Understanding Drug Interactions

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Questions and Answers

What role does a perpetrator drug play in drug interactions?

It increases the therapeutic effect of the object drug.

It enhances the bioavailability of the object drug.

It alters the concentration of another drug. (correct)

It has no effect on the object drug.

Which of the following drugs is noted for having low oral bioavailability?

Metformin

Ibuprofen

Alendronate (correct)

Acetaminophen

Which factor contributes to the increased vulnerability of elderly patients to drug-drug interactions?

Better overall health

Increased age and number of drugs prescribed (correct)

Higher daily water intake

Fewer prescribed medications

What typically occurs in pharmacokinetic drug interactions?

The concentration of a drug in the systemic circulation gets altered. Signup and view all the answers

Which of the following is a potential outcome of harmful drug-drug interactions?

Adverse drug reactions that require hospitalization Signup and view all the answers

What does altered bioavailability refer to?

Changes in drug concentration reaching systemic circulation. Signup and view all the answers

What is a primary concern with diminished oral bioavailability in drugs?

Increased likelihood of drug-drug interactions. Signup and view all the answers

In which phase do behavioral drug interactions occur?

Outside the body Signup and view all the answers

Which drug acts as a strong inhibitor of CYP3A, consequently increasing the risk of myopathy?

Ritonavir Signup and view all the answers

What is the effect of carbamazepine on CYP3A activity?

It induces CYP3A activity. Signup and view all the answers

Which drug inhibits efflux transporters, potentially increasing substrate concentrations?

Verapamil Signup and view all the answers

Which of the following best describes pharmacodynamics?

What the drug does to the body. Signup and view all the answers

Probenecid mainly affects which type of transporters?

Anion transporters Signup and view all the answers

What type of drug interaction is primarily related to changes in drug metabolism?

Enzyme inhibition Signup and view all the answers

Ritonavir-boosted regimens are particularly effective in treating which condition?

HIV Signup and view all the answers

The induction of a cytochrome P450 enzyme typically results in what effect on drug levels?

Decreased drug concentration Signup and view all the answers

What is the primary concern with drugs that are prodrugs?

Their metabolism depends on a single enzyme pathway. Signup and view all the answers

Which of the following best defines bioavailability?

The absorption and initial metabolism of an active drug. Signup and view all the answers

How do pharmacodynamic drug-drug interactions primarily manifest?

Through changed physiological effects. Signup and view all the answers

What is the key factor in determining the clearance of a drug?

The metabolism or excretion of the active drug. Signup and view all the answers

What type of interaction occurs when one drug alters a patient’s behavior?

Behavioral interaction. Signup and view all the answers

Which of the following influences bioavailability by altering absorption?

High fat content meals. Signup and view all the answers

What happens when a perpetrator drug inhibits the conversion of a prodrug?

Reduced effectiveness of the drug treatment. Signup and view all the answers

What can increase the risk of bleeding when co-administering certain medications?

Dabigatran with verapamil. Signup and view all the answers

What type of interactions are particularly common with multiple drugs acting on the central nervous system?

Unintentional harmful interactions Signup and view all the answers

Which of the following is NOT one of the five rules for managing potential drug-drug interactions?

Monitoring the patient's diet constantly. Signup and view all the answers

What is a potential consequence of irrelevant information retrieved during drug interaction alerts?

Alert fatigue among clinicians. Signup and view all the answers

Which drugs are particularly susceptible to pharmacokinetic drug-drug interactions?

Drugs with a narrow therapeutic index Signup and view all the answers

What should clinicians be particularly vigilant about when changing a patient's drugs?

Potential drug interactions Signup and view all the answers

Which reference is commonly used for information about drug interactions?

Micromedex Signup and view all the answers

What aspect of patient physiology contributes to recognizing potential drug interactions?

Pharmacological knowledge Signup and view all the answers

What is likely to improve the chance of recognizing drug-drug interactions?

Improving clinician vigilance Signup and view all the answers

Which of the following drugs is a strong inhibitor of CYP2D6?

Paroxetine Signup and view all the answers

Which enzyme is inhibited by fluconazole?

CYP2C9 Signup and view all the answers

Which of the following is a known inducer of CYP3A?

Rifampicin Signup and view all the answers

What effect does St John's wort have on CYP2C19?

Induction Signup and view all the answers

Which of these options contains two known inhibitors of CYP3A?

Diltiazem and fluvoxamine Signup and view all the answers

Which drug is NOT an inducer of CYP2C9?

Fluconazole Signup and view all the answers

What is the role of grapefruit juice concerning drug interactions?

Inhibitor of CYP3A Signup and view all the answers

Which of the following statements regarding cytochrome P450 interactions is correct?

CYP2C9 can be induced by carbamazepine. Signup and view all the answers

Study Notes

Drug interactions Explained

A drug interaction occurs when the response to a drug is changed by food, supplements, other drugs, or disease.
Drug interactions can be beneficial or harmful.
Harmful drug interactions cause 10-20% of hospitalizations and can be avoided.
Elderly patients are at the highest risk of drug interactions.

Categories of Drug Interactions

Behavioral drug interactions occur when one drug alters the patient's behavior, which influences how they take another drug.
Pharmaceutic drug interactions occur outside the body, usually affecting the formulation of a drug.
Pharmacokinetic drug interactions are when one drug affects the concentration of another drug in the body through changes in bioavailability, clearance, or distribution.
Pharmacodynamic drug interactions are when two drugs affect the body in a way that either adds to or contradicts each other.

Pharmacokinetic Interactions

Altered bioavailability occurs when the amount of drug reaching the system is changed.
Drugs with low oral bioavailability like alendronate and dabigatran, are more susceptible to these interactions.
Altered clearance occurs when the metabolism or excretion of a drug is modified.
CYP450 enzymes are often involved in the metabolism of drugs, and inhibition or induction of these enzymes can lead to altered clearance.
Prodrugs rely on CYP450 enzymes to become active. If the metabolism of the prodrug is altered, it can affect its efficacy.
Some drugs affect the transport of other drugs across cell membranes. This leads to a change in the concentration of the drug at its target.

Pharmacodynamic Drug Interactions

Pharmacodynamics relates to what the drug does to the body.
Pharmacodynamic interactions can be intentional (e.g., when two drugs have a combined effect that is desired), or unintentional and harmful.
Unintentional interactions are common when multiple drugs act on the central nervous system.

Managing Drug Interactions

Five rules can help with managing potential drug interactions:
- Any existing interactions between drugs a patient is taking are already occurring.
- Understanding the pharmacological effects of drugs and patient physiology is essential for recognizing drug interactions.
- Drugs with a narrow therapeutic index face a higher risk of interactions.
- A small number of drugs are common “perpetrators” of drug interactions.
- Drug information services provide access to reference resources like Stockley’s Drug Interactions and Micromedex, which can be used to identify potential drug interactions.

Important Perpetrators of CYP450 Drug Interactions

CYP450 enzyme inhibitors and inducers are important to consider.
Inhibitors slow the metabolism of drugs, potentially increasing their concentration and effectiveness.
Inducers increase the metabolism of drugs, potentially decreasing their concentration and effectiveness.

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Description

This quiz covers the essential concepts of drug interactions, including their definitions, categories, and implications for patient safety. You'll learn about beneficial and harmful interactions, as well as the different types such as pharmacokinetic and pharmacodynamic interactions. Ideal for healthcare students and professionals looking to enhance their knowledge in pharmacology.