Chapter 6: Drug Interactions Flashcards
Potentiative interactions
When one drug intensifies the effects of the other.
Inhibitory interactions
When one drug reduces the effects of the other.
4 Basic Mechanisms of Drug-Drug Interactions
1) Direct chemical or physical interaction.
Occur most commonly when drugs are combined in IV solutions.
2) Pharmacokinetic interaction.
When two drugs are taken together, one may alter the absorption, distribution, metabolism, or excretion of the other.
3) Pharmacodynamic interaction.
One drug can alter the effects of another.
4) Combined toxicity.
If drug A and drug B are both toxic to the same organ, then taking them together will cause more injury.
Combining drugs in solutions
Because drugs can interact in solution, never combine two or more drugs in the same container unless you are certain that a direct interaction will not occur.
Inducing agent
When an inducing agent is added to the regimen, it may be necessary to increase the dosages of other drugs. Conversely, when an inducing agent is discontinued, dosages of other drugs may need to be reduced.
Grapefruit juice
Grapefruit juice can inhibit the intestinal metabolism of certain drugs, thereby increasing their absorption, which in turn increases their blood levels.
Drugs that induce PGP
Can cause reduced absorption of other drugs, which would reduce their levels.
Meperidine
morphine derivative for pain relief
Phenergan
antiemetic
potentiative effect
occurs when one drug intensifies the effects of another.
cytochrome P450 (CYP)
When induced it acts on oral contraceptives; therefore, decreasing the effect.
buspirone
remove grapefruit from the patient’s diet
monoamine oxidase inhibitors
Certain cheeses must be restricted
anticoagulants
Spinach must be limited
calcium channel blocker.
consumption of grapefruit should be avoided.
