Transcript Drug Interactions

Chapter 25
Drug Interactions
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
Drug Interactions
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A drug interaction can be defined as the
action of an administered drug on either
the effectiveness or the toxicity of another
drug that is administered early,
simultaneously, or later.
Not every potential drug interaction occurs
in all patients.
Not every drug interaction is clinically
significant.
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
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Drug Interactions
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Many dental drug patients take more than
one drug which can increase the risk for a
drug interaction.
Drug interactions may already be
accounted for, and drug doses and timing
are adjusted accordingly.
Over-the-counter drugs can interact with
all other drugs.
A complete medical and drug history can
help to minimize the problems associated
with drug interactions.
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
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Drug Interactions
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Most drug interactions involve an alteration
in the pharmacokinetics of the drug.
Drug Absorption
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Drug interactions can either delay the onset of drug
action or increase or decrease the amount of drug
absorbed.
Rate of drug absorption is a concern when a fast onset
of absorption is necessary.
An example of this would be analgesics. A rapid
response is often desired when the patient is in pain.
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
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Drug Interactions
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Absorption
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Extent of drug absorption is of concern when a drug is
administered over a long period of time.
This is important because it can ultimately affect drug
levels.
Distribution
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Drugs that are highly protein bound can be displaced
from their binding sites.
This small amount of extra drug in the bloodstream can
lead to toxicity.
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
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Drug Interactions
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Metabolism
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Many different drugs can stimulate or inhibit the
metabolism of other drugs.
This can cause an increase or decrease of drug plasma
levels and can lead to toxicity or reduced therapeutic
effect.
Excretion
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Drug interactions that involve excretion can affect the
amount of drug that is either secreted or reabsorbed.
This can lead to an increased effect (toxicity) or
decreased therapeutic effect.
Mosby items and derived items © 2007 by Mosby, Inc., an affiliate of Elsevier Inc.
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Drug Interactions
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Pharmacodynamic drug interactions usually
occur at drug receptor sites.
They can have an antagonistic effect where
no drug effect is seen.
They can have a synergistic effect where two
or more drugs can come together and
enhance a therapeutic or side effect.
They can have an additive effect where both
drugs come together and produce an
expected therapeutic or side effect.
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