8. Mode of administration. This has a definite impact on the dose. Example: Injections may require smaller doses.

METHODS OF ADMINISTERING DRUGS

Drugs are introduced into the body by different routes, each serving a specific purpose.

Oral

Oral administration of medications is the most common method. Advantages are (1) convenience, (2) economy, (3) the drug need not be absolutely pure or sterile, and (4) a wide variety of dosage forms are available. Oral medications include tablets, capsules, liquids, and suspensions. Disadvantages include (1) inability of some patients to swallow, (2) slow absorption, and (3) partial or complete destruction by the digestive system. Other routes associated closely with oral administration are SUBLINGUAL and BUCCAL.

Sublingual—The drug is placed under the tongue and rapidly absorbed directly into the blood stream. Example: Nitroglycerin sublingual tablets

Buccal—The drug is placed between the cheek and gum and is quickly absorbed directly into the blood stream.

Parenteral

Parenteral medications are those introduced by injection. All drugs used by this route must be pure, sterile, pyrogen-free (pyrogens are products of the growth of microorganisms), and in a liquid state. There are several types of parenteral administration.

Subcutaneous—The agent is injected just below the skin’s cutaneous layers. Example: Insulin

Intradermal—The drug is injected within the dermis. Example: Purified protein derivative (PPD)

Intramuscular—The drug is injected into the muscle. Example: Procaine penicillin

Intravenous—The drug is introduced directly into the vein: Example: Intravenous fluids

Intrathecal/intraspinal—The drug is introduced into the subarachnoid space of the spinal column.

Inhalation

Inhalation is the introduction of medications through the respiratory system in the form of a gas, vapor, or powder. Inhalation is divided into three major types:

Vaporization —This is where the drug is changed from a liquid or solid to a gas or vapor by the use of heat, such as steam inhalation.

Gas inhalation—It is almost entirely restricted to anesthesia.

Nebulization—The drug is nebulized into minute droplets by the use of compressed gas.

Topical

Ointments, creams, lotions, and shampoos are examples of topical preparations. Topical application serves two purposes: (1) local effect-the drug is intended to relieve itching, burning, or other skin conditions without being absorbed into the bloodstream and (2) systemic effect—the drug is absorbed through the skin into the bloodstream. Example: Nitroglycerin paste

Rectal

The rectal method is preferred to the oral route when there is danger of vomiting or when the patient is unconscious, uncooperative, or mentally incapable.

Vaginal

Suppositories, creams, or tablets are examples of vaginal preparations which are inserted into the vagina to produce a local effect.

DRUG CLASSIFICATIONS

The definition of a drug is any chemical substance that has an effect on living tissue but