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Pharm Ch 6

Terms in this set (23)

How many drugs at minimum are involved in drug-drug interactions?
minimum two drugs
3 possible consequences of drug-drug interactions?
potentiation
inhibition
idiosyncratic
potentiation
intensification of therapeutic or adverse effects (ex: warfarin and asa)
inhibition
reduced therapeutic or adverse effects
ex: narcan
idosyncratic response
unique response
very unlikely to happen
Altered Absorption example due to drug interaction
A laxative reduces time for another drug to be absorbed through intestine
Altered Distribution example due to drug interaction
two drugs that competitively bind to albumin
Altered Metabolism
drugs can inhibit or induce CYP enzymes OR compete for same enzymes
Inducers
Drugs that induce CYP enzymes
result: drugs metabolism faster with less of therapeutic effect
Inhibitors
Drugs that inhibit CYP
Result: Drug metabolized slower leading to toxicity
Altered Excretion
BP lowering drug could reduce GFR thereby decreasing excretion of another drug
Interactions at the same receptor
two drugs compete for the same receptor, usually inhibitory
ex: narcan to reverse OD
Interactions at different receptor sites
two drugs may influence the same physiologic process but at different receptors
potentiative or inhibitory
ex: morphine and diazepam both CNS depressors
Precipitate
some drugs undergo direct chemical interactions and form a solid
common with IV
Combined Toxicity
two drugs can have similar toxic effects on a tissue or organ, try not to use them together
ex: isoniazid & rifampim to treat TB
both are hepatotoxic
polypharmacy
more drugs one takes = greater risk of interactions
Who is usually taking multiple medications?
the elderly
With what kind of TI are interactions very important to keep in mind?
drugs that have a small TI
What two steps of pharmacokinetics can be affected by a drug-food interaction? What does it do?
can increase or decrease ABSORPTION OR METABOLISM
What does grapefruit juice do to CYP3A4? What happens to drug levels?
can inhibit enzyme
drugs levels rise --> toxicity
Where are CYP3A4 enzymes found in the GI tract?
liver and intestinal wall
Drug-Food Interaction increasing toxicity example
K-sparing diuretics and salt substitute
Lots of POTASSIUM --> toxicity
Drug-Food Interaction affecting drug action example
Vitamin K and Warfarin
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