Chapter 6: Drug Interactions Flashcards
drug interactions occur when
a patient takes more than one drug
consequences of drug drug interactions
- intensification of effects (potentiates)
- reduction of effects (inhibits)
- creation of a unique response
intensification of effects
increased therapeutic or adverse effects
reduction of effects
reduced therapeutic or adverse effects
creation of a uniqur response
combined affect does not occur when drugs are used alone; only when used together
drugs interact through what 4 basic principles
- direct chemical or physical interaction
- pharmacokinetic interaction
- pharmacodynamic interaction
- combined toxiciity
drug interaction are most common is
intravenous solution
pharmacokinetic interactions
- altered absorption
- altered distribution
- altered renal excretion
- altered metabolism
- cytochrome P450 group of enzymes
altered absorption
- elevated gastric pH
- laxatives
- drugs and depress peristalsis
- drugs that induce vomiting
- absorbent drugs
- drugs that reduce regional blood flow
altered distribution
- competition for protein binding
- alteration of extracellular pH
altered renal excretion
- filtration
- reabsortion
- active secretion
via changes in blood flow, competition, or changes in pH
which is the most important and complex mechanism in which drugs interact
altered metabolism
intestinal epithelium
affects absorption
placenta
affects drug export from placental cells to maternal blood
blood brain barrier
affects drug export from cells of brain capillaries into the blood
liver
affects drug export from liver into bile
kidney tubules
affects drug export from renal tubular cells into the urine
pharmacodynamic interactions at the same receptor
almost always inhibitory (antagonist /agonist)
pharmacodynamic interactions at separate sites
may be potentitative or inhibitory
how to minimize adverse drug drug interactions
- minimize number of drugs a patient recieves
- take a thorough drug history
- be aware of the possibility of illicit drug use
- adjust dosage when metabolizing inducers are added or deleted
- adjust timing of administration
- monitor patient for early signs of toxicity
- be especially vigilant when a patient is taking a drug with a low therapeutic index
food effect on drug absorption
decreased absortion
the grapefruit juice effect
- inhibits the metabolism of certain drugs
- raises the drugs blood levels
