Pharmacology: Chapter 5

Synergistic Effect

A synergistic effect occurs when two or more "unlike" drugs are used together to produce a combined effect Consider the following example: A beneficial synergistic effect occurs when two different types of antibiotics that work in very different ways are combined, such as penicillin G and an aminoglycoside antibiotic.

Adverse Effect

A usually undesirable effect other than the intended therapeutic effect.

Additive Effect

An additive effect occurs when two or more "like" drugs are combined. An additive effect may be intentional or may unintentionally cause harm.

Antagonistic Effect

An antagonistic drug interaction is the opposite of a synergistic effect. It results in a therapeutic effect that is less than the effect of either drug alone because the second drug either diminishes or cancels the effects of the first drug. Antagonistic interactions can also occur at receptor sites.

Chemical incompatibilities

Chemical incompatibilities between drugs change both the drug's structure and its pharmacologic properties.

When naloxone is given with morphine, it causes what type of drug reaction?

D. Antagonistic effect Antagonistic interactions can also occur at receptor sites. Naloxone is a narcotic antagonist used to correct narcotic overdosage by displacing the morphine molecule off of the receptor site.

Chelation

If a drug binds with another substance in the GI tract, less of the drug is available to be absorbed. This binding of a drug is chelation.

Physical incompatibilities

Physical incompatibilities occur when two drugs are mixed together. The mixture results in the formation of a precipitate.

Potentiated Effect

Potentiation is an interaction in which the effect of only one of the two drugs is increased. In other words, a drug that has a mild effect enhances the effect of a second drug.

Distribution is affected by what two types of drug interactions?

The first is competitive protein binding. The second is drug alteration of the extracellular pH.

The most important and common drug interaction is one that alters...?

The metabolism of a drug. Drugs that induce a hepatic enzyme increase the amount of that enzyme in the liver. If two drugs that affect the cytochrome P-450 system must be administered to a patient together, the dose of one of the drugs may have to be adjusted.

Idiosyncratic response

Unusual and in fact may be the opposite of what is anticipated. Example: If the drug is supposed to make you tired, it makes you wide awake.

Drug Interaction

When two drugs or a drug and another element have an effect on each other. This interaction may: Increase or decrease the therapeutic effect of the drugs. Create a new effect. Increase the incidence of an adverse effect.