Week 2 Flashcards by Kate Niznik

Drugs are biologic active substances that can modify

Cell function

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Terms used to measure drug response or ACTION

Dose response curve
Potency
Efficacy

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Describe dose effect curve

Dose of a drug (amount) given with a measured effect (response)

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On a dose effect curve graph what does x axis represent and what does h axis represent

X axis - increasing dose
Y axis - increasing effect of the drug

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Describe what the therapeutic effect looks like on a graph

As dose (x axis) increases the effect is 0 at first then a quick increase effect

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What does EC50

Effective concentration of drug is needed to get half of maximum effect

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What is potency

The amount of drug to provide an effect

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Potency is shown by the location along the

Log dose axis (x axis )

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10mg of morpheme has the same effect as 100mg of meperidine therefore which is more potent?

Morphine

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More potent drugs can reach _____ levels at lower doses

Toxic

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What is the maximum intensity of effect (response) that can be produced by a drug no matter the dose

Maximal effect

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If drug dose is increased after maximal effect it may increase chance for an?

Adverse reaction

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Efficacy indicates?

Drug action

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What is the therapeutic index (TI)

Ratio of median lethal dose (LD50) to the median effective dose (ED50)
* TI = LD50/ED50

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What is LD50

Death dose in 50% of test animals

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What is ED50

Dose required to produce desirable effect on 50% of tested animals

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The higher the therapeutic index (TI)

The safer the drug

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Drugs do not perform a new function on the organism, either the drug produces the same ____ or ____

The same action as an endogenous agent or block the action of the endogenous agent

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Endogenous agents are

Any chemicals produced in your body (ex hormones)

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Drug must bind to a ____ on the cell membrane to exert an effect

Receptor

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What are drug receptors

Many large molecules (proteins) either on the cell membrane or within the cell

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Usually specific drug binds with a specific receptor, what action is happening?

Lock and key

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Drug receptor interactions are

Weak chemical bonds

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Different drugs compete for same receptor sites, stronger ____(more potent) binds with more receptors than weaker _____ (less potent) drugs

Affinity for both blanks

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Describe agonist drugs

Naturally occurring neurotransmitters (NTs)

Describe process of agonist drugs

Affinity for a receptor Combines with receptor Produces an effect

Antagonist drugs do what?

Counteracts agonist drugs

What are the 3 types of antagonist drugs

Competitive antagonist Non competitive antagonist Physiologic antagonist

Describe the mechanism for competitive antagonist

Affinity for receptor Combines with receptor Produces no effect

Describe the mechanism of a noncompetitive antagonist

Binds to a different receptor site than antagonist Reduces maximal response of agonist

Describe mechanism of physiologic antagonist

Affinity for a different receptor than agonist Decreases maximal response of the agonist by producing an opposite effect via different receptors

Amount and rate of drug passing through cell membrane are important in what 2 things

Time course of action Individual response

Membranes are composed of (3)

Lipids Proteins Carbohydrates

Lipid soluble substance moves across the lipoprotein membrane by passive transfer called

Simple diffusion using a concentration gradient (from high to low concentration)

Water soluble substances have difficulty passing through

A lipoprotein membrane

In active transport substances are transported

Against a concentration gradient Blocked by metabolic inhibitors Mediated by transport “carriers” with energy

Facilitated diffusion does not

Move against a concentration gradient

Factors that influence the movement of drugs are in 4 major steps (ADME)

Absorption Distribution Metabolism Excretion

Absorption refers to the process where drug molecules are transferred from where to what?

From administration site to circulating blood, passing through biologic membranes

What 3 things influence rate of absorption

Physiochemical factors Site of absorption Solubility

Weak electrolyte drugs dissociate (separate) in solution (pKa) and break into?

Un-ionized and ionized forms

Describe un ionized

Uncharged non polar lipid soluble EASILY crosses cell membrane

Describe ionized

Charged polarized less lipid soluble DIFFICULT to cross cell membrane

What 2 things will determine the amount of drug present in ionized and un ionized states

pH of site of administration and dissociation characteristics

Weak acids are better absorbed when

pH is less than pKa

Weak bases are better absorbed when

The pH is greater than the pKa

Release of dose from a tablet or capsule follows what 4 steps in oral absorption

Disruption (of coating) Disintegration Dispersion Dissolution (dissolved in GI fluid)

Drug in solution skips the oral absorption steps and usually a quicker

Onset of action

Absorption from injection site; if the drug has low solubility then it has a ____ duration

Longer

Drugs occur in 2 forms in the blood

Bound to plasma proteins (reservoir for the drug) Free drug (pharmacological effect b/c it only passes through cell membrane)

Distribution is the passage of drugs into various body fluid compartments for an

Action

What are some factors of distribution

Size of the organ Blood flow of the organ Solubility of the drug Plasma protein binding capacity Barriers

Biologic activity of a drug is related to

Concentration of the free or unbound drug in the plasma (This is the biologically active drug)

drug interaction happens when one drug is bounded and another highly bounded drug displaces the first drug from plasma protein binding sites increasing what?

The effect of the first drug

Blood brain barrier; to penetrate the CNS depends on the (2)

Drugs lipid solubility and degree of ionization

What is a highly lipid soluble un ionized drug easily penetrates the blood brain barrier to access CF and induce sleep seconds after IV

Thiopental

In what kind of circulation are metabolites secreted via bile into intestine and continue with some drug being excreted in the cycle

Enterohepatic circulation

Enterohepatic circulation allows for ?

Prolonged effect of the drug

Drugs get ____ if it goes to a non specific site

Terminated

Metabolism (bio transformation): produces compounds that are more

Polar and more easily excreted (Mostly in the LIVER)

Metabolite is more ____ and ____ soluble therefore renal reabsorption with be _____ b/c reabsorption favours lipid soluble metabolites

Polar and lipid soluble Reduced

Metabolism is what kind of process

Enzyme dependent process

What are the 3 ways drugs metabolize

Active to inactive Inactive to active Active to active