Drugs and medications inherently possess diverse pharamcologic characteristics, thus requiring various methods of delivery into the body. Parameters such as pKa, convenience, bioavailability, and metabolic effects are some considerations. Some drugs, for example, can tolerate the acidic environment of the stomach, and may thus be taken orally. Others are more effective when administered into the bloodstream or inhaled into the lungs.

* Oral medications are taken through the mouth. This is the most common and convenient way of delivering drugs into the system. Depending on how the drugs interact with the stomach acids and the time needed to pass through the gastrointestinal system, drugs may be recommended to be taken with or without food.
* Intravenous (IV) medication is injected into a blood vessel, typically a vein, for direct entry into circulation.
* Intramuscular medication is added via injection into muscle.
* Medication that is delivered subcutaneously is injected directly under the outer layers of skin. Some local anesthetics use this form of drug delivery.
* Sublingual medication is placed under the tongue. The drugs can be absorbed into the blood vessels in the region and can enter general circulation before passing through the liver.
* Rectal medication is introduced through the anus.
* Medication delivered via inhalation may be in a liquid mist or gaseous form. Bronchodilators for asthma and some experimental flu vaccines use this form of administration.
* Topical medications are applied onto the skin surface. Many dermatologic ointments commonly use this form of administration.