Frequency of administrationDrugs given
frequently may need a smaller dose than if
administered at longer intervals.
Mode of administrationInjections 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
Awide variety of oral dosage forms is available.
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
Subcutaneous.The drug is injected just below
the skins cutaneous layers. Example: Insulin.
Intradermal.The drug is injected within the
dermis layer of the skin. Example: Purified protein
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
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
TOPICAL.Topical drugs are applied to a
surface area of the body. Topically applied drugs serve
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.