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75 Cards in this Set
- Front
- Back
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Pharmacodynamics Definition
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Relationship between drug concentration and pharmacologic effect on body
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Agonist Definition
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Substances that directly change cell function by binding to the receptor.
Drug binds to receptor and activates it. |
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Antagonist Definition
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Drug that binds to receptor without activating & at same time prevents an agonist from stimulating it
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Competitive Antagonist Definition
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Bind reversibly to receptors. Can be displaced by higher concentrations of agonists
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Noncompetitive antagonist Definition
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Bind to receptor with such affinity that even high concentrations of an agonist can not reverse blockade
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Hyper-reactive definition
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Unusually LOW dose of drug produces expected pharmacologic effect
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Hypersensitive definition
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Allergic type reaction
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Hypo-reactive definition
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Unusually LARGE dose of drug for expected pharmacologic effect
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What is Tolerance?
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Hypo-reactivity acquired from chronic exposure to a drug
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What is Tachyphylaxis?
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Tolerance that develops ACUTELY with only a few doses of a drug. Can be seen in Ephedrine.
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How does Ephedrine increase BP indirectly?
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Endogenous release of norepi
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How does Ephedrine increase BP directly?
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Direct stimulant effects on adrenergic receptors
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How does Ephedrine cause tachyphylaxis?
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Persistent occupancy of adrenergic receptors. Also depletion of norepi stores.
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What are some mechanisms of tolerance?
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Enzyme induction-CP450
Depletion of neurotransmitter - sustained stimulation; Immunity- from formation of antibodies |
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What is the additive effect?
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Second drug acting with first drug to produce effect equal to summation.
1+1=2 |
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What is synergism?
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Two drugs interact to produce an effect greater than the summation.
1+1=3 |
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What is potentiation?
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Enhancement of first drug by second drug that has nothing to do with the first.
0+2=3 |
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Anaphylaxis is what type of response?
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Immune-mediated response allergic reaction to a foreign substance. IgE mediated
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What are percentages of different anaphylactic reactions seen under anesthesia?
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CV symptoms: 73.6%
Cutaneous: 69.6% Bronchospasm: 44.2% |
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How does anaphylactoid reaction differ from anaphylaxis?
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Clinically indistinguishable but not IgE mediated. Both equally life threatening
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What is pharmacokinetics?
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"What the body does to the drug" Branch of pharmacology dedicated to the determination of the fate of substances administered externally to a living organism
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What is distribution?
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Reversible transfer of a drug from one compartment to another within the body
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Drug concentration after distribution is based from...
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#1) Dose administered
#2) Extent of distribution of drug into the tissues (Lipid or Water soluble) |
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Average total body water, intracellular fluid, and extracellular fluid for Male?
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BW- 45% of body weight
ICF- 25% ECF- 20% |
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Average total body water, intracellular fluid, and extracellular fluid for Female?
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BW- 55% of body weight
ICF- 35% ECF- 20% |
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What are the volume of distribution body compartments?
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Plasma Volume, Interstitial Volume, Intracellular Volume, and Adipose tissue
Extracellular volume = PV+ISV |
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What is the volume of distribution definition?
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"Apparent" volume into which a drug distributes in the body at equilibrium BEFORE elimination starts
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What is the calculation for volume of distribution?
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Vd=A/C
= total dose or Amount in body at equilibrium) / plasma drug concentration |
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If the Vd is larger, then?
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The fraction in the plasma is smaller and is more readily dissolved in adipose tissue.
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What are some disease states that alter Vd?
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Renal Failure
Hepatic dysfunction Age/body composition CHF/shock Burns Gender Bypass machine (hemodilution) |
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What are drug factors that affect Vd?
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-Degree of binding to plasma proteins
- Partition coefficient of the drug in fat - Degree of binding to other tissues -pH of the drug in blood |
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In the one compartment model, drug distribution is...?
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Assumed to be instantaneous and concentration can only decrease by elimination from the system.
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An IV drug in the two compartment model follows what path?
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Initially in central compartment, then distributed to peripheral compartment where it builds up, finally back to central compartment for excretion
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The Alpha phase relates to?
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Distribution
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The Beta phase relates to?
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Elimination
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The VRG makes up what percent of mass but receives how much of CO?
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Includes main organs making up 10% of body mass but receives 75% of CO
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The principle absorption site after oral administration is "blank" and goes through?
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Small intestine and undergoes first pass hepatic effect for extensive extraction and metabolism
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What is drug absorption?
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Process by which drugs are delivered to blood in their active form.
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The 5 determinants of drug absorption are?
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1. Route of administration
2. Transport across membranes 3. Bioavailability of the drug 4. Protein binding 5. Degree of ionization |
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Passive transport of drugs across membranes consists of?
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A superficial covering of proteins and central cor lipid bilayer. The membrane has polar and nonpolar compounds while drugs have lipid and water soluble properties to facilitate transfer
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Aqueous diffusion or filtration in drug transport involves?
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Flow of water that occurs as a result of hydrostatic pressure or osmotic differences across a membrane.
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The 5 determinants of the rate of diffusion are?
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1. Drug concentration
2. Drug molecular weight 3. Diffusion surface area 4. Temperature 5. Diffusion distance |
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Rapid transfer of organic substances across membranes can be done by?
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Carrier mediated active transport.
Ex: facilitated by glucose and amino acids |
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What is pinocytosis?
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Molecules are placed in small vesicles and then cross the cell membrane
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The free-unbound portion of a drug is?
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ACTIVE
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Drugs with high protein binding have a?
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Longer duration of action
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Drugs with low protein binding have?
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Shorter duration of action b/c large amount is free and active thus already in central compartment and can get eliminated
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The 3 plasma proteins that drugs bind to are?
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1. Albumin (most abundant)
2. Lipoproteins 3. Alpha-1 acid glycoprotein's |
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Increases in Alpha-1 acid glycoprotein (a plasma protein) occur by?
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1. Surgery
2. Chronic pain 3. Acute MI 4. Rheumatoid arthritis |
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Increases in plasma proteins cause...
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Increased protein binding by drugs and therefore less active drugs
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The 4 determinants of protein binding are?
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1. Total drug concentration
2. Drugs affinity for protein 3. Protein concentration in patient 4. pH of plasma |
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The elderly or those with poor nutrition likely have "blank" and causes "blank"
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hypoalbumin and are therefore more sensitive to drugs
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A drug that is un-ionized is...?
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Uncharged, Lipid soluble/hydrophobic, and crosses membranes easily.
Better absorption from renal tubules, GI tract, and increased metabolism by hepatocytes. |
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A drug that is ionized is...?
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Charged, water soluble/hydrophyllic, and does not cross membranes easily.
Impaired GI absorption, greater renal excretion of drugs, and poor metabolism by hepatocytes. |
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What is a drugs pKa?
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The pH of a drug at which 50% of the drug is ionized and 50% is un-ionized.
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An acid does what with protons?
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Acid is proton donor (gives up H+ ions)
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A base does what with protons?
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Base is proton acceptor (accepts H+ ions)
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A weak acid will...?
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Weak acid becomes increasingly un-ionized (active) as the pH of the environment DECREASES
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In a weak acid when: pH<pKa
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Causes increased unionized (active)
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In a weak acid when: pH>pKa
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Causes decreased unionized or increased ionized
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Acid + Acid =
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Unionized
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Examples of weak acids are?
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Form salts with positively charged ions such as Na+, Mg++, or Ca+.
Ex: sodium pentathol |
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A weak acid will...?
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Weak acid becomes increasingly un-ionized (active) as the pH of the environment DECREASES
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In a weak acid when: pH<pKa
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Causes increased unionized (active)
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In a weak acid when: pH>pKa
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Causes decreased unionized or increased ionized
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Acid + Acid =
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Unionized
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Examples of weak acids are?
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Form salts with positively charged ions such as Na+, Mg++, or Ca+.
Ex: sodium pentathol |
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In a weak base: pH<pKa
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More ionized (inactive)
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In a weak base: pH>pKa
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Less ionized or more active
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Base +Base =
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Unionized
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Examples of weak bases are...
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Form salts with NEGATIVELY charged ions such as Cl-, or a sulfate.
Ex: locals like lidocaine hydrochloride or morphine sulfate |
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A drugs degree of ionization is dependent on 3 things...?
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1. Nature of the drug (acid/base)
2. pKa of the drug 3. pH of the environment |
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Adding bicarb to a weak base such as local anesthetic will increase or decrease the speed of onset?
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Increase the speed. Base+Base=unionized so rate of diffusion is increased as well as speed of onset
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Explain ion trapping in the case of a fetus and a weak base
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Drug in unionized form in mother and easily crosses membranes to more acidic child. Drug becomes more ionized around fetus and is unable to cross back over lipid membrane becoming trapped.
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Injecting local into infected tissue has what effect on the drug?
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Delays onset of local b/c of acidic environment of infection and base of local creating more ionized drug. Unable to penetrate membranes necessary for neural blockade.
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