·   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