Frequency of administration—Drugs given frequently may need a smaller dose than if administered at longer intervals.  Mode of administration—Injections may require smaller doses than oral medications. Methods of Administering Drugs Drugs may be introduced into the body in several ways, each method serving a specific purpose. ORAL.—Oral administration of medications is the most common method. Among the advantages of administering medication orally (as opposed to other methods) are the following:  Oral medications are convenient.  Oral medications are cheaper.  Oral medications do not have to be pure or sterile.  Awide variety of oral dosage forms is available. Oral medication administration may be disadvantageous for the following reasons:  Some patients may have difficulty swallowing tablets or capsules.  Oral medications are often absorbed too slowly.  Oral medications may be partially or completely destroyed by the digestive system. Other methods of administration closely associated with oral administration are sublingual and buccal. Sublingual drugs are administered by placing the medication under the tongue. The medication is then rapidly absorbed directly into the blood stream. An example of a sublingual drug is nitroglycerin sublingual tablets (for relief of angina pectoris). Buccal drugs are administered by placing the medication between the cheek and gum. Buccal drugs, like sublingual drugs, are quickly absorbed directly into the blood stream. An example of a drug that may be given buccally is the anesthetic benzocaine. PARENTERAL.—Parenteral medications are 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 methods of parenteral administration, including subcutaneous, intradermal, intramuscular, intravenous, and intrathecal or intraspinal. Subcutaneous.—The drug is injected just below the skin’s cutaneous layers. Example: Insulin. Intradermal.—The drug is injected within the dermis layer of the skin. Example: Purified protein derivative (PPD). Intramuscular.—The drug is injected into the muscle. Example: Procaine penicillin G. Intravenous.—The drug is introduced directly into the vein. Example: Intravenous fluids. Intrathecal or Intraspinal.—The drug is introduced into the subarachnoid space of the spinal column. Example: Procaine hydrochloride. INHALATION.—Inhalation is a means of introducing medications through the respiratory system in the form of a gas, vapor, or powder. Inhalation is divided into three major types: vaporization, gas inhalation, and nebulization. Vaporization.—Vaporization is the process by which a drug is changed from a liquid or solid to a gas or vapor by the use of heat (such as in steam inhalation). Gas Inhalation.—Gas inhalation is almost entirely restricted to anesthesia. Nebulization.—Nebulization is the process by which a drug is converted into a fine spray by the use of compressed gas. TOPICAL.—Topical drugs are applied to a surface area of the body. Topically applied drugs serve two purposes:  Local effect: The drug is intended to relieve itching, burning, or other skin conditions without being absorbed into the bloodstream.  Systemic effect: The drug is absorbed through the skin into the bloodstream. Examples of topical preparations are ointments, creams, lotions, and shampoos. RECTAL.—Drugs are administered rectally by inserting them into the rectum. 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. Examples of rectal preparations are suppositories and enemas. VAGINAL.—Drugs are inserted into the vagina to produce a local effect. Examples of vaginal preparations are suppositories, creams, and douches. 6-3