drug interactions and adr's Flashcards
(81 cards)
What is a drug interaction?
When one drug alters the effects of another drug.
How can Drug A affect Drug B?
Increased or reduced effect
Slower or more rapid effect
New or increased side effects
What is a precipitant drug?
The drug that causes the interaction.
What is an object drug?
The drug whose effect is altered.
What is the FDA definition of a serious adverse event?
Death
Life-threatening
Hospitalization (initial or prolonged)
Disability (significant, persistent, or permanent)
Congenital anomaly
Requiring intervention to prevent permanent impairment.
How can interactions and adverse reactions be prevented?
Avoid drugs that interact.
Adjust the dose of the object drug.
Change dosing intervals to avoid interactions.
Monitor for early detection.
Provide information on risk factors.
Improve computerized screening systems.
Focus on clinically significant interactions.
Pharmacokinetic interaction
Alters the amount of drug available in circulation.
Most common type of interaction.
Pharmacodynamic interaction
The drug’s effect is altered, but amount of drug in circulation remains the same.
Less common type of interaction.
What are absorption-based drug interactions?
One drug make the absorption of another drug … Faster or slower, Less or more complete
What are the mechanisms that affect drug absorption?
Direct alterations of absorption
Ionization changes (pH alterations)
Changes in gastric emptying and GI motility
Chemical interaction (chelation)
Where are most orally delivered drugs absorbed?
small intestines
How does reduced gut motility affect drug absorption?
increases absorption because the drug spends more time in the small intestine
How does increased gut motility affect drug absorption?
reduces absorption because the drug moves through the intestines more quickly, leading to less time for absorption
How does H-2 blockers (e.g., Zantac) affect ketoconazole absorption?
decrease the dissolution of ketoconazole, resulting in reduced absorption
What is an example of a drug interaction involving gastric pH alteration?
H-2 blockers (e.g., Zantac) + ketoconazole
How do antacids affect drug absorption?
decrease the absorption of acid drugs (e.g., aspirin, anticoagulants) by changing the percent of drug that is ionized
What does pKa represent in drug ionization?
pKa is the pH at which a drug is 50% ionized and 50% unionized.
T or F: The ionization of acid and basic drugs depends on the pH of the environment.
True
How does altered gastric emptying affect drug absorption?
If Drug A alters the rate of gastric emptying, the rate of absorption of Drug B is also altered.
What happens when absorption rate is slower?
Peaks become lower
Peaks are shifted to the right
What is complexation/chelation in drug absorption?
Two drugs bind together in the GI tract
Neither drug is absorbed
What causes interactions from changes in drug distribution?
Displacement of bound drug from blood plasma proteins
T or F: One drug can alter the rate at which a second drug is inactivated or degraded
True
How does one drug affect another in drug distribution?
One drug can displace another from plasma proteins, increasing the free drug concentration