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25 Cards in this Set
- Front
- Back
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Pharmacokinetics
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study of drug movement throughout the body.
1)absorption 2)distribution 3)metabolism 4)excretion |
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Pharmacodynamics
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study of biochemical and biophysical effects of drugs and the molecular mechanisms by which those effects are produced. ("what drugs do to the body and how they do it.")
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Pharmacokinetics: Absorption
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Movement of drug into the bloodstream.Transfer of a drug from site of administration to the blood. Bioavailability
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Bioavailability
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the fraction of drug that reaches the systemic circulation; 100% for IV drugs
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Pharmacokinetics: Distribution
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Blood<--> ECF and/or cells. Depends on blood flow, capillary permeability, protein binding, hydrophobicity (lipophilicity) of a drug. Effected by volume distribution and protein binding
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Pharmacokinetics:Absorption mechanisms of movement
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Moves by: Passive diffusion-most drugs, concentration grad, Fick's.
Active Transport: absorption from GI track, depends on ATP Protein Binding:bound portion sequestered (prevents further absorption) Effect of pH |
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Volume of distribution
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Involved in Pharmacokinetics. Hypothetical volume into which a drug is distributed. Doesn't represent an actual volume.
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Protein Binding
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Inactive reservoir. Needs to be unbound in order to be released.
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Drug Metabolism
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Biotransformation and exrection
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Polarity
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Polar molecules have an uneven distribution of electrons within the molecule but no net charge.
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Ions
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Ions have a net charge. Rule of solubility is "like dissolves like"=Things without a charge are lipophilic because they dissolve in lipids which also have no charge. Thing with a charge are more likely to dissolve in water (b/c of the charge).
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Non-ionized form of a drug
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Active from of drug
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When talking about acid/base status, ionization of a drug, the response you see in a pt is called...
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the onset of action (pKa:
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Acid drugs
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are proton donors. give up H+.
HA<-->H+ + A- HA= non-ionized from A-=ionized form Ex: ASA |
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Basic Drugs
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Proton acceptors. Take a H+
B+H+<-->BH+ BH+=ionized form B=non-ionized form Ex: Tylenol |
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Characteristics of Non-ionized drugs
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-Pharmacologically active
-Soluble in Lipids (the more lipid soluable a drug is, the more it can cross the membrane) -Can cross lipid barriers (i.e. GI tract, BBB, placenta) -No renal excretion -Hepatically metabolized |
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Characteristics of Ionized drugs
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-Pharmacologically INACTIVE
-Soluable in water -Can't cross lipid barriers -Renally excreted (b/c it doesn't get reabsorped) -Not hepatically metabolized |
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Parameters for Drug Kinetics
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Potency, onset of action and duration of action
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pKa
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The pH(environmental) at which the drug is 50% ionized and 50% nonionized. Important factor in determining drug onset b/c only the nonionized fraction will readily cross the lipid bilayer.
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Volume of Distribution (Vd)
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-More widely distributed the drug, the larger the duration of action.
-The more protein bound, the larger the duration. |
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Ion Trapping
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The process of a drug accumlating on the side of the membrane where pH most favors it ionization. Important in accumlation of drugs of where you don't want them to be.
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In ion trapping, where do acid and basic drugs accumlate?
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Acid drugs=on alkaline side
Basic drugs=acidic side |
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Bioavailablility
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How much of the drug is available once put into the body. IV is 100% with most rapid onset.
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Distribution to the 4 tissue groups
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1) VPG-Vessel poor group
2) VRG-vessel rich group (brain, kidneys, liver) 3) FG-Fat group 4) MG-Muscle Group |
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Tissues groups- cardiac output vs. body mass demand
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VRG has only 9% of body mass, but 75% of the cardiac output. In contrast, FG has 19% body mass, and 7% cardiac output. Represents a whole lot more tissue, but not as much perfusion.
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