Therapeutic Drug Monitoring Overview

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Questions and Answers

What is the primary purpose of Therapeutic Drug Monitoring (TDM)?

To maintain constant serum levels of the drug. (correct)

To increase drug metabolism rates.

To ensure drug absorption is maximized.

To minimize pharmaceutical costs.

Which of the following conditions would most likely require Therapeutic Drug Monitoring?

Significant changes in patient physiology affecting drug levels. (correct)

Drugs with large therapeutic windows.

Drugs that are not metabolized by the liver.

Drugs with high ingestion rates.

Which pharmacological parameter determines the release of a drug?

Liberation (correct)

Absorption

Distribution

Metabolism

Which statement correctly describes the mixed function oxidase (MFO) system?

It is the most significant pathway for drug metabolism. Signup and view all the answers

What bioavailability is associated with intravenous drug administration?

1.0 bioavailable fraction Signup and view all the answers

How does drug distribution affect therapeutic outcomes?

It determines the site of drug interaction with biologic responses. Signup and view all the answers

What is a common relationship observed between drug doses and serum concentrations?

A poor relationship with a good correlation to therapeutic effects. Signup and view all the answers

In pharmacology, what does 'absorption' refer to?

The passage of a drug from its site of administration into systemic circulation. Signup and view all the answers

What is the significance of understanding a drug's half-life in therapy?

It affects the intervals of drug administration. Signup and view all the answers

What role does drug metabolism play in affecting drug efficacy?

It converts prodrugs into active forms. Signup and view all the answers

What is the primary process by which drugs and their metabolites are removed from the body?

Excretion Signup and view all the answers

Which characteristic affects the absorption of drugs in the gastrointestinal tract?

Hydrophobic state of the drug Signup and view all the answers

Which factor is NOT likely to affect the absorption of a drug?

Time spent exercising Signup and view all the answers

Where does the blood from the gastrointestinal tract first route through before entering general circulation?

Liver Signup and view all the answers

What is the term used to describe the relationship between the tissue concentration of a drug and its concentration in the blood?

Distribution space Signup and view all the answers

Which of the following is a cause of drug toxicity?

Elevated levels of free drug Signup and view all the answers

What happens to weak acids in the context of drug absorption?

They are absorbed efficiently in the stomach Signup and view all the answers

Which enzyme system primarily converts parent drugs into their metabolites?

Cytochrome P450 enzymes Signup and view all the answers

What type of drugs are likely to enter the enterohepatic circulation and be excreted in feces?

Lipophilic metabolites Signup and view all the answers

Which condition can change the absorptive characteristics of drugs?

Pregnancy Signup and view all the answers

Study Notes

Therapeutic Drug Monitoring (TDM)

TDM aims to maximize therapeutic benefits while minimizing side effects by maintaining constant serum drug levels.
Most drugs have a half-life unaffected by their concentrations; the half-life is crucial for determining time to reach steady-state concentrations.
Only the free fraction of drug is active, impacting therapeutic response.

Indications for TDM

Serious consequences arise from either overdosing or underdosing.
Small therapeutic window exists, meaning therapeutic and toxic doses are closely related.
Poor correlation between drug dosage and blood concentrations; however, blood concentrations correlate well with therapeutic/toxic effects.
Changes in patients' physiological states can unpredictably alter blood drug concentrations.
Potential drug interactions may necessitate monitoring.
TDM aids in assessing patient compliance with prescribed therapy.

Routes of Drug Administration

The circulatory system efficiently delivers drugs to their target sites.
Intravenous administration guarantees 100% bioavailability (full entry into the bloodstream).
Orally administered drugs typically achieve around 70% bioavailability.

Pharmacological Parameters Determining Serum Drug Concentration

Liberation: Release of the drug from its formulation.
Absorption: Transport of the drug from administration site to bloodstream (LADME).
Distribution: Delivery of the drug to tissues; can result in higher drug concentrations in tissues than in circulation.
Metabolism: Chemical modification of the drug, primarily occurs via cytochrome P450 enzymes in the liver.
Excretion: Elimination of drugs and their metabolites from the body.

Absorption Characteristics

Drugs must be at appropriate concentrations to exert therapeutic effects; passive diffusion is the primary absorption method.
Non-ionized, hydrophobic state enhances absorption.
Drugs absorbed from the intestine enter the hepatic portal system and pass through the liver before entering general circulation.
Liquid solutions absorb quickly; tablets and capsules require dissolution first.
Weak acids absorb mainly in the stomach, while weak bases absorb primarily in the intestine.
Absorption influenced by factors like intestinal motility, pH, inflammation, and concurrent food or medication intake.

Distribution of Drugs

Effective drug concentrations generally occur in body tissues, not in blood.
Drugs often reach higher tissue concentrations compared to blood, indicating a large distribution space.
A large distribution space suggests significant movement of the drug into tissues from circulation.

Excretion of Drugs

Drug clearance rates depend on drug type and patient metabolism/excretion capabilities.
Drugs are excreted either unchanged or as metabolites; liver metabolizes parent drugs via cytochrome P450 enzymes.
Some drugs are recirculated into the enterohepatic system and can be excreted in stool.

Causes of Drug Toxicity

Elevated free drug concentration can lead to toxicity.
Abnormal responses to drugs post-administration can signify toxicity.
Active drug metabolites may contribute to adverse effects.

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Description

This quiz covers the fundamentals of Therapeutic Drug Monitoring (TDM), focusing on its importance in maximizing therapeutic benefits while minimizing side effects. It highlights key concepts such as drug half-lives, indications for TDM, and the implications of drug administration routes on patient care.