antagonistic to one another are prescribed together.
Such circumstances seldom occur, but when they do,
the Hospital Corpsman should bring the perceived
incompatibility to the attention of the physician. The
pharmaceutical agents may have been used together
for one agent to modify the activity of the other. The
physician will verify the prescription as necessary.
P H Y S I C A L I N C O M PAT I B I L I T I E S .
Physical incompatibilities are often called pharma-
ceutical incompatibilities and are evidenced by the
failure of the drugs to combine properly. It is virtually
impossible for uniform dosages of medicine to be
given from such solutions or mixtures. Ingredients
such as oil and water (which are physically repellant to
each other) and substances that are insoluble in the
prescribed vehicle are primary examples of physical
incompatibilities.
CHEMICAL INCOMPATIBILITIES.
Chemical incompatibilities occur when prescribed
agents react chemically upon combination to alter the
composition of one or more of the ingredients
(constituents).
MANIFESTATIONS OF INCOMPATIBI ITY.
The following list outlines the various ways
incompatibility between or among drug agents may be
manifested. The respective type of incompatibility is
also noted.
Insolubility of prescribed agent in vehicle
(physical)
Immiscibility of two or more liquids (physical)
Precipitation due to change in menstrum that
results in decreased solubility (called salting
out) (physical)
Liquification of solids mixed in a dry state
(called eutexia) (physical)
Cementation of insoluble ingredients in liquid
mixtures (physical)
Evolution in color (chemical)
Reduction or explosive reaction (called
oxidation) (chemical)
Precipitation due to chemical reaction
(chemical)
Inactivation of sulfa drugs by procaine HCl
(therapeutic)
Although it is, of course, impossible to eliminate
all drug-agent incompatibilities, some combinations
may respond to one of the following corrective
measures.
Addition of an ingredient that does no alter the
therapeutic value (such as the addition of an
ingredient to alter solubility of an agent)
Omission of an agent that has no therapeutic
value or that may be dispensed separately
Change of an ingredient (e.g., substitution of a
soluble form of an ingredient for an equivalent
insoluble form)
Change of a solvent
Utilization of special techniques in com-
pounding
Contraindications
LEARNING OBJECTIVE: Recall drug
contraindications, adverse drug reactions,
and interactions.
A contraindication is any condition the patient
might display that makes a particular treatment or
procedure inadvisable. These conditions include, but
are not limited to, the disease process and other
administered medications.
Adverse Drug Reactions
Adverse drug reactions may occur when a drug,
administered in a dose appropriate for human
prophylaxis, diagnosis, or therapy, has an unintended
and noxious effect on the patient receiving it. As a
Hospital Corpsman, you must be aware of the
possibility of adverse effects of medications so that
you can prevent an occurrence, or at least minimize the
impact on the patient.
Drug Interactions
Patients may receive more than one medication at
a time (as happens frequently in the case of
hospitalized patients). Combining medications can
cause the individual drugs to interact with each
othereither positively or negativelyto produce an
outcome that would not have occurred if each drug had
been administered singly. Such interactions may affect
the intensity of a drugs response, the duration of its
effect, and side effects that may occur.
As stated
above, drug interactions can be positive as well as
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