A drug delivery system can be broadly defined as any sort of method of delivering a drug intended to have a therapeutic effect; a variety of drug delivery methods are used in both human and veterinary medicine.
The system which is most familiar to the layman is of course an oral delivery system, such as with tablets, capsules and pills of all sorts as well as liquid medications and pastes (pastes are used largely in veterinary rather than in human medicine) intended to be ingested by mouth, also known as a peroral delivery system.
While a capsule or tablet administered by mouth may be the most common form of drug delivery system, there are several others beginning with intravenous drug administration systems. This is commonly used by diabetics to self-administer insulin quickly and in other cases where quick delivery of a drug is necessary or where other types of drug delivery are inefficient or not well suited to the situation.
Immunizations are another common drug delivery situation where injection is considered to be the most effective route; intravenous administration is also preferred where the therapeutic compound is protein-based or contains proteins, since these can easily be destroyed by the digestive system before they can be taken up by the system and have the desired effect.
A transmucosal deliverysystem is used for many medications. Transmucosal drug delivery methods include both tablets and suppositories and may be intended for sublingual, vaginal, rectal, nasal or even ocular use. Administration through the body’s mucous membranes allows very rapid uptake of the drug; often in as little as five minutes time between delivery and therapeutic effect. This is a method of drug delivery which is less common than peroral and some of the other drug delivery methods, with some important exceptions: for example, medicated eyedrops and antihistamines and other medications which are delivered through the nasal mucous membranes via an atomizer.
An increasingly common system is the transdermal method, most often in the form of a patch. These are most familiar to the public in the form of nicotine replacement and birth control patches, though a wide variety of drugs may now be delivered transdermally using much the same mechanism as these better known products. Strictly speaking, however, any sort of medication which is intended for topical use qualifies as having a transdermal delivery system. Ease of use for the patient is the chief advantage of these systems, since a transdermal patch provides a system of drug delivery where the patient can simply apply the patch and leave it alone, something seen by many patients as less onerous than remembering to take peroral medications at regular intervals.
Currently in development are various types of targeted drug delivery system intended to allow the delivery of medication to a tightly focused part of the body. An effective targeted delivery system is something which researchers hope can provide less invasive treatment of many diseases, including certain forms of cancer, since these drugs could be aimed, for instance at a cancerous growth.