Taking something orally is the most common method for ingesting substances, from dietary supplements to prescription medications. This route involves introducing a substance through the mouth with the intention of swallowing it. The substance travels down the throat to enter the digestive system, where active components are absorbed into the bloodstream.
The Definition of Oral Administration
Oral administration requires the substance to be swallowed, passing from the mouth, down the esophagus, and into the gastrointestinal (GI) tract. This method is formally known as the enteral route, distinguishing it from all other ways of taking a substance.
This must be differentiated from other methods that use the mouth, such as sublingual or buccal administration. Sublingual substances are placed under the tongue, while buccal substances are held between the cheek and gums. Both absorb directly into the bloodstream through the mouth’s lining, bypassing the GI tract. The oral route is defined by swallowing, which subjects the substance to the stomach’s acidic environment and digestive processes.
Different Forms for Oral Intake
Substances intended for oral intake come in a wide variety of physical forms, each engineered to control how and when the active ingredient is released into the body. Tablets are a widely used form, created by compressing the active ingredient with binders and fillers into a solid dose. Some tablets are coated to protect the drug from stomach acid, ensuring it is not released until it reaches the small intestine.
Capsules are another common form, consisting of a gelatin or polymer shell that contains the medication. These shells dissolve in the stomach or intestines to release the contents, and some are designed as time-release formulations to gradually extend the drug’s effect. Liquid forms, such as syrups and suspensions, are also used, often for people who have difficulty swallowing tablets. Powders or granules provide alternatives that may dissolve faster or be easier to take.
The Journey Through the Digestive System
Once swallowed, the substance begins its journey through the gastrointestinal tract, a process known as pharmacokinetics. For a solid form, the first step is disintegration into fine particles, followed by dissolution into the gastrointestinal fluid. Most oral drugs are absorbed in the small intestine, which has a vast surface area lined with villi, rather than the highly acidic stomach.
Absorption is the next step, where dissolved drug molecules cross the intestinal wall and enter the bloodstream. The blood containing the absorbed drug is first routed via the hepatic portal vein directly to the liver. This initial pass through the liver, known as first-pass metabolism, is where enzymes may chemically break down a portion of the drug before it reaches general circulation. The amount of active drug that successfully reaches systemic circulation is called its bioavailability, explaining why oral doses are often higher than those given by injection. The presence of food can also affect this journey by delaying transit from the stomach or altering how the drug dissolves and is absorbed.