarbonate, along with other excipients. When the tablet is dissolved in water, the citric acid and sodium bicarbonate react to release carbon dioxide gas, causing effervescence. Effervescent tablets are often used for antacids, vitamins, and minerals, as they improve palatability and facilitate drug dissolution.

•        Sublingual and Buccal Tablets: These tablets are designed to dissolve quickly when placed under the tongue (sublingual) or against the cheek (buccal). This allows the drug to be absorbed directly into the bloodstream through the rich network of blood vessels in these areas, bypassing the digestive system. Sublingual and buccal tablets are used for drugs that require rapid onset of action.

 

2. Based on Drug Release Mechanism:

 

•        Immediate Release Tablets: These tablets release the entire dose of the drug rapidly upon ingestion. They are suitable for drugs that need to take effect quickly, such as pain relievers or antacids. The drug is absorbed through the gastrointestinal tract, and its effects are felt relatively soon after ingestion.

 

•        Modified Release Tablets:

•        Extended-Release (ER) or Prolonged-Release Tablets: These tablets are designed to release the drug slowly and continuously over an extended period. This reduces the frequency of dosing, maintains steady drug levels, and improves patient compliance. ER tablets often contain special polymers that control the rate of drug release.

•        Delayed-Release Tablets: These tablets have a special enteric coating that prevents dissolution in the stomach's acidic environment. The coating dissolves in the higher pH of the intestines, allowing drug release there. Delayed-release tablets are used to protect acid-sensitive drugs or to target specific absorption sites.

•        Sustained-Release Tablets: These tablets release the drug gradually over an extended period, maintaining therapeutic drug levels in the blood. They can reduce dosing frequency and minimize fluctuations in drug concentration, improving patient outcomes.

 

3. Based on Functionality:

•        Chewable Tablets: Chewable tablets are designed to be chewed before swallowing. They are often flavored to make them more palatable, especially for pediatric or geriatric patients who may have difficulty swallowing traditional tablets.

•        Effervescent Tablets: Effervescent tablets dissolve in water to create a fizzy solution. This can aid in drug delivery by enhancing dissolution and improving the taste of the medication. They are often used for vitamins, minerals, and analgesics.

•        Orally Disintegrating Tablets (ODTs): ODTs disintegrate rapidly in the mouth without the need for water. They are particularly useful for patients who have difficulty swallowing tablets or who need quick relief. The tablet disintegration is achieved using superdisintegrants, which swell and break apart upon contact with saliva.

•        Enteric-Coated Tablets: These tablets have a specialized coating that prevents drug release in the stomach and promotes release in the intestines. Enteric coatings are often used for drugs that are destroyed by stomach acid or that need to be absorbed in the intestines.

 

4. Based on Special Considerations:

 

•        Scored Tablets: Scored tablets have a groove or line on one side, allowing them to be easily divided into halves or quarters. This is useful for dose adjustment or when a specific dosage is needed.

•        Multilayer Tablets: Multilayer tablets contain multiple layers, each containing different drugs or formulations. This allows for the combination of multiple drugs with distinct release profiles or for drugs that interact with each other. Multilayer tablets are useful when multiple medications need to be administered together.

 

5. Based on Route of Administration:

 

•        Oral Tablets: These tablets are ingested through the mouth and are the most common type. They include immediate-release, modified-release, and other types, as discussed earlier.

•        Sublingual and Buccal Tablets: Sublingual tablets are placed under the tongue, where the drug is rapidly absorbed through the sublingual mucosa and enters the bloodstream. Buccal tablets are placed against the cheek, where the drug is absorbed through the buccal mucosa. Both routes offer quick absorption and avoid the first-pass metabolism in the liver.

•        Vaginal Tablets: Vaginal tablets are inserted into the vaginal cavity and are used for local or systemic effects. They can deliver hormones, antimicrobial agents, or other medications to treat gynecological conditions.

•        Rectal Tablets (Suppositories): Rectal suppositories are inserted into the rectum for local or systemic effects. They are often used when oral administration is not feasible, such as in cases of nausea or vomiting.

Each class of tablet serves specific purposes and addresses unique challenges in drug delivery, patient compliance, and therapeutic efficacy. Pharmaceutical manufacturers carefully select the appropriate class of tablet based on the drug's properties, intended use, and patient needs.