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Questions and Answers
Which factor is NOT involved in absorption interactions according to pharmacokinetics?
Which factor is NOT involved in absorption interactions according to pharmacokinetics?
What is the primary mechanism responsible for alteration in distribution interactions?
What is the primary mechanism responsible for alteration in distribution interactions?
Which of the following drugs is likely to be affected by antibiotics through gut microflora alteration?
Which of the following drugs is likely to be affected by antibiotics through gut microflora alteration?
Which drug combination is associated with an increased risk of hemorrhage due to displacement interactions?
Which drug combination is associated with an increased risk of hemorrhage due to displacement interactions?
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What effect does a rapid gastric emptying have on the absorption of drugs?
What effect does a rapid gastric emptying have on the absorption of drugs?
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Which element significantly influences absorption interactions by forming poorly soluble and unabsorbable complexes?
Which element significantly influences absorption interactions by forming poorly soluble and unabsorbable complexes?
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Which of the following conditions is a type of absorption interaction?
Which of the following conditions is a type of absorption interaction?
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Which drug is primarily affected by anti-cholinergic agents through delayed gastric emptying?
Which drug is primarily affected by anti-cholinergic agents through delayed gastric emptying?
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What is the primary genetic cause for sensitivity to suxamethonium?
What is the primary genetic cause for sensitivity to suxamethonium?
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Which enzyme activity is primarily responsible for the classification of individuals as fast or slow acetylators?
Which enzyme activity is primarily responsible for the classification of individuals as fast or slow acetylators?
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How do slow acetylators influence drug therapy?
How do slow acetylators influence drug therapy?
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What type of toxicity is associated with isoniazid in slow acetylators?
What type of toxicity is associated with isoniazid in slow acetylators?
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What may fast acetylators require due to their drug metabolism characteristics?
What may fast acetylators require due to their drug metabolism characteristics?
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What is the primary outcome of enzyme induction in metabolism interactions?
What is the primary outcome of enzyme induction in metabolism interactions?
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Which of the following drugs is least likely to cause enzyme inhibition?
Which of the following drugs is least likely to cause enzyme inhibition?
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Which mechanism does NOT typically contribute to excretion interactions?
Which mechanism does NOT typically contribute to excretion interactions?
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How does the presence of antacids affect the reabsorption of basic drugs?
How does the presence of antacids affect the reabsorption of basic drugs?
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What is a common consequence of enzyme inhibition in drug interactions?
What is a common consequence of enzyme inhibition in drug interactions?
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Which drug is associated with increased levels of acetaldehyde due to enzyme interaction?
Which drug is associated with increased levels of acetaldehyde due to enzyme interaction?
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In which scenario would renal clearance of lithium decrease, posing a risk of toxicity?
In which scenario would renal clearance of lithium decrease, posing a risk of toxicity?
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Which mechanism is primarily involved in the increase of plasma levels of acidic drugs when using probenecid?
Which mechanism is primarily involved in the increase of plasma levels of acidic drugs when using probenecid?
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Which of the following enzymes is noted to have low activity in neonates?
Which of the following enzymes is noted to have low activity in neonates?
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In elderly patients, which drug class is more likely to cause confusion rather than sedation?
In elderly patients, which drug class is more likely to cause confusion rather than sedation?
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Which of the following factors is NOT influenced by pregnancy affecting drug pharmacokinetics?
Which of the following factors is NOT influenced by pregnancy affecting drug pharmacokinetics?
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Which condition is associated with increased sensitivity to several drugs due to pharmacokinetic variations?
Which condition is associated with increased sensitivity to several drugs due to pharmacokinetic variations?
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Which drug is mentioned as having increased sensitivity due to an autoimmune condition?
Which drug is mentioned as having increased sensitivity due to an autoimmune condition?
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Which type of drugs is more likely to transfer quickly across the placental barrier?
Which type of drugs is more likely to transfer quickly across the placental barrier?
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Which factor contributes to variations in drug effects due to genetic makeup?
Which factor contributes to variations in drug effects due to genetic makeup?
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Which of the following is NOT a mechanism by which drug interactions can occur?
Which of the following is NOT a mechanism by which drug interactions can occur?
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What defines direct pharmacodynamics interactions between drugs?
What defines direct pharmacodynamics interactions between drugs?
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Which of the following is an example of antagonism in drug interactions?
Which of the following is an example of antagonism in drug interactions?
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What is synergy or potentiation in drug interactions?
What is synergy or potentiation in drug interactions?
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Which statement correctly describes indirect pharmacodynamics interactions?
Which statement correctly describes indirect pharmacodynamics interactions?
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How does individual diversity influence drug interactions?
How does individual diversity influence drug interactions?
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What physiological factor contributes to increased drug effects in older adults?
What physiological factor contributes to increased drug effects in older adults?
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Which factor is NOT considered part of the individual diversity affecting drug interactions?
Which factor is NOT considered part of the individual diversity affecting drug interactions?
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What potential outcome can occur from salicylates in the presence of warfarin?
What potential outcome can occur from salicylates in the presence of warfarin?
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Study Notes
Pharmacokinetic Interactions
- Absorption interactions can be caused by complexation, adsorption, alteration of GI pH, gut motility, gut microflora, and malabsorption syndrome.
- Antacids, food, and mineral supplements containing aluminum, magnesium, iron, zinc, and calcium ions can cause complexation and adsorption of drugs like cephrofloxacine and pencillamine, reducing their absorption.
- Antacids may increase the dissolution and absorption of drugs like sulfonamides or ferrous sulfate but decrease absorption of drugs like aspirin.
- Metoclopramide can increase absorption of drugs like aspirin, diazepam, levodopa, and mexiletine by increasing gastric emptying.
- Anticholinergics can delay gastric emptying and decrease the absorption of drugs like levodopa, lithium carbonate, and mexiletine.
- Antibiotics can destroy gut flora, which inactivates drugs like digoxin in the lower intestine.
- Neomycin can inhibit the absorption of vitamins A and B12, and digoxin.
Distribution Interactions
- The most important mechanism for distribution interaction is the alteration of plasma protein (PP)-drug binding.
- Competitive displacement interactions can occur when certain drugs displace other drugs bound to PP, increasing their free concentration and potentially causing adverse effects.
- Phenylbutazone and chloral hydrate can displace anticoagulants from PP, increasing the risk of hemorrhage.
- Sulphonamides can displace tolbutamide from PP, increasing its hypoglycemic effect.
Metabolism Interactions
- Enzyme induction increases the rate of drug metabolism, leading to faster elimination and potentially lower efficacy of the drug.
- Enzyme inhibition decreases the rate of drug metabolism, prolonging drug action and potentially leading to drug accumulation and toxicity.
- Corticosteroids, oral contraceptives, coumarins, and phenytoin can induce enzyme activity, decreasing plasma levels of drugs like anti-TB antibiotics.
- Rifampicin can induce enzyme activity, decreasing plasma levels of oral contraceptives and oral hypoglycemics.
- MAO inhibitors can inhibit enzyme activity, increasing unmetabolized tyramine levels and potentially causing hypertensive crisis.
- Metronidazole can inhibit enzyme activity, increasing the anticoagulant activity of coumarins.
- Phenylbutazone can inhibit enzyme activity, increasing plasma acetaldehyde levels after alcohol consumption.
Excretion Interactions
- Alteration in renal blood flow, urine pH, competition for active secretion, and forced diuresis are common mechanisms for excretion interactions.
- Probenecid can inhibit the active tubular secretion of acidic drugs like penicillin, cephalosporins, and nalidixic acid, increasing their plasma levels.
- Antacids, thiazide ACE inhibitors, and acetazolamide can increase urine pH, increasing passive reabsorption of basic drugs and increased risk of toxicity.
- NSAID's can decrease renal blood flow, decreasing lithium clearance and increasing the risk of toxicity.
Pharmacodynamic Interactions
- Pharmacodynamic interactions can be direct or indirect.
- Direct interactions occur when drugs with similar or opposite pharmacological effects are used simultaneously.
- Antagonism occurs when interacting drugs have opposing actions.
- Addition or summation occurs when drugs have similar actions, and the resulting effect is the sum of the individual effects.
- Synergism or potentiation occurs when one drug enhances the action of another.
- Indirect interactions occur when drugs have unrelated effects but can interact in unintended ways.
Individual and Interindividual Diversity
- Individual diversity in drug response can be influenced by factors like ethnicity, age, pregnancy, breastfeeding, disease, and genetic factors.
- African-American patients with heart failure may respond differently to hydralazine and nitrates compared to white Americans.
- Chinese individuals metabolize ethanol differently than Europeans, leading to higher acetaldehyde levels and potential side effects like flushing and palpitations.
Age and Drug Interactions
- Drug effects can be greater and more prolonged at the extremes of life.
- Elderly individuals may experience more pronounced drug effects due to changes in body composition, distribution volume, and enzyme activity.
- Several important enzymes like hepatic microsomal oxidase, glucuronyltransferase, acetyltransferase, and plasma esterases have lower activity in neonates and gradually decline with age.
- Benzodiazepines may produce more confusion and less sedation in elderly individuals compared to young people.
- Hypotensive drugs may cause postural hypotension more commonly in elderly individuals.
Pregnancy
- Maternal plasma albumin concentration is reduced during pregnancy, influencing drug protein binding.
- Cardiac output is increased during pregnancy, increasing renal blood flow and renal elimination of drugs.
- Lipophilic molecules cross the placental barrier rapidly, while hydrophobic drugs transfer slowly.
- Some drugs are excluded by the placental barrier, while others are transferred to the fetus and eliminated at a slower rate than in the mother.
Disease
- Disease can influence drug pharmacokinetics and pharmacodynamics, leading to variations in drug concentration and response.
- Hypothyroidism is associated with increased sensitivity to drugs like pethidine.
- Myasthenia gravis, an autoimmune disease affecting acetylcholine receptors, increases sensitivity to neuromuscular blocking agents like vecuronium.
Pharmacogenetics and Drug Effects
- Genetic variations can influence drug metabolism and affect drug response.
- Deficiencies in glucose 6-phosphate dehydrogenase (G6PD) can cause resistance to malaria.
- Genetic variations in the rate of suxamethonium metabolism can lead to prolonged neuromuscular block.
Fast Acetylators and Slow Acetylators
- Individuals can be classified as fast or slow acetylators based on their ability to metabolize certain drugs, specifically acetylated compounds.
- Fast acetylators metabolize drugs quickly due to higher activity of the NAT2 enzyme, leading to faster clearance and potentially lower drug efficacy.
- Slow acetylators metabolize drugs more slowly due to lower activity of the NAT2 enzyme, leading to prolonged drug exposure and potential toxicity.
- Variations in acetylator status are important for drug therapy, particularly with medications like isoniazid.
- Isoniazid can cause peripheral neuropathy in slow acetylators and hepatotoxicity in fast acetylators..
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Description
Test your knowledge on pharmacokinetic interactions, focusing on absorption and distribution of drugs. Explore how various factors such as antacids and gut microflora influence drug effectiveness and absorption rates. This quiz will challenge your understanding of complex mechanisms in pharmacology.
