FA.Pharm.Pharmacodynamics Flashcards by caleb cadis

Km is the…

Affinity of the enzyme for the substrate

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Vmax is directly proportional to the ….

(aka efficiency) is directly proportional to the enzyme concentration

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How does a \/ Km effect affinity?

/\ affinity (/\ potency)

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Lineweaver Burke plot:

/\ y-intercept –> effect on Vmax

\/ Vmax

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Fill in the blank:

On a lineweaver burke plot, the further to the right the x-intercept, the ______ the Km and the ______ the affinity

Greater, Lower

b/c Km and Affinity are indirectly proportional

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Lineweaver Burke:

Competive inhibitors do/do not cross each other?

DO.

Competitive inhibitors cross competitively, while noncompetitive inhibitors do not cross.

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Competitive Inhibitors:

Resemble substrate?
Overcome by /\ [s]?
Bind active site?
Effect on Vmax?
Effect on Km?
Pharmacodynamics?

Resemble substrate? Yes
Overcome by /\ [s]?  Yes
Bind active site?  Yes
Effect on Vmax?  No change
Effect on Km?  /\
Pharmacodynamics? \/ potency

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Noncompetitive inhibitors:

Resemble substrate?
Overcome by /\ [s]?
Bind active site?
Effect on Vmax?
Effect on Km?
Pharmacodynamics?

Resemble substrate?  No
Overcome by /\ [s]?  No
Bind active site?  No
Effect on Vmax?  \/
Effect on Km?  No change
Pharmacodynamics? \/ Efficacy

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Pharmacokinetics:

Volume of distribution relates the ______ to the ______.

Relates the AMOUNT of the drug to the PLASMA CONCENTRATION.

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What disease processes can alter the Vd of plasma-protein bound drugs?

Liver and Kidney disease ( \/ protein binding, /\ Vd )

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Vd formula

Vd= (amount of drug in body) / (plasma drug concentration)

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Drugs with LOW Vd (4-8 L) distribute in ______. These are examples of (small / large) or (charged / uncharged).

Large or charged drugs will distribute primarily in the BLOOD, .: these have a LOW Vd.

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Medium Vd: distributes in the _________ or _________;

General description of this class?

Medium Vd distribute in EXTRACELLULAR SPACE or BODY WATER.

These are SMALL hydroPHILIC molecules that do NOT bind plasma proteins

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High Vd (> body weight): distribute to ______?

General description?

Distribute to ALL body tissues

SMALL lipoPHILIC that STRONGLY bind to EXTRAvascular proteins

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Clearence (CL): relates the _______ to the ______

CL relates the RATE of ELIMINATION to the PLASMA CONCENTRATION

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CL formula

CL = (Rate of elimination of drug [vol. cleared/ time]) / (Plasma Drug Concentration)

= Vd * Ke (elimination constant)

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Half-life (t 1/2): The time required to…

Is a property of what kind of zero/first order elim?

decrease the drug in the body by 50% during constant infusion.

Property of first order elimination

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A drug infused at a constant rate (IV) takes ____ half lives to reach steady state?

4-5 half lives

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of half lives –> concentration:

1–>
2–>
3–>
4–>

1 –> 50%
2 –> 75%
3 –> 87.5%
4 –> 93.75%

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Formula for Half Life

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Half Life = (0.7 * Vd) / CL

Bioavailability (F) is the…

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fraction of administered drug that reaches circulation (F for Fraction)

Bioavailibility (F) for:

IV –>

Oral –>

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IV –> 100%

Oral –> % that survices first pass thru liver or gut

Loading dose calculation

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Loading dose = Cp * Vd / F

Cp –> target plasma concentration

Maintenance dose calculation

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Maintenance dose = Cp * CL / F

Frequency [is / is not] affected by time to steady state but [is / is not] affected by half-life.

Frequency IS NOT affected by time to steady state but IS affected by half-life.

How does renal or liver dz change the maintenance or the loading dose?

\/ maintenance dose NO CHANGE for the loading dose

In Zero-order elim. the ____ is constant regardless of the Cp.

rate of elimination is constant regardless of Cp. Cp \/ LINEARLY with time

Examples of zero-order elimination drugs

Phenytoin, Ethanol, Aspirin ¶ PEA: a pea is round, like the "0" in zero-order

First order elimination: a constant _____ eliminated per unit of time.

a constant FRACTION eliminated per unit of time Cp \/ exponentially with time

[true / false ] ionized drugs are trapped in urine

True. Weak acids get trapped in basic urine Weak bases are trapped in acidic urine

Weak acid drugs (name 3) get trapped in [basic / acidic] urine? Tx:

Phenobarbital, Methotrexate, Aspirin Trapped in basic environments Tx: BICARBONATE RCOOH RCOO- + H+

Weak bases (1 example) are trapped in _____ environments. Tx overdose with ____ Generalized dissociation formula

Trapped in ACIDIC environments Tx overdose with AMMONIUM CHLORIDE RNH3+ <=> RNH2 + H+

Phase 1 metabolism occurs via the ______, and involves _____, _____, and _____ of drugs. This yields [polar / nonpolar], [water soluble / NON water soluble] metabolites, which are often [active / inactive]

Phase 1 metabolism occurs via the CYTOCHROME P450 system, and involves REDUCTION, OXIDATION, and HYDROLYSIS of drugs. This yields POLAR, WATER-SOLUBLE metabolites, which are often ACTIVE.

Phase 2 metabolism: Modifies drugs in 3 ways, _____,_____, and _____. Usually yields [polar / nonpolar], [active / inactive] metabolites which are subsequently _____ by the _____.

Phase 2 metabolism: Modifies drugs in 3 ways, Glucuronidation, Acetylation, and Sulfation. Usually yields very POLAR, INACTIVE metabolites which are subsequently EXCRETED by the KIDNEY.

Phase 2 metabolism mnemonic: GAS

Glucuronidation Acetylation Sulfation ¶ Geriatric patients lose phase I first, therefore ¶ Geriatric patients have GAS (phase 2)

Patients who are slow acetylators have [greater / lesser] side fx from certain drugs. Why? Give 1 drug as an example.

Patients who are slow acetylators have GREATER side fx from certain drugs. Why? Because of the \/ rate of metabolism Ex: Isoniazid (INH) p. 212

Efficacy is defined as the...

Efficacy is defined as the MAXIMAL EFFECT a drug can produce. Analogous to Vmax

Name four broad drug classes that have HIGH efficacy

1. Analgesics 2. Antibiotics 3. Antihistamines 4. Decongestants

Potency is defined as the...

Potency is defined as the AMOUNT of DRUG needed for a GIVEN EFFECT /\ Potency --> /\ Affinity for receptor --> \/ Km

Name 3 broad drug classes with HIGH potency.

1. Chemotherapeutic drugs 2. Antihypertensive (blood pressure) drugs 3. Antilipid (cholesterol) drugs

Competitive agonists [right / left] shift the ∫ curve? [increase / decrease] the [efficacy / potency]?

Competitive agonists right shift the ∫ curve DECREASE the POTENCY Thus, more drug needed to reach same effect. ∫ --> ∫

Noncompetitive antagonists [increase / decrease] the [efficacy / potency]? How does this effect the ∫ curve?

Noncompetitive antagonists DECREASE the EFFICACY. \/ the height of the ∫ (\/ the Vmax)

Pharmacodynamics Partial agonists act at same site as full agonist, but with [increased / decreased] maximal effect. Efficacy is [increased / decreased]? Potency is [increased / decreased]?

Partial agonists act at same site as full agonist, but with DECREASED maximal effect. Efficacy is DECREASED. Potency can be increased or decreased. It is a different variable.

Diazepam + Flumazenil on GABA receptors

Example of Competitive antagonist. Flumazenil is the Tx for a benzo OD.

Example of a Noncompetitive antagonist of Norepinephrine and receptor

Norepinephrine + phenoxybenzamine on A-receptors

Give an example of a Partial agonist and receptor

Morphine + Buprenorphine at opioid µ-receptor Buprenorphine will potentiate withdrawal in an addict

Therapeutic Index is measurement of ______ ______. [steep / flat] slopes that are [near / far apart] are best. Formula? Mnemonic

Therapeutic index is a measurement of DRUG SAFETY. STEEP slopes that are FAR APART are best. LD50 / ED50 ---> Median Lethal (or toxic) dose / Median effective dose. ¶ TILE: TI = L / E

4 Examples of drugs with LOW therapeutic index!!!

1. Theophylline (p.576) 2. Digoxin (p.309) 3. Warfarin (p.395) 4. Lithium (p.499)

FA.Pharm.Pharmacodynamics Flashcards

(48 cards)