Drug delivery systems are methods which are used to ensure that drugs get into the body and reach the area where they are needed. These systems must take a number of needs into account, ranging from ease of delivery to effectiveness of the drugs. Several companies specialize in developing methods of drug delivery, marketing these products to pharmaceutical companies, and other pharmaceutical companies develop their own systems. Many of these methods are patented and proprietary.
When a drug is administered, the dosage must be carefully calculated so that the body can use the drug, which requires a drug delivery system which allows for precise dosing. Healthcare professionals also need to consider the way in which a drug is metabolized by the body. For example, some drugs are destroyed in the intestinal tract, which means that they cannot be introduced to the body in this way. Others may be dangerous in large amounts, which means that a time release method should be used to deliver the drug for patient safety.
Topical drug delivery systems involve the introduction of a drug to the surface of the body, in a formulation which can be absorbed. Skin patches are an example of topical drug delivery systems. Other systems involve sprays applied to the mucus membranes of the nose, inhalation aerosols, eye drops, or creams which may be rubbed into the skin. These systems are often very easy for patients to use, which makes them appealing.
Enteral drug delivery systems rely on introducing a drug to the digestive tract, classically through the mouth or rectum. Direct infusion through gastric tubes is another option for getting drugs into the digestive tract. Perenteral systems involve the injection or infusion of a compound into the body. Many vaccines, for example, are delivered through perenteral systems, as are the drugs used in chemotherapy, which are infused into the body for reliable administration. Implants and infusion pumps may be used for drug delivery in patients with chronic conditions.
In all cases, the goal of a drug delivery system is to get the right dosage to the right place. Patients tend to prefer methods which are painless and easy, which is why many pharmaceuticals come in the form of topical and enteral methods which can be taken by mouth or applied directly to the skin. In clinical environments, perenteral routes can be more common, especially for controlled substances, because these methods allow for greater control over how and when the drugs are used.