causes a tolerance to another drug. Alcoholics, barbiturate addicts, and narcotic
addicts develop a cross-tolerance to sedatives and anesthetics.
i. Time of Administration. The time when a drug is administered is important.
Some orally administered medications should be taken before meals (that is, on an
empty stomach) to increase the amount of drug absorbed into the system. Other oral
medications (that is, those that cause irritation to the gastrointestinal tract) should be
taken after meals on a full stomach.
The interaction between two or more drugs may influence the overall
effectiveness of each of the drugs.
(1) Synergism. Synergism is the joint action of drugs. That is, their
combined effects are greater than the sum of their independent effects. Concurrent
administration (giving both drugs at the same time) of synergists may require that the
dose of each drug be lowered. In the case of synergism, 1 + 1 = 2 1/2. Synergism may
be beneficial or harmful. Beneficial effects may be obtained when combining two
potentially toxic drugs to achieve the desired therapeutic effect without causing harm to
the patient. Harmful effects may occur when alcohol and some depressants are
(2) Additive. In an additive drug interaction, the combined effects are equal
to the sum of the independent effects of the drugs. In the case of the additive effect,
1 + 1 = 2.
(3) Antagonism. Antagonism is the canceling effect of one drug upon
another. A sedative administered with a stimulant may antagonize or cancel the effects
of the stimulant. Of course, the degree of antagonism varies from complete cancellation
of the effect to varying degrees of reduced effectiveness.
k. Routes of Administration. Drugs may be given to patients using a variety of
methods. Some drugs are only effective if they are given in a particular dosage form.
Other drugs are administered in forms that enhance or decrease their effect or localize
the drug effects.
(1) Oral. Most drugs available today can be administered by mouth (orally).
Drugs can be orally administered in the form of tablets, capsules, powders, solutions, or
suspensions. Drugs administered by the oral route are usually taken for their systemic
effect. These medications must pass through the stomach and be absorbed in the
intestinal tract. Orally administered medications are usually easy to take and are
usually less expensive than other dosage forms.
(2) Sublingual/buccal. The sublingual/buccal route of administration is
closely related to the oral route; however, in the sublingual/buccal route the dosage