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18 Cards in this Set
- Front
- Back
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Define drug biotransformation:
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Reactions with the goal of conversion of a molecule to a more water-soluble (excretion increases) metabolite
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Define elimination 1/2 life
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Time required for blood plasma levels to drop by 50%
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Most drugs undergoe what type of biotransformation? What is the rate of this reaction dependant on?
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Most drugs undergoe first order reactions; the rate is proportional to the amount of drug present
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What type of biotransformation reaction is constant?
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Zero order; DOES NOT depend on amount of drug present, e.g. alcohol
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What are the 4 types of changes that biotransformation Rxns can produce?
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active drug > inactive metabolite (ideal)
active drug > active metabolite (increased attention needed, long 1/2 life) active drug > toxic metabolite (acetaminophin) inactive drug > active metabolite (plavix) |
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Describe Phase I Biotransformational Rxns
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Most drugs undergoe these; produce metabolites more soluble than parent & usually inactive
e.g. oxidation (majority), hydrolysis, reduction |
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What are Phase II Biotransformational Rxns?
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Conjugation rxns; drugs that arent water soluble enough after phase I go through phase II;
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What are three examples of phase II conjugation rxns?
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acetylation
glucuronidation methylation |
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What is the major organ involved in biotransformation?
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LIVER (hepatocytes>smooth ER>enzymes for oxidation rxns)
others include kidney, lungs, GI tract |
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What is a microsome? What are the two important microsomes involved with oxi-red ?
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Microsomes are vesicles in hepatocytes that contain smooth ER; NADPH-cytochrome C reductase & cytochrome P-450 (cyp)
*cyp3A4 major one involved in oxidation |
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What is enzyme induction?
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Increase in cyp synthesis leading to shorterdrug 1/2 life and reduced pharmacologic activity
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What are examples of drugs that lead to enzyme induction?
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barbiturates
anticonvulsants - phenytoin Rifampin - oral contraceptives less effective |
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Can environmental sources lead to enzyme induction?
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yes; benzpyrene (smokers, charcoal grilled meat)
PCBs smokers often need more general anesthethia |
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What is the result of enzyme inhibition?
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reduced biotransformational capacity; longer 1/2 life; increased pharmacologic activity
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What causes enzyme inhibition?
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drugs
liver disease grapefruit juice |
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What is the antipyrine test? Why is it used?
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Used to determine level of hepatic function; ideal b/c it
undergoes extensive oxidative biotrans.binds poorly to albumin easily analyzed |
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increased saliva levels of antipyrine & decreased urine levels of the antipyrine metabolite would indicate what?
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decreased liver function, enzyme inhibition
e.g. space flight - reduced liver function |
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decreased salivary levels of antipyrine and increased urinary levels of the antipyrine metabolite indicate what?
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Enzyme induction
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