Therapeutic Drug Monitoring (TDM) Lecture Practice Flashcards

A comprehensive set of practice questions covering the principles of pharmacokinetics, metabolism, sampling guidelines, and specific drug classes used in Therapeutic Drug Monitoring.

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

The measurement of specific drugs at intervals to maintain a relatively constant concentration of the medication in the bloodstream.

What characterizes a drug with a narrow "therapeutic range"?

The effective required quantity is not far removed from the quantity that causes significant side effects and/or signs of toxicity.

What are the five key factors that must be considered in the TDM process?

Route of administration, rate of absorption, distribution of drug within the body, metabolism, and rate of elimination.

Why do orally administered drugs demonstrate more variability in blood levels than IV drugs?

They must pass through the intestine and liver before becoming available in the blood, representing the first major barrier to absorption.

How does pH affect the absorption of drugs across membranes?

Uncharged drugs pass through membranes more readily than charged drugs.

What occurs during Phase I metabolism reactions?

They involve reduction, oxidation, or hydrolysis to make lipophilic drugs more polar.

What defines a Phase II metabolism reaction?

The formation of covalent linkages between a functional group on the parent compound and an endogenously derived group like glucuronic acid, sulfate, glutathione, amino acid, or acetate.

Which specific plasma proteins bind to acidic and basic drugs?

Albumin binds to acidic drugs, while $\alpha_1$-acid glycoprotein binds basic drugs.

What is the definition of drug half-life?

The time necessary for drug concentration to reach $\frac{1}{2}$ of its peak concentration.

What is the formula for the half-life of a first-order reaction?

t_{1/2} = rac{0.693}{K} where $K$ is the constant for a specific drug.

According to the transcript, which three drugs do not follow first-order elimination?

Phenytoin, salicylates, and theophylline.

How many half-lives are typically required for a drug to reach steady state?

5 rac{1}{2} half-lives.

What is the equation for Dosing rate at steady state?

$ext{Dosing rate (mg/min)} = CL imes Css$ where $CL$ is clearance and $Css$ is the concentration at steady state.

What is the difference between pharmacokinetics and pharmacodynamics?

Pharmacokinetics is what the body does to the drug (absorption, distribution, metabolism, elimination), while pharmacodynamics is what the drug does to the body (response, mechanism of action).

Under what condition should free drug levels be measured instead of total drug levels?

When drugs are highly protein bound (>90\% ) and the patient has abnormal protein status, such as albumin < $2.5\,g/dL$, renal failure, or pregnancy.

When should trough level samples be collected?

Immediately prior to the next dose.

What are the recommended collection times for peak levels after oral and IV administration?

1 hour after oral ingestion and $\frac{1}{2}$ hour after completion of IV.

What is the mechanism of action for Digoxin?

It functions by inhibiting membrane $Na^+ - K^+$ ATPase.

What is the primary metabolite of Lidocaine that is additive to the parent drug?

Monoethylglycinexylidide (MEGX).

How are aminoglycoside antibiotics like Gentamicin and Amikacin eliminated?

By renal filtration.

What is the major toxicity associated with high concentrations of Phenytoin (Dilantin)?

The initiation of seizures.

What are the three common methods for determining Lithium levels?

Ion-selective electrode, AA (atomic absorption), or flame photometry.

What is the clinical use of Cyclosporine?

To suppress host-versus-graft rejection of heterotopic transplanted organs like the liver, kidney, or heart.

How does Leucovorin interact with Methotrexate therapy?

Methotrexate inhibits DNA synthesis in all cells; Leucovorin is used to reverse this action to inhibit the destruction of normal cells (Leucovorin rescue).