Podcast
Questions and Answers
What is the primary reason for drug metabolism?
What is the primary reason for drug metabolism?
- To decrease the absorption of the drug
- To increase the activity of the drug
- To convert the drug to a more polar metabolite for easy excretion (correct)
- To increase the distribution of the drug
What type of reaction is responsible for the conversion of enalapril to enalaprilat?
What type of reaction is responsible for the conversion of enalapril to enalaprilat?
- Phase I reaction (correct)
- Phase II reaction
- Non-synthetic reaction
- Synthetic reaction
Which of the following is an example of a drug that is converted to a toxic metabolite?
Which of the following is an example of a drug that is converted to a toxic metabolite?
- Paracetamol (correct)
- Prednisone
- Diazepam
- Enalapril
What is the effect of renal disease on pharmacokinetics?
What is the effect of renal disease on pharmacokinetics?
What is the role of genetic variability in drug metabolism?
What is the role of genetic variability in drug metabolism?
What is the primary difference between Phase I and Phase II reactions?
What is the primary difference between Phase I and Phase II reactions?
What is the effect of an enzyme inducer on pharmacokinetics?
What is the effect of an enzyme inducer on pharmacokinetics?
What is the primary location of drug metabolism?
What is the primary location of drug metabolism?
What is the primary function of the glucuronyl transferase enzyme system?
What is the primary function of the glucuronyl transferase enzyme system?
What is the result of enzyme induction on the metabolism of a drug?
What is the result of enzyme induction on the metabolism of a drug?
Which of the following is a characteristic of microsomal enzymes?
Which of the following is a characteristic of microsomal enzymes?
What is the effect of liver cell failure on biotransformation?
What is the effect of liver cell failure on biotransformation?
What is the primary function of cytochrome P450 enzymes?
What is the primary function of cytochrome P450 enzymes?
Which of the following is an example of a Phase II reaction?
Which of the following is an example of a Phase II reaction?
What is the effect of pharmacogenetic variations on biotransformation?
What is the effect of pharmacogenetic variations on biotransformation?
What is the result of enzyme inhibition on the metabolism of a drug?
What is the result of enzyme inhibition on the metabolism of a drug?
What is the consequence of enzyme induction on the metabolism of other drugs?
What is the consequence of enzyme induction on the metabolism of other drugs?
What is the effect of phenobarbitone on the elimination of bilirubin in neonatal jaundice?
What is the effect of phenobarbitone on the elimination of bilirubin in neonatal jaundice?
What is the clinical value of enzyme inhibition?
What is the clinical value of enzyme inhibition?
What is the consequence of rifampicin on the metabolism of oral contraceptives?
What is the consequence of rifampicin on the metabolism of oral contraceptives?
What is the effect of erythromycin on the metabolism of theophylline?
What is the effect of erythromycin on the metabolism of theophylline?
What is the primary route of excretion for most drugs?
What is the primary route of excretion for most drugs?
What is the consequence of enzyme inhibition on the metabolism of warfarin?
What is the consequence of enzyme inhibition on the metabolism of warfarin?
What is the mechanism of overcoming the effects of enzyme induction?
What is the mechanism of overcoming the effects of enzyme induction?
Study Notes
Drug Metabolism (Biotransformation)
- Occurs mainly in the liver and also in other organs, such as the intestinal lumen or wall, lung, plasma, skin, and kidney
- The main aim is to convert the drug to a more polar (ionized) metabolite, which is easily excreted
Phase I Reactions
- Include oxidation, reduction, and hydrolysis
- Result in an inactive polar metabolite
- Examples: glucuronic acid, glycine, glutathione, and sulfate conjugation
Phase II Reactions
- Include glucuronyl transferase and sulfate conjugation
- Result in an inactive polar conjugate
- Examples: glucuronyl transferase and sulfate conjugation
Enzyme Induction
- Certain drugs stimulate the activity and amount of microsomal enzyme systems responsible for metabolism
- Reversible, occurs over a few days, and passes off over 2-3 weeks after withdrawal of the inducer
- Examples of enzyme inducers: phenobarbitone, phenytoin, carbamazepine, rifampicin, and nicotine
- Clinical value:
- Increase its own metabolism (→ tolerance)
- Increase the metabolism of other drugs metabolized by these enzymes
- Increase metabolism of endogenous substrates
Enzyme Inhibition
- Certain drugs inhibit the microsomal enzyme systems, leading to a decrease in their activity
- Reversible, occurs over a few days, and passes off over 2-3 weeks after withdrawal of the inhibitor
- Examples of enzyme inhibitors: chloramphenicol, erythromycin, ciprofloxacin, and valproate
- Clinical value: ↓ metabolism of drugs given simultaneously → ↑ level → risk of toxicity
Drug Excretion
- The kidney is the most important route of excretion
- Other sites for drug excretion:
- Lungs (e.g., volatile anesthetics)
- Saliva (e.g., iodides)
- Bile (e.g., rifampicin)
Factors Affecting Biotransformation
- Physiological changes in metabolizing activity due to age and sex
- Pathological factors affecting hepatic activity (e.g., liver cell failure)
- Pharmacogenetic variations in metabolizing enzymes
- Enzyme induction and enzyme inhibition
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Description
This quiz covers the process of drug metabolism, including the conversion of non-polar metabolites to polar conjugates, making them more soluble and easier to eliminate. It also covers the enzymes involved in this process, such as cytochrome P450 and glucuronyl transferase.
