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10 Cards in this Set

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What is bioactivation?
Refers to the process by which an inactive xenobiotic is metabolized by the body to an active form

E.g. codeine converted to morphine
What is the "first pass" effect?
Drugs administered orally and absorbed through the gastrointestinal effect will pass through the portal vein and through the liver.

In drugs with a high first pass effect, the liver excessively metabolizes the drug right away and very little drug reaches the systemic circulation.
What is first order metabolism?
First order metabolism occurs when a constant FRACTION of the remaining drug is metabolized per unit time (e.g. 50% per unit time)

In other words, the the rate of metabolism increases with the amount of drug in the system. The enzyme system adapts.

Clinical relevance: it's easy to predict what effect altering a dose will have on blood levels
What is zero order metabolism?
Zero order metabolism occurs when a constant AMOUNT of the remaining drug is metabolized per unit time (e.g. 1 mg per unit time as opposed to 50% per unit time)

In other words, the rate of metabolism is constant and independent of the amount of drug in the system. Metabolism doesn't speed up with more drug, just keeps chugging away at the same rate.

Practically speaking, it is very difficult to predict what effect increasing the dose will have on blood levels
Besides the liver, name 2 organs that may play a significant role in drug metabolism:
Small intestine

Kidney
What are the phases of metabolism?
Phase I: Oxidation, reduction, hydrolysis
Phase II: Conjugation, rendering the xenobiotic hydrophilic
What happens in phase I metabolism?
Oxidation, reduction, or hydrolysis

Exposure or addition of polar groups, setting the stage for phase II to make compound hydrophilic
What is phase II metabolism?
Conjugation

A molecule endogenous to the body donates a part of itself to the xenobiotic, rendering the xenobiotic hydrophilic
What enzyme system of the larger cytochrome P450 superfamily is the responsible for metabolizing 1/3 of all drugs?
CYP3A4
When throwing around "inducers" and "inhibitors," what is actually being induced or inhibited?
Enzymes responsible for metabolizing drugs, like the cytochrome P450 superfamily, can be induced or inhibited and thus metabolize faster or slower than normal