A tablet medicine is a solid oral dosage form created by compressing powdered ingredients into a defined shape, typically round or oblong. This form is the most common way medicines are taken by mouth, offering a convenient and stable method for drug delivery. Tablets are designed to deliver a precise dose of medication to the body, often after being swallowed and traveling through the digestive tract. The durability and ease of manufacture make them a preferred choice for a vast array of over-the-counter and prescription medications.
The Essential Ingredients
Each tablet is composed of two primary categories of ingredients: the active pharmaceutical ingredient (API) and the excipients. The API is the substance that produces the therapeutic effect, such as a pain reliever or an antibiotic. The quantity of the API in each tablet is carefully controlled to ensure the user receives the exact prescribed dosage.
The remaining bulk of the tablet consists of inactive ingredients, which are collectively known as excipients. These substances do not have a direct medicinal effect but are necessary for the manufacturing process and the tablet’s performance in the body. Fillers, or diluents, are common excipients used to increase the overall size of the tablet, making the small quantity of API easier to handle and compress. Lactose or microcrystalline cellulose are frequently used as fillers.
Other excipients serve highly specific functions for the tablet’s structural integrity and breakdown. Binders, such as starch or gelatin, provide the necessary cohesion, ensuring the tablet remains intact during manufacturing, packaging, and handling. Conversely, disintegrants are incorporated to help the tablet break apart quickly once it reaches the moist environment of the gastrointestinal tract. These compounds, often specialized cellulose derivatives, absorb water and swell, causing the tablet to fracture into smaller particles, which is a necessary first step in drug release.
How Tablets Release Medicine in the Body
Once a tablet is swallowed, the medicine delivery process begins in three sequential steps: disintegration, dissolution, and absorption. Disintegration occurs when the tablet breaks down into smaller fragments or granules in the stomach or small intestine, a process facilitated by the disintegrant excipients. This fracture increases the total surface area of the medication available to interact with bodily fluids.
Next, the drug fragments undergo dissolution, where the Active Pharmaceutical Ingredient dissolves into the surrounding liquid in the gastrointestinal tract. The speed of this process depends largely on the drug’s inherent solubility in water. If the drug is not highly water-soluble, dissolution often becomes the slowest step, regulating how quickly the medicine becomes available to the body.
The final step is absorption, which is the movement of the dissolved drug molecules from the digestive tract into the bloodstream. This movement typically occurs through passive diffusion across the intestinal cell membranes. Once the drug is in the bloodstream, it is considered bioavailable, meaning it can travel to its target site to produce the intended therapeutic effect.
Specialized Tablet Types
The design of a tablet can be modified with specialized coatings and formulations to control where and when the medicine is released.
Enteric-coated tablets feature a polymer layer that is designed to withstand the highly acidic environment of the stomach, where the pH is low. This coating prevents the tablet from dissolving until it reaches the small intestine, which has a higher, more alkaline pH. This protects acid-sensitive drugs from degradation and also prevents certain medications, like aspirin, from irritating the stomach lining.
Extended-release or sustained-release tablets are formulated to deliver the medicine over a prolonged period of time. These tablets use a complex internal structure, often a polymer matrix, that controls the rate at which the drug dissolves, preventing it from releasing all at once. This mechanism allows for less frequent dosing, sometimes only once a day, which simplifies a patient’s treatment schedule and maintains a steadier concentration of the drug in the bloodstream.
A third variation includes tablets designed for rapid absorption through the oral mucosa, such as sublingual tablets. These are placed under the tongue, where the medication dissolves and is absorbed directly into the highly vascularized network of blood vessels beneath the tongue. This route bypasses the digestive system and the initial metabolism by the liver, allowing the medicine to reach the systemic circulation quickly for a rapid onset of action, such as with nitroglycerin for chest pain.