Pharmacokinetics Flashcards by Pickle Rick

What are the main causes of alterations in absorption, distribution, metabolism, and elimination?

age
genetic factors
end-organ damage
drug interactions

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What is idiosyncratic?

occur in a small minority of patients
sometimes with low or normal doses
poorly understood

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What is a pharmacodynamic interaction?

interaction between 2 or more drugs that leads to either…
- accentuation/synergism
- attenuation/antagonism

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Do pharmacodynamic interactions directly involve absorption, distribution, metabolism, or excretion?

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What type of interaction changes the basic kinetic properties of absorption, distribution, metabolism, and elimination?

pharmacokinetic interactions

NOT pharmacodynamic

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What is the mechanism of this drug interaction…
tetracycline ABX (tetracycline, doxycycline, minocycline) + antacids

antacid impairs absorption of ABX → ↓ ABX efficacy

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What are the clinical implications of this drug interaction…
erythromycin / clarithromycin / metronidazole / ciprofloxacin / trimethaprim-sulfamethoxazole + warfarin

ABX inhibit the metabolism of warfarin → ↑ serum concentration of warfarin → ↑ risk of bleeding

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What are the clinical implications of this drug interaction…
NSAID + warfarin

Additive effect on ↓ platelet aggregation → additive risk for bleeding (especially GI bleeding)

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What are the clinical implications of this drug interaction…
ASA + warfarin

Additive effect on ↓ platelet aggregation → additive risk for bleeding (especially GI bleeding)

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What are the clinical implications of this drug interaction…
Tramadol + antidepressants (DDI highest risk for MAO-I)

↑ risk of serotonin syndrome

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What is the mechanism and clinical implications of this drug interaction…
Protease inhibitors (indinavir, nelfinavir, ritonavir, saquinavir) + BZD

protease inhibitors are CYP450 3A4 inhibitors → ↓ metabolism of benzodiazepine → ↑ benzodiazepine concentrations → ↑ risk of benzodiazepine side effects (↑ sedation depth and duration)

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What is important to know about drugs affects on pregant people?

increased cardiac output
increased renal blood flow
decreased albumin

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What is important to know about drugs affects on people with diabetes?

gastric stasis
nephrotic syndrome

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What are drug cautions with myasthenia gravis?

Aminoglycosides
Fluoroquinolones
Tetracyclines
Macrolides
Magnesium
Beta blockers
Procainamide
Neuromuscular blocker

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What is a side effect?

unrelated to the affect of the drug

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What is a toxic reaction?

exaggeration of the clinical affect of the drug

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What is an allergic reaction?

immune system response to a substance, potentially causing severe symptoms

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What is pharmacokinetics?

WHAT THE BODY DOES TO THE DRUG
- kinetics, body, drug
KBD

Killer baby deer

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What is pharmacodynamics?

WHAT THE DRUG DOES TO THE BODY

dynamics, drug, body
DDB

Double D’s :)

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How is kinetics used in drug development?

used to determine optimal dose
important in the clinical setting for toxicology, therapeutic monitoring, drug interactions, dose adjustments, effect of illness, organ dysfunction

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Kinetcs focuses on concentrations of drug in the…

plasma

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What is Cp?

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The goal is to get Cp within a therapeutic window in order to elicit appropriate response without causing _________

toxicity

What is MTC vs MEC?

minimum toxic concentration
minimum effective concentration

Where on this graph is a good place to be for the drug to be effective.

between MEC and Cmax

Where is a dangerous level to be on this graph

near/above MTC

What does clearance determine?

maintenance dose-rate

What does the volume of distribution (VD) determine?

the loading dose

What does half-life determine?

the time to steady state and dosing interval

The kinetic parameters for a drug are determined by using what method of insertion?

IV injection or infusion (100% bioavailability)

What is clearance?

- Volume of plasma cleared of drug per unit of time - index of how well a drug is removed irreversibly from the circulation

What is used to determine the dose-rate (dose/unit time) required to maintain plasma concentration of a drug?

clearance

In zero order kinetics the rate of absorption/elimination _______ depend on the drug concentration

does not

What are the rate limiting processes for zero order kinetics?

- fixed number of enzymes, carrier, or active transport proteins - saturation occurs

What drugs use zero order kinetics?

* PHENYTOIN * WARFARIN * HEPARIN * ETHANOL * ASPIRIN (HIGH DOSE) * HALF LIFE (T ½ ) DECREASES OVER TIME * THEOPHYLLINE

In zero order kinetics the half life _________ with decreasing concentration

decreases

In first order kinetics the decline in Cp ________ with concentration

varies

In first order kinetics the half life _________ with decreasing concentration

sames the same

In first order kinetics concentration decreases by ____% per each T 1/2

50%

To maintain a steady state (CPss), administration rate must be equal to rate of...

elimination

What is the volume of distribution (VD)?

volume into which a drug appears to be distributed with a concentration equal to that of plasma

To reach a target Cp (plasma concentration) you have to "fill up the tank" using...

VD (volume of distribution)

VD can or cannot exceed the actual body volume?

It can far exceed it

Drugs with _____ VD tend to be polar and water soluble

small

What is the definition of half-life?

- time of the drug concentration to halve

What does half-life provide an index for...

- time course of drug elimination - time course of drug accumulation - choice of drug interval

It takes approximately ___ half-lives for a drug to either reach steady state (CPss) or be eliminated from the body

What is steady state kinetics?

point at which the amount absorbed equals the amount eliminated per unit of time

What is the equation of half-life?

What is the equation for elimination rate constant?

What is the equation for volume of distribution?

What is the equation for loading dose?

What is the equation for clearance?

What is the equation for steady state concentration (IV)?

What is the equation for steady state concentration (PO)?