Flashcards in Pharmacokinetics Deck (25):
volume of distribution =
amount of drug in body/plasma drug concentration
low Vd means drug distributes to:
medium Vd means drug distributes to:
high Vd means drug distributes to:
all tissues (including fat)
- volume of plasma cleared of drug per unit time
- (0.7)(Vd)/(t 1/2)
fraction of administered drug reaching systemic circulation unchanged
How many half lives does it take for a drug to reach steady state?
4-5 (time to steady state depends ONLY on t 1/2 of the drug)
In renal or liver disease, the ______ dose remains unchanged but the ____ dose decreases.
- rate of elimination is constant regardless of drug concentration
- constant amount of drug eliminated per unit time
Key examples of zero-order eliminated drugs:
phenytoin, ethanol, aspirin (PEA in shape of 0!)
- rate of elimination is proportion to drug concentration
- constant fraction of drug eliminated per unit time
Only ____ forms of drug can be reabosorbed.
Weak acids get trapped in ____ environments.
Weak bases get trapped in ____ environments.
pH > pKa
pH < pKa
Phase I metabolism
- reduction, oxidation, hydrolysis via CYP450
- yields slightly polar, water-soluble metabolites that are often still active
Phase II metabolism
- conjugation (glucoronidation, acetylation, sulfation)
- yields polar, inactive metabolites
- preserved in geriatrics
maximal effect a drug can produce (Vmax)
amount of drug needed for given effect (more potent = less of it needed) (Km)
competitive antagonists change ____ but not ____.
noncompetitive antagonists change ___ but not ____.
partial agonists change ____ and changes in ____ are variable depending on mechanism
TD50/ED50 --> want it to be VERY large to be a safe drug