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Questions and Answers
What effect does quinidine have on tubular reabsorption?
What effect does quinidine have on tubular reabsorption?
- Has no effect on passive reabsorption
- Decreases passive reabsorption
- Increases active reabsorption
- Increases passive reabsorption (correct)
What happens to the plasma levels of acidic drugs when Probenecid is administered with Quinolones?
What happens to the plasma levels of acidic drugs when Probenecid is administered with Quinolones?
- They decrease due to enhanced excretion
- They fluctuate randomly
- They remain unchanged
- They increase due to inhibition of organic anion transporters (correct)
What type of interaction occurs when two drugs compete for the same active transport system in the renal tubules?
What type of interaction occurs when two drugs compete for the same active transport system in the renal tubules?
- Transporter protein interaction (correct)
- Drug binding interaction
- Pharmacokinetic interaction
- Pharmacodynamic interaction
What is the effect of aspirin on tubular reabsorption?
What is the effect of aspirin on tubular reabsorption?
What type of interaction alters the pharmacodynamics profile of a drug?
What type of interaction alters the pharmacodynamics profile of a drug?
What is the primary mechanism of quinidine's effect on tubular reabsorption?
What is the primary mechanism of quinidine's effect on tubular reabsorption?
What is the mechanism by which verapamil increases digoxin absorption?
What is the mechanism by which verapamil increases digoxin absorption?
What is the effect of a basic environment on the absorption of a weak acid?
What is the effect of a basic environment on the absorption of a weak acid?
What is the effect of salicylates on warfarin?
What is the effect of salicylates on warfarin?
Which enzyme is responsible for the metabolism of 40% of drugs?
Which enzyme is responsible for the metabolism of 40% of drugs?
Which of the following drugs can decrease the absorption of ketoconazole by increasing the pH of the gut?
Which of the following drugs can decrease the absorption of ketoconazole by increasing the pH of the gut?
What is the effect of enzyme induction on the activity of co-administered drugs?
What is the effect of enzyme induction on the activity of co-administered drugs?
What is the mechanism of interaction between antacids and tetracycline?
What is the mechanism of interaction between antacids and tetracycline?
What is the time frame for enzyme induction to develop and wear off?
What is the time frame for enzyme induction to develop and wear off?
Which of the following drugs can increase the rate of gastric emptying and absorption of paracetamol?
Which of the following drugs can increase the rate of gastric emptying and absorption of paracetamol?
What is the effect of rifampin on the absorption of digoxin?
What is the effect of rifampin on the absorption of digoxin?
Which of the following drugs is an example of an enzyme inducer?
Which of the following drugs is an example of an enzyme inducer?
Which of the following is an example of a pH-dependent absorption interaction?
Which of the following is an example of a pH-dependent absorption interaction?
What is the effect of anticholinergics on the absorption of drugs?
What is the effect of anticholinergics on the absorption of drugs?
Which of the following interactions involves the inhibition of a drug transporter protein?
Which of the following interactions involves the inhibition of a drug transporter protein?
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Study Notes
Pharmacokinetic Interactions
- Quinidine increases the risk of toxicity by increasing tubular passive reabsorption of the object drug.
- Aspirin decreases the clearance of the object drug by decreasing tubular passive reabsorption.
- Drugs that use the same active transport systems in the renal tubules can compete with each other for excretion.
Changes in Active Renal Tubular Excretion
- Penicillins, Cephalosporins, and Quinolones can inhibit organic anion transporters (OATS), increasing the plasma levels of acidic drugs and potentially causing toxicity.
- Probenecid can inhibit the excretion of acidic drugs, leading to increased plasma levels and potential toxicity.
Pharmacodynamic Interactions
- Verapamil can increase digoxin absorption by inhibiting P-glycoprotein.
Distribution Interactions
- Salicylates and Sulfonamides can displace warfarin from its binding sites, increasing the risk of hemorrhage.
- Protein-binding interactions can occur when one drug competes with another for binding sites, depending on concentrations and affinities.
Metabolism Interactions
- Enzyme induction can increase the activity of metabolizing enzymes, leading to increased metabolism of certain co-administered drugs.
- Cytochrome P450 isoenzymes, particularly CYP3A4, are responsible for the metabolism of many drugs.
- Enzyme induction may take up to 3 weeks to develop and wear off.
- Examples of enzyme-inducing drugs include Phenobarbitone, Phenytoin, Carbamazepine, and Rifampicin.
Changes in Gl pH
- Weak bases are more absorbable in basic environments.
- Weak acids are more absorbable in acidic environments.
- Antacids, Hâ‚‚-receptor antagonists, and Proton pump inhibitors can decrease the absorption of ketoconazole by increasing the pH.
Adsorption, Chelation, and Other Complexing Mechanisms
- Antacids and mineral supplements can decrease the absorption of tetracycline and ciprofloxacin by forming less soluble chelates.
Changes in Gut Motility
- Anticholinergics agents can delay gastric emptying, decreasing the rate of drug absorption.
- Prokinetic agents can increase gastric emptying, increasing the rate of drug absorption.
- Propantheline can delay gastric emptying, decreasing the rate of absorption of paracetamol.
- Metoclopramide and domperidone can increase gastric emptying, increasing the rate of absorption of paracetamol.
Inhibition or Induction of Drug Transporter Proteins
- Rifampin can decrease digoxin absorption by inducing P-glycoprotein.
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