Pharmacology Basics Flashcards

When should a trough drug level be collected for therapeutic drug monitoring?

Answer: Immediately before the next scheduled dose

The trough is the lowest concentration, which occurs just before the next dose is given.

Approximately how many half-lives are needed for a drug on a fixed dosing schedule to reach steady state?

Answer: 5 to 7

A drug reaches about 97% of steady state after roughly 5 half-lives.

What is the earliest a digoxin specimen should be collected after an oral dose to get a meaningful level?

Answer: 6 to 8 hours

Digoxin needs about 6-8 hours to distribute into tissue, so earlier samples give falsely high levels.

Gentamicin levels are monitored mainly to prevent which toxic effects?

Answer: Nephrotoxicity and ototoxicity

Aminoglycosides such as gentamicin can damage the kidneys and the inner ear.

Which collection tube must NOT be used for a serum lithium level?

Answer: Lithium heparin tube

Lithium heparin adds lithium to the sample and makes the result falsely high.

A patient with low albumin has a normal total phenytoin level but signs of toxicity. What is the most likely explanation?

Answer: The free (unbound) phenytoin fraction is increased

Phenytoin is highly bound to albumin, so low albumin raises the active free fraction.

First-pass metabolism of an oral drug occurs mainly in the:

Answer: Liver

Oral drugs travel through the portal circulation to the liver, where some is metabolized before it reaches systemic circulation.