by mtoom

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What is pharmacokinetics?
What the body does to the drug.
What is pharmacodynamics?
What the drug does to the body.
What are the 4 ADME processes?
  • Absorption
  • Distribution
  • Metabolism
  • Excretion
What is absorption?
Movement of drug from site of administration into the blood.
Name 5 things that help you determine what route to use for a drug.
  • Properties of the drug
  • System vs local effects
  • Desired onset of action
  • Patient characteristics
  • Patient compliance
What are the 3 enteral routes of administration?
  • oral (po)
  • sublingual (sl)
  • rectal (pr)
Name 1 pro and 1 con of enteral administration. What is it "also known as"?
Pro: Convenient and inexpensive
Con: 1st pass metabolism (oral)

Also known as via GIT (gastrointestinal tract)
What are the 3 routes of parentral administration?
  • Intravenous (iv)
  • Intramuscular (im)
  • Subcutaneous (sc/subQ)
Name 1 pro and 2 cons of parenteral administration.
Pro: Rapid onset (good if patient unconscious or drug poorly absorbed/unstable in GI)
Cons: Pain, infection
By what process does absorption usually occur?
Passive diffusion
What 4 factors does absorption depend on?
  • Size
  • Lipid solubility (structure, ionization, pH, pKa)
  • Blood flow at site of administration
  • Total surface area for absorption
Write the 2 acid/base equations.
  • HA <> H+ + A-
  • B + H+ <> BH+
What forms of an acid/base drug will be able to cross a lipid bilayer easily?
HA or B
What is the Henderson-Hasselbalch equation?
pH = pKa + log(U/P)

U = Unprotonated
P = Protonated
What is the bioavailability? Give an equation.
The fraction of drug that reaches system circulation.

F = (amount of drug in systemic circulation) / (amount of drug administered)
What is the bioavailability when a drug is given IV?
How do you calculate bioavailability? Give an equation.
The bioavailability is: (AUC oral) / (AUC injected)
What 3 factors does distribution depend on?
  • Blood flow
  • Lipid solubility
  • Protein binding
What do plasma proteins do with regard to ingested drugs, in the blood?
They bind drugs, taking away from the "free drug" in circulation. Dosage of drugs accounts for effects of binding proteins. However, increased binding of drug to plasma proteins can reduce the effectiveness of a drug.
What is meant by administration of a drug?
The dose, or amount given.
How do we calculate the concentration in the body for a given dose? Give an equation.
Concentration = dose / Vd
What is the Vd?
Volume of distribution: A proportionality constant that relates the amount of drug in the body to its concentration in the blood.
What modification (with respect to polarity) does metabolism typically involve?
Making a drug more polar to enhance excretion.
Where does metabolism primarily occur, and what are the 2 phases?
In the liver.

  • Phase I: Oxidation/reduction
  • Phase II: Conjugation
What do Phase I reactions do? What enzymes are involved?
Increase water solubility of drugs by adding or unconvering polar groups.

Enzymes involved: P450
What do Phase II reactions do? What enzymes are involved?
They covalently add large, polar endogenous molecules to parent drug or Phase I metabolite.

Enzymes involved: conjugative enzymes
What are CYPs?
Enzymes of the P450 family
What is induction and inhibition of P450?
Induction: When another drug increases the metabolic activity of P450
Inhibition: When another drug decreases metabolic activity of P450
Name 2 beverages that frequently interact with drugs.
Alcohol and grapefruit juice.
Does drug metabolism result in the loss of pharmacological activity? Is this always the case?
Generally, metabolism reduces pharmacological activity. However, sometimes it can increase pharmacological activity by activating a prodrug (e.g. cyclophosphamide).
What is special about digoxin metabolism?
Bacterial enzymes are involved in its metabolism. Antibacterial drugs can result in an increase in drug concentration (potentially causing toxicity).
What are the 3 key steps in renal drug excretion?
  • Passive filtration of drug at glomerulus (unbound drug)
  • Active tubular secretion (includes bound drug)
  • Passive tubular secretion (uncharged drug can move back into drug; depends on urine pH)
Generall speaking, what is enterohepatic circulation?
When drug is reabsorbed from intestines after being excreted in the bile.
Describe the process of enterohepatic recirculation in detail. What is the effect on the body?
  • Phase II conjugates (e.g. glucoronic acid) are hydrolyzed by bacteria with glucorindase
  • Drug is no longer polar
  • Drug reabsorbed back into circulation
  • Prolongs activity of drug in body
Name 3 ways a drug can be eliminated.
  • Urine
  • Bile
  • Feces
How does the serium [drug] plot relate to ADME?
A can be seen as the [drug] rises, D where the [drug] starts to fall, and M+E as it bottoms out.
What is the Cmax?
The maximum concentration reached in the blood.
What is the Tmax?
The time after dosing at which the Cmax occurs.
What is Tmax for a drug administered by IV?
What are the MTC and MEC?
MTC: minimum toxic concentration
MEC: minimum effective concentration
What is the therapeutic range? Define it in terms of MTC and MEC.
It is the range above MEC and below MTC.
Give the equation for first order elimination.
Ct = C0e-kt
What ist he elimination half-life (t1/2)?
Time required for drug concentration to decrease by half
How many half-lives are required for "drug washout"?
5 half-lives for drug to be "completely" eliminated (by convention)
Is the half-life of drug elimination independent of the route of administration?
What is steady-state? How long does it take to achieve?
It is when the IV infusion rate becomes equal to the elimination rate, and the concentration of drug is constant in plasma. It takes about 5 half-lives for steady-state to be reached after infusion at the appropriate dose is started.
What other rate is the infusion rate equal to? Give an equation.
It is equal to the rate of drug elimination at steady state.

IR = CL x Css 

CL = Clearance = "Volume of plasma from which drug is removed per unit time"
When does peak and trough concentration occur?
When dosing is done at discrete intervals. Concentrations fluctuate around the steady state mean.
What are the 2 dosing options to get to steady state?
  • Just give the steady-state infusion rate and wait for 5 half-lives.
  • Use a loading dose first.
Give an equation for the loading dose.
LD = Ctarget x Vd
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