Quantitative pharmacokinetics part 1 Flashcards by Murielle Nsiela

What is volume distribution?

The volume of plasma that would be required to contain the drug dose at the concentration measured in plasma.

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Volume distribution can be greater than total volume of a human due to tissue binding. TRUE OR FALSE?

TRUE

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From desired C and knowing VD we can estimate the required dose. TRUE OR FALSE?

TRUE

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What is clearance?

volume of plasma cleared of drug per unit time

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What is clearance used to estimate?

Used to estimate rate of elimination of the drug

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What is the equation for rate of elimination?

Rate of elimination = Cl x C

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What is the equation for calculating dose?

Dose = Cl x AUC∞

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By measuring AUC∞ we can calculate Cl. TRUE OR FALSE?

TRUE

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How can clearance be measured?

By measuring the area under the curve

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What is half life?

The time required for elimination of half of the absorbed drug

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What is a first order process?

The Rate is proportional to one variable/ rate is dependent on drug

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What is a zero order process?

It depends on zero variables/ Rate is constant and doesn’t change with [Drug]

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What is extraction ratio?

Is the fraction of drug entering a tissue that is eliminated

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What does C0 mean?

concentration of drug in plasma at t=0 (immediately after administration)

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What is the equation fro exponential decay?

C=C0e-kt

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What does K mean in the exponential decay equation?

elimination rate constant, fraction of drug eliminated per minute

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What is the equation for calculating half life?

kt½ = ln 2

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If know k, can calculate t½. TRUE OR FALSE?

TRUE

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If you know Vd you can calculate the dose for any give n concentration. TRUE OR FALSE? and provide equation for this

TRUE

VD = Dose/C0

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What is Intravenous Infusion?

Drug delivered over minutes-hours

What are the reasons/benefits for having Iv infusion?

allows precise and controlled exposure
– adjust concentration
– stop if required
– short infusion sometimes used to reduce Cmax and adverse events following rapid bolus injection

What is the equation that helps to describe the relationship between clearance and elimination rate constant?

k = Cl/VD

If clearance is big the half life will be small and vice versa. TRUE OR FALSE?

TRUE

The half life is controlled by how much volume of the drug appears to be dissolved in and by what volume of plasma is cleared per unit time . TRUE OR FALSE?

TRUE

What occurs when drug concentration increases to a plateau value Css? and what is the equation that describes this?

Rate of elimination is equal to rate of infusion | C = Css(1-e^-kt)

What does this equation describe? C = Css(1-e^-kt)

Concentration in plasma gets exponentially closer to Css as time progresses but it never reaches it

What is a loading dose useful for?

Useful to quickly reach Css | bolus iv dose

What is the equation for required rate of infusion?

Rinf = Cl x Css

What is the equation for loading dose?

Loading dose = Css * VD

How many half life's does it take to reach 90% of plateau?

3.3 t½

Plateau concentration determined by infusion rate and clearance Increasing the infusion rate will increase the final Css. TRUE OR FALSE?

TRUE

Time to reach plateau depends on the elimination constant (or t1/2). Increasing the infusion rate will NOT REDUCE the time to reach Css because Css will be increased. TRUE OR FALSE?

TRUE

What is Linear pharmacokinetics?

pharmacokinetic parameters don’t change with dose | – increasing dose increases exposure

What is Non-linear pharmacokinetics?

– Pharmacokinetic parameters change with dose of drug | – increasing dose has a disproportionate effect on exposure

Rate of increase of | drug in body = Rate of absorption - Rate of elimination . TRUE OR FALSE?

TRUE

what is the difference in terms of Cmax and Tmax in P.o compared to I.v?

reduced Cmax | increased Tmax

What is meant by "Absorption can become rate-limiting" in P.O administration?

Rate of absorption controls rate of elimination, only happens when absorption is slow and rate limiting

What is Bioavailability?

Fraction of administered drug that reaches the systemic circulation

In I.V administration all drug is not systemically available . TRUE OR FALSE?

FALSE

Non i.v. – some drug may not reach systemic circulation. TRUE OR FALSE?

TRUE

What equation can be used to calculate the amount of drug reaching systemic circulation?

F x Dose (Bioavailability * Dose)

Why is bioavailability important ?

because we want to determine the dose of drug to give a patient, so we need to know the proportion that gets absorbed

What equation is used to measure bioavailability for P.o?

Fpo = Doseiv * AUCpo/Dosepo * AUCiv

How can Bioavailability be measured?

By measuring AUC we can determine F

If the doses are equal, F is simply the ratio of the two AUC values. TRUE OR FALSE?

TRUE

What is the constant steady state Css dependent upon?

Depends on dose & frequency

What is the equation to calculate dose for P.o taking into consideration bioavailability?

Dose = t * Cl *Css, av/ F

What is a loading dose?

An initial “high” dose of drug to quickly plasma drug concentration to the desired level – particularly important for drugs with large VD

What is Maintenance dose?

Once desired plasma drug concentration is achieved, them maintenance dose compensates for drug elimination