Pharmacokinetics Flashcards

1
Q

What does phase 1 of drug metabolism in the liver involve?

A

Cytochrome P450 enzymes in the liver (very versatile enzymes) strip groups off the drugs to expose their functional groups and make them more reactive. This involves oxidation, reduction, hydrolysis, deamination.

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2
Q

What does phase 2 of drug metabolism involve?

A

The molecule is conjugated to glucuronic acid, amino acids (e.g glycine), or sulphuric acid, so that it is water soluble and can be excreted by the kidney.

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3
Q

What is the first pass effect?

A

Drugs taken orally are absorbed into the portal vein and taken to the liver before entering the whole circulation, so a fraction of the drug is already inactivated and metabolised before it reaches the rest of the circulation.

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4
Q

What is the difference between a partial agonist and a full agonist?

A

A partial agonist binds to the receptor but only has partial efficacy, so has a decreased tendency to activate the receptor (can’t produce maximal response even if higher concentration applied).

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5
Q

What is the dose ratio?

A

The dose ratio is defined as the ratio by which the agonist concentration has to be increased in the presence of the antagonist in order to restore a given level of response.

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6
Q

What is an irreversible antagonist?

A

Ligand that binds covalently to the binding site on the receptor, and so can’t be displaced by either competitive ligands or washing.

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7
Q

Give three examples of drug targets.

A

G protein coupled receptors, ion channels, receptor tyrosine kinases.

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8
Q

What is tachyphylaxis?

A

Rapidly diminishing response to successive doses of a drug, rendering it less effective over time. The effect is common with drugs acting on the nervous system.

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