(c) Intrathecal. The intrathecal route involves the administration of a
drug directly into the spine (subarachnoid space) as in spinal anesthesia. The
intrathecal route is used because the blood-brain barrier often precludes or slows the
entrance of drugs into the central nervous system.
(d) Intramuscular (IM). The intramuscular route is used when drugs
are injected deeply into muscle tissue. If the drug is in aqueous (water) solution,
absorption is rapid. However, if the drug is in an oily liquid or in the form of a
suspension, it can prolong the release of the drug.
(e) Intradermal (ID). In this route, the drug is injected into the (top few
layers) of the skin. Ideally, the drug is placed within the dermis. The intradermal route
is used almost exclusively for diagnostic agents.
(f) Subcutaneous (Sub-Q/SC). This route involves the injection of the
drug under the skin into the fatty layer, but not into the muscle. Absorption of the drug
is rapid. Insulin is normally administered subcutaneously.
3-6. TYPES OF ADVERSE REACTIONS TO DRUGS
A patient will sometimes have an adverse reaction to a drug. Adverse reactions
can have a direct toxic effect on various systems of the body or the adverse reactions
can occur in the form of milder side effects.
(1) In general terms, toxicity refers to the poison-like effects certain
substances can produce in the body. Fortunately, most drugs do not produce toxic
effects in most patients. However, when some drugs are administered to a patient over
prolonged periods or when some drugs are given in high dosages, direct toxic effects
can result. Direct toxicity may involve one or more of the body's systems. Certain parts
of the body (that is, bone marrow) produce red and white blood cells. If a toxic
accumulation of a substance affects these parts of the body, blood dyscrasias (the
formation of malformed or destroyed white or red blood cells) may occur.
(2) The liver has as one of its main functions the detoxification of chemical
substances when they are absorbed. If these substances damage the liver significantly,
its ability to detoxify them if greatly affected. Of course, if these substances are not
detoxified, the concentration of the substance in the body (that is, blood stream)
constantly increases. Thus, hepatotoxicity (the destruction of the cells of the liver) can
result in the accumulation of toxic products to the point that other body systems are
(3) The kidneys are responsible for eliminating water-soluble toxic products
(that is, waste products from cellular respiration) from the bloodstream. If nephrotoxicity