Pharmacology Flashcards
Vd: Definition and physiological significance
Volume of distribution
Measurement of how much of a drug is distributed into organs/tissues rather than remaining in systemic circulation
Who is the first line of defense against a pt getting on the wrong medication?
prescribers
What is pharmacokinetics?
how the body impacts the drug–> absorbed, distributed, eliminated
What is a standard drug dose?
based on trials in “healthy” individuals with “average” physiologic processes
In what form is a drug able to go to and have an effect on target receptors?
free form/ not bound
If needed how do drugs, which are usually large and polar, get through the cell membrane?
protein pores/channels, facilitated/active carriers, some can move through based on diffusion
uncharged molecules are readily…
lipid-soluble
charged molecules are readily…
water-soluble
pKa
charged
pKa>pH (drug form)
uncharged
Alkaline urine favors the excretion of…
weak acids
Acidic urine favors the excretion of…
weak bases
Drugs designed to act on the CNS must be…
hydrophobic
intrathecal administration
drug is directly injected into the CSF/ bypasses the BBB
What are four ways drugs can be taken up?
enteral, parenteral, transdermal, and mucous membranes
First-pass metabolism occurs where and affects what drugs?
in the liver, oral drugs only
What is first-pass metabolism?
drugs are carried from GI to the liver via the hepatic portal vein and since the liver is a major site of metabolism, the liver may modify drugs rendering them inactive or reduce how much is actually sent to the target tissue (sometimes the opposite will occur and the drug will activate)
Bioavailability
(drug reach systemic circulation/drug administered)
the fraction of uncharged drug reaching the system circulation
between 0-100
Bioequivalence
compares the bioavailability of a generic drug to the brand name–> should have the same amount of active ingredient and the same predictable response
What is a loading dose?
initial doses of a drug that is administered to compensate for distribution into the body tissues; gets the pt to steady state quicker
What is loading dose dependent on?
volume of distribution
If Vd is high then plasma drug concentration is…
low; the drug will be extensively distributed to the tissues(muscle, adipose, and other non-vascular compartments)–> has a LONG duration of action
What is the steady state?
therapeutic dosing of a drug maintained during peaks(high [drug]) and lows(low [drug])– usually takes between 3-5 half-lives to achieve
What is a maintenance dose?
subsequent doses used to replace the amount of drug lost through metabolism/excretion/ goal is to maintain a steady state concentration
What is a maintenance dose dependent on?
clearance = (metabolism+excretion)/[drug]plasma
Tight junctions restrict drug distribution into the sanctuary compartments. What are these?
the blood-brain barrier in the CNS and the blood-testes barrier in the testes
Where in the body are you likely to find water-soluble drugs?
blood
Where in the body are you likely to find fat-soluble drugs?
cell membranes, adipose, and other fat-rich areas
Vd (equation)
= amount of drug in body/ plasma drug [ ]
remember it can exceed body volume
Example of a drug with a low Vd
heparin (mostly found in the vascular compartment)
Vd of 42L example
alcohol
Examples of high Vd (over 42L)
chloroquine, azithromycin, digoxin
Rate of accumulation into tissue compartments depends on?
blood flow, the chemistry of the drug, and plasma protein binding of the drug
What are the three binding proteins?
albumin (acidic binding), alpha 1 acid glycoprotein (basic drug binding), and lipoprotein (lipophilic drug binding)
Only _____ drugs can act at target sites and elicit biological responses
free, unbound
A disease state of drug can displace a highly bound protein drug and _____ the free drug state. Two examples are
hypoalbuminemia and ceftriaxone(exacerbate the hyperbilirubinemia)
Monitor a _____ clearance drug with a low therapeutic window when coadministered with a drug known to cause_______. Three examples are…
low; displacement interactions
Warfarin, phenytoin, and tolbutamide
How do you calculate drug doses for neonates/infants?
mg/kg (remember adults are given a standard dose
Peds- as you increase TBW and EC what happens to VD for hydrophilic drugs?
increases
Elderly- as TBW decreases, what happens to Vd for hydrophilic drugs?
also decreases; this results in higher serum levels
Elderly during acute illness
- decrease in plasma protein (albumin)
- increase alpha 1 acid glycoprotein
- increase % of unbound drug
- decrease % of unbound drug (basic)