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Questions and Answers
What determines the necessity, route, and extent of metabolism?
What determines the necessity, route, and extent of metabolism?
- Chemical structure of the drug (correct)
- Type of metabolic enzyme
- Drug dosage
- Physiologic or disease state
What happens to drug concentrations when the drug dosage is increased?
What happens to drug concentrations when the drug dosage is increased?
- They decrease
- They become unpredictable
- They increase (correct)
- They remain the same
What can be affected by pathologic factors that alter liver function?
What can be affected by pathologic factors that alter liver function?
- Hepatic clearance (correct)
- Cardiac output
- Metabolic enzyme activity
- Renal clearance
What is a result of congestive heart failure?
What is a result of congestive heart failure?
What is a factor that influences drug metabolism?
What is a factor that influences drug metabolism?
What can be saturated by increased drug concentrations?
What can be saturated by increased drug concentrations?
What happens to the fraction of unbound drug when albumin production decreases?
What happens to the fraction of unbound drug when albumin production decreases?
What determines the acetylation rate?
What determines the acetylation rate?
Who is more prone to hepatoxicity from isoniazid?
Who is more prone to hepatoxicity from isoniazid?
What is the effect of a low protein diet on oxidative drug metabolism capacity?
What is the effect of a low protein diet on oxidative drug metabolism capacity?
What can lead to a deficiency of certain amino acids?
What can lead to a deficiency of certain amino acids?
What can affect the fraction of unbound drug?
What can affect the fraction of unbound drug?
What is the primary function of esterases in plasma?
What is the primary function of esterases in plasma?
Where does the first-pass metabolism of drugs administered intravenously occur?
Where does the first-pass metabolism of drugs administered intravenously occur?
What is the primary function of nasal mucosa in drug metabolism?
What is the primary function of nasal mucosa in drug metabolism?
What is the primary function of placental metabolism?
What is the primary function of placental metabolism?
What is a strategy to manage drug metabolism?
What is a strategy to manage drug metabolism?
What is a site of extrahepatic metabolism?
What is a site of extrahepatic metabolism?
What is a portal of entry for drugs?
What is a portal of entry for drugs?
What is a portal of excretion for drugs?
What is a portal of excretion for drugs?
Where are drug receptors typically located?
Where are drug receptors typically located?
What is the primary function of a drug receptor?
What is the primary function of a drug receptor?
What is another term for drug receptor interactions?
What is another term for drug receptor interactions?
What is the significance of specific regions on a receptor?
What is the significance of specific regions on a receptor?
What is the term for a molecule that binds to a receptor?
What is the term for a molecule that binds to a receptor?
What is the primary mechanism by which receptors are activated?
What is the primary mechanism by which receptors are activated?
What is the primary purpose of administering carbidopa along with levodopa?
What is the primary purpose of administering carbidopa along with levodopa?
Which enzyme is primarily responsible for the Phase I metabolism of drugs?
Which enzyme is primarily responsible for the Phase I metabolism of drugs?
What mechanism do beta-lactamase inhibitors utilize to combat antibiotic resistance?
What mechanism do beta-lactamase inhibitors utilize to combat antibiotic resistance?
Which of the following is an example of a Phase II metabolism enzyme?
Which of the following is an example of a Phase II metabolism enzyme?
Which component is not typically involved in the metabolism of levodopa?
Which component is not typically involved in the metabolism of levodopa?
Which of the following statements about beta-lactam antibiotics is incorrect?
Which of the following statements about beta-lactam antibiotics is incorrect?
What function does glucuronyl transferase serve in drug metabolism?
What function does glucuronyl transferase serve in drug metabolism?
Why is it important to block peripheral metabolism of levodopa?
Why is it important to block peripheral metabolism of levodopa?
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Study Notes
Drug Receptors
- A protein molecule embedded in the cell membrane with part of its structure exposed on the outside of the cell, where the drug exerts its characteristic effects.
- Contains specific regions that react with complementary functional groups.
- Also referred to as Ligand-Receptor Interactions.
Receptor Activation
- The process by which receptors are activated, leading to a response.
Factors Influencing Drug Metabolism
- Chemical structure: the presence or absence of functional groups determines the necessity, route, and extent of metabolism.
- Drug dosage: increased dosage can saturate metabolic enzymes, leading to increased drug concentrations.
- Physiologic or disease state: pathologic factors that alter liver function can affect a drug's hepatic clearance.
- Genetic variation: acetylation rate depends on the amount of N-acetyltransferase present.
- Nutritional status: low protein diet can lead to deficiency of certain amino acids, decreasing oxidative drug metabolism capacity.
Metabolism Sites
- Liver: primary site of drug metabolism.
- Plasma: contains esterases responsible for hydrolysis of esters.
- Intestinal mucosa: lipid-soluble drugs are metabolized into polar or inactive metabolites before entering the blood.
- Nasal mucosa: provides a high level of CYP450 activity, altering the amount of drug that reaches the systemic circulation.
- Lung: responsible for first-pass metabolism of drugs administered intravenously, intramuscularly, transdermally, or subcutaneously.
- Placenta and fetus: drugs in their active form in the maternal circulation pass unchanged into the fetal circulation.
Strategies to Manage Drug Metabolism
- Pharmaceutical strategies: involve the use of different dosage forms to either avoid or compensate for rapid metabolism.
- Decreasing the overall extent of metabolism and increasing the duration of action.
Examples of Strategies to Manage Drug Metabolism
- Levodopa: concurrent administration of carbidopa prevents peripheral formation of dopamine, ensuring adequate concentrations of L-dopa reach the CNS.
- Beta-lactam antibiotics: beta-lactamase inhibitor (clavulinic acid) is used in conjunction with a penicillin (amoxicillin) to treat infections.
Enzymes Catalyzing Phase I Metabolism
- Cytochrome P-450
- Aldehyde and alcohol dehydrogenase
- Deaminases
- Esterases
- Amidases
- Epoxide hydratases
Enzymes Catalyzing Phase II Metabolism
- Glucuronyl transferase (glucuronide conjugation)
- Sulfotransferase (sulfate conjugation)
- Transacylases (amino acid conjugation)
- Acetylases
- Ethylases
- Methylases
- Glutathione transferase
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