Term
| What is the Henderson-Hasselbach equation for a weak acid? |
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Definition
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Term
| What is the Henderson-Hasselbach equation for a weak base? |
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Definition
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Term
| What are characteristics of zero order kinetics? |
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Definition
- Constant amount of drug eliminated per unit time independent of concentration
- Half-life is not constant (DNE)
- Straight line with linear Y and X scales
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Term
| What are the characteristics of first order kinetics? |
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Definition
- Constant fraction of drug eliminated per unit time, although amount changes
- Half-life is constant
- Log transformation yields a linear line
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Term
| What is loading dose and its equation? |
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Definition
Amount that promptly raises the concentration of drug in plasma to the target concentration.
Loading Dose = Vd x TC |
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Term
| What is the volume of distribution (Vd) and its equation? |
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Definition
The measure of the apparent space in the body available to contain the drug.
Vd = Dose/C0 |
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Term
| What are the classic enzyme inducers (5)? |
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Definition
| clofibrate, dexamethasone, phenobarbital, phenytoin, rifampin |
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Term
| What are the classic enzyme inhibitors (5)? |
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Definition
| allopurinol, chloramphenicol, cimetidine, erythromycin, ketoconazole |
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Term
| What are the classic drugs that alter stomach pH? |
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Definition
| antacids, H2-receptor antagonists, proton-pump inhibitors |
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Term
| What are the classic drugs that alter GI absorption? |
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Definition
| cholestyramine, sucralfate |
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Term
| What is the extraction ratio (ER) and its equation? |
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Definition
The effect of first-pass hepatic elimination on bioavailability or the % of a drug extracted by a particular organ.
ER = CL/Q; where Q is blood flow |
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Term
| What is half-life (T1/2) and its equation? |
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Definition
Time required to change the amount of drug in the body by one-half during elimination.
T1/2 = (0.693 x Vd)/CL |
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Term
| What is the dosing rate for IV drugs and its equation? |
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Definition
The rate that must equal the rate of elimination to achieve a steady state (ss).
Dosing RateIV= Rate of eliminationIV = CL x TC |
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Term
| How do you correct dosing rate for a route that has a bioavailability less than 100% ie, oral? |
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Definition
| Dosing rateoral = Dosing rate/Foral |
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Term
| What is maintenance dose and its equation? |
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Definition
The amount given as intermittent doses to maintain target therapeutic concentration.
Maintenance Dose = Dosing Rate x Dosing Interval |
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Term
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Definition
| pH at which 50% of the drug is ionized. |
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Term
| What is the difference between pharmacokinetics and pharmacodynamics? |
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Definition
| Pharmacokinetics is what the body does to the drugs and pharmacodynamics is what the drugs do to the body. |
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Term
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Definition
| Drugs that binds to and activates the receptor in some fashion. |
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Term
| Define pharmacologic antagonist. |
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Definition
| Drug that by binding to a receptor, competes with and prevents binding by other molecules. |
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Term
| Define allosteric inhibition. |
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Definition
| Drugs that bind to the same receptor molecule but do not prevent binding of the agonist; this inhibition is not overcome by increase the dose of the agonist. |
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Term
| Define constitutive activity. |
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Definition
| Physiologic effect that occurs even in the absence of any agonist, indicating that some of the receptors are in the active form some of the time. |
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Term
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Definition
| Agonist drugs that activate receptor-effector systems to the maximum extent to which the system is capable. |
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Term
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Definition
| Drugs that bind to the same receptors and activate them in the same way but do not evoke as great a response, no matter the concentration. |
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Term
| What two characteristics are important in order for a molecule to be a receptor? |
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Definition
| It must be selective in choosing ligands to bind and it must change its function upon binding so that it alters the activity of a biologic system. |
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Term
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Definition
| Inactive precursor chemical that is readily absorbed and distributed then converted to the active drug by biologic processes. |
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Term
| What is aqueous diffusion driven by? |
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Definition
| The concentration gradient of the permeating drug. |
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Term
| What is Fick's Law of Diffusion and its equation? |
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Definition
The passive flux of molecules down a concentration gradient.
Flux (molecules per unit time) = (C1-C2) x [(Area x Permeability coefficient)/Thickness]
where C1 is the higher concentration and C2 is the lower concentration |
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Term
| What is the neutral form of a weak acid and a weak base? |
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Definition
| Protonated form of the weak acid and unprotonated form of the weak base is the neutral lipid-soluble form. |
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Term
| Where are all drugs filtered at? |
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Definition
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Term
| In what conditions are weak acids and bases excreted faster? |
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Definition
| alkaline urine for weak acids and acidic urine for weak bases |
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Term
| What are "orphan" receptors? |
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Definition
| Those which ligands are presently unknown. |
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Term
| What kind of curve describes the relation between drug concentration and effect? |
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Definition
| hyperbola, indicating that responses to low doses of a drug usually increase in direct proportion to dose |
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Term
| What is the concept of "spare" receptors? |
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Definition
| If it is possible to elicit a maximal biologic response at a concentration of agonist that does not result in occupancy of the full complement of available receptors. |
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Term
| How do some receptor agonists bind to the receptor irreversibly? |
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Definition
| Forms a covalent bond with the receptor or binds so tightly that the receptor is unavailable for binding of agonist. |
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Term
| What is the duration of action of an irreversible antagonist independent and dependent of? |
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Definition
| Independent of its own rate of elimination and dependent of the rate of turnover of receptor molecules. |
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Term
| What is potency of a drug? |
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Definition
| The concentration (EC50) or dose (ED50) of a drug required to produce 50% of that drug's maximal effect. |
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Term
| What two things do the potency of a drug depend on? |
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Definition
| The affinity (Kd) of receptors for binding the drug and the efficiency with which drug-receptor interaction is coupled to response. |
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Term
| What do quantal dose-effect curves show? |
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Definition
| Dose of a drug required to produce a specified magnitude of effect in a large number of indvidual patients or experimental animals. |
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Term
| What is the median effective dose (ED50)? |
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Definition
| Dose at which 50% of individuals exhibit the specified quantal effect. |
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Term
| What is the median toxic dose (TD50)? |
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Definition
| Dose required to produce a particular toxic effect in 50% of animals. |
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Term
| What is median lethal dose (LD50)? |
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Definition
| Dose required to cause death in 50% of the animals. |
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Term
| What is maximal efficacy? |
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Definition
| The limit of the dose-response relation on the response axis. |
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Term
| What is the therapeutic index? |
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Definition
| Relates the dose of a drug required to produce a desired effect to that which produces an undesired effect. |
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Term
| What is an idiosyncratic drug response and what may cause it? |
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Definition
| Response that is infrequently observed in most patients; can be due to genetic differences in metabolism of the drug or by immunologic mechanisms. |
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Term
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Definition
| When responsiveness diminishes rapidly after administration of a drug. |
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Term
| What four general mechanisms may contribute to variation in drug responsiveness? |
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Definition
- Alteration in concentration of drug that reaches receptor
- Variation in concentration of endogenous receptor ligand
- Alterations in number or function of receptors
- Changes in components of response distal to the receptor
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Term
| What are three therapeutic strategies to avoid/mitigate toxicity? |
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Definition
- Drug should always be administered at the lowest dose that produces acceptable benefit.
- Adjunctive drugs that act through different receptor mechanisms may lower the dose of the first drug
- Selectivity of drug's actions may be increased by manipulating the concentrations of drug available to receptors in different parts of body
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Term
| What is clearance (CL) and its equation? |
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Definition
It is the factor that predicts the rate of elimination in relation to the drug concentration.
CL = Rate of elimination/Concentration |
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Term
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Definition
| The fraction of unchanged drug reaching the systemic circulation following administration by any route. |
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Term
| What two factors is the rate of absorption determined by? |
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Definition
| Site of administration and the drug formulation. |
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Term
| How is the drug converted in Phase I reactions? |
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Definition
| The parent drug becomes a more polar metabolite by introducing or unmasking a functional group. |
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Term
| What is the first-pass effect? |
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Definition
| Upon administration, the drug is absorbed intact from the small intestine and transported first via the portal system to the liver, where it undergoes extensive metabolism. |
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Term
| What classes of enzymes are important for oxidative drug metabolism in smooth microsomes? |
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Definition
| Mixed function oxidases (MFOs) or monooxygenases. |
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Term
| What are the two microsomal enzymes that play a key role in oxidation-reduction? |
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Definition
| NADPH-cytochrome P450 reductase and cytochrome P450. |
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Term
| What occurs in Phase II reactions? |
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Definition
| Phase I metabolites undergo coupling or conjugation to yield drug conjugates, which are polar molecules that are readily excreted and often inactive. |
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