Pharmacokinetics and Dynamics Flashcards by Jade Molyneux

Where are water soluble drugs excreted

Urine

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Where are lipid soluble drugs excreted

Can cross the lipid membrane so are reabsorbed in the kidney and are changed to water soluble

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Which type of drugs will reach the tissue

Free drugs–not bound to protein

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CO to lungs

100%

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CO to liver

30%

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CO to kidney

25%

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Bioavailability

How much drug will reach the blood

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First pass metabolism by liver

Until all liver enzymes are saturated by the drug, the drug has no effect

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What form of drug bypasses the first pass liver effect

Sublingual and IV lidocaine

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Fastest route of absorption

Inhalation

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Ionized drug

Water soluble–better excretion

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Non-ionized drug

Lipid soluble–better diffusion

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If pH < Pk

Lots of H+; acidic medium; drug is protonated; non-ionized; lipid-soluble

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If pH > pK

Few H+; basic medium; drug is unprotonated; ionized; water soluble

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Acidification of urine causes

Increased ionization of weak bases and increased excretion

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Alkalization of urine causes

Increased ionization of weak acids and increased excretion

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How to make urine more acidic

Cranberry juice, vitamin C, NH4Cl

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How to make urine more alkaline

Aspirin

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IV administration does not involve

Absorption

100% bioavailability

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2 phases of elimination

Rapid decrease in blood concentration due to tissue distribution
Slower decrease in blood concentration due to metabolism and excretion

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MEC

Minimum effective concentration

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MTC

Minimum toxic concentration

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To be bioequivalent…

2 drugs need to have some bioavailability and rate of absorption

Competition between drugs for plasma protein binding sites may

Increase free fraction of drug and might increase the effects of the displaced drug

Sulfonamides and bilirubin competition

Sulfonamides can displace bilirubin from albumin and cause kernicterus in neonates so sulfonamides are contraindicated in newborns

What can cross placental barrier and BBB

Small, lipid soluble drugs | In pregnancy: water soluble alternatives are safer and drugs with highest plasma protein binding

High volume of distribution

Indicates large tissue distribution due to low plasma protein binding

Low volume of distribution

indicates drug primarily found in the blood due to high plasma protein binding

Drug metabolism

Conversion of drug to more water soluble to be more easily excreted

Phases of drug metabolism

Phase 1: modify drug by oxidation, reduction, hydrolytic reactions Phase 2: conjugation of drug molecule with transferase

Codeine is prodrug for

Morphine | If someone is an ultra-rapid metabolizer they could die

Examples of general inducers

Anti-seizure drugs, Rifampin, HIV drugs, chronic alcohol, glucocorticoids Increase gene expression of CYP enzymes resulting in increased metabolism of other drugs

Examples of general inhibitors of metabolism

Proton pump inhibitors, azoles and macrolides, grapefruit juice, SSRI's, acute alcohol Causes decreased metabolism of other drugs and potential toxicity

Zero-order elimination

Large amount of drugs--toxic level Saturation kinetics Body has to eliminate drug at a constant rate regardless of half life Ex. alcohol, phenytoin, salicylates

First order elimination

Constant fraction is eliminated per unit time Half life is constant Most drugs follow this

Clearance

How much blood is completely cleared of drug per unit time | If drug is renally cleared, only the free fraction is filtered by glomerulus

Clinical steady state is reached at

4-5 half lives

Steady state

Rate in= Rate out

Agonist

Has an effect

Antagonist

Has no effect

Inverse agonist

Has opposite effect

Efficacy

Maximal effect a drug can achieve, irrespective of dose

Higher potency=

Less amount of drug needed to reach 100% efficacy

Physiologic antagonism

2 agonists with opposing action antagonize each other

Chemical antagonism

2 chemicals bind to each other and cancel each other (antedotes)

ED TD LD

Effective dose Toxic dose Lethal dose

Therapeutic index

TD/ED

Phase 1 of FDA oversight

Is drug safe for patients? Involves healthy volunteers usually young males Works out toxicity and pharmacokinetics of drug

Phase 2 of FDA oversight

Does the drug work? Involves patients Compare to placebo or positive control Randomized, double-blind

Phase 3 of FDA oversight

how well does drug work and what are common side effects? | Larger group of patients

Phase 4 of FDA oversight

Post marketing surveillance

Schedule 1 Controlled substances

High abuse liability Low or no medical utility Heroin, marijuana, LSD, PCP

Schedule 2 Controlled substances

high potential for abuse Can be prescribed under restricted conditions Triplicate prescription and no automatic refills Ex. Opiates, Amphetamines

Schedule 3 Controlled substances

Lower risk | Anabolic steroids

Schedule 4 controlled substances

low potential for abuse | Benzodiazepines

Schedule 5 controlled substances

Lowest abuse potential | Cough medication with codeine