Pharmacokinetic True or False: Detailed Analysis and Additional Information

Here is a detailed analysis of each question in your “Pharmacokinetic True or False” section, along with additional information and notes:

1. In the same individual, the pharmacokinetics of some drugs can change with the dosage in some cases.

>> True

Note: This is especially true for drugs with non-linear pharmacokinetics. As the dosage increases, metabolizing enzymes can become saturated, leading to significant changes in the rate of drug metabolism and elimination.

2. If the hepatic clearance of a drug is close to the total clearance, the hepatic extraction ratio of the drug is higher.

>> True

Note: The extraction ratio is the proportion of drug removed from the blood as it passes through the liver. If hepatic clearance is close to total clearance, this indicates that most of the drug is eliminated via the liver, resulting in a high extraction ratio.

3. Heart failure can affect the pharmacokinetics of drugs.

>> True

Note: Heart failure can reduce blood flow to the liver, leading to reduced hepatic clearance of drugs. Additionally, heart failure can also impact drug excretion via the kidneys.

4. Non-linear pharmacokinetics only occurs in cases of enzyme saturation in the liver.

>> False

Note: Non-linear pharmacokinetics can occur due to several reasons, including:

• Enzyme saturation
• Plasma protein saturation
• Drug interactions
• Changes in liver blood flow
• Changes in renal function

5. Distribution volume of drugs in neonates.

>> Can increase, decrease, or remain unchanged

Note: The distribution volume of drugs in neonates varies depending on several factors, including:

• Age: Neonates have a higher proportion of water compared to adults, leading to increased drug distribution volume.
• Body weight: Neonates have lower body weight compared to adults, leading to decreased drug distribution volume.
• Organ development: Neonates have less developed enzyme systems compared to adults, leading to possible variations in drug distribution volume.

6. Only the pharmacokinetic parameters of drugs in the elimination phase are altered by renal insufficiency.

>> False

Note: Renal insufficiency affects both the absorption and elimination phases of a drug:

• Absorption: Renal insufficiency can affect drug absorption via the gastrointestinal tract due to reduced blood flow to the gut.
• Elimination: Renal insufficiency reduces drug clearance via the kidneys, leading to increased half-life and higher drug concentrations in the plasma.

7. Substances sensitive to displacement from binding.

>> High E, low A

Note: Displacement occurs when one drug displaces another drug bound to plasma proteins. Drugs with high protein binding (high E) are more sensitive to this phenomenon.

8. In alcoholics, drug metabolism is often decreased due to inhibition of liver enzymes.

>> False

Note: In alcoholics, drug metabolism is often increased due to induction of liver enzymes. This is because alcohol stimulates the production of drug-metabolizing enzymes, leading to increased rates of metabolism.

9. There is a positive correlation between renal clearance of a drug and creatinine clearance in the elderly.

>> True

Note: Creatinine clearance is a measure of kidney function. In the elderly, creatinine clearance is often reduced due to declining renal function, leading to reduced renal clearance of drugs.

10. Plasma drug concentration is considered the gold standard for evaluating drug efficacy.

>> False

Note: Plasma drug concentration is only one factor in evaluating drug efficacy. Drug concentrations at target tissues, binding to plasma proteins, drug metabolism and elimination also play crucial roles.

11. In patients with renal insufficiency, reduced plasma protein leads to a decrease in the volume of distribution.

>> False

Note: Renal insufficiency often leads to increased volume of distribution of drugs, not decreased. This is because reduced plasma protein levels allow the drug to distribute more freely into tissues.

12. Drugs with enterohepatic cycling have a shorter duration of action than drugs without this cycling.

>> False

Note: Drugs with enterohepatic cycling have a longer duration of action than drugs without this cycling. This is because the drug is reabsorbed multiple times via the liver and gut, increasing its residence time in the body.

13. Drugs with high molecular weight are excreted via the gastrointestinal tract.

>> False

Note: Drugs with high molecular weight are generally difficult to excrete via the gastrointestinal tract. They are often excreted via the kidneys or liver.

14. First-order drug elimination is not dependent on temperature.

>> False

Note: First-order drug elimination is dependent on temperature. Higher temperatures can increase the rate of chemical reactions, leading to increased rates of drug elimination.

15. In the two phases of enzyme metabolism, which phase has the lowest rate of metabolic reactions?

>> Methyltransferase

Note: Methyltransferase is one of the enzymes involved in phase 2 of enzyme metabolism. Phase 2 generally plays a smaller role than phase 1 in drug metabolism.

16. For a drug with a high extraction ratio, liver failure will lead to:

• Reduced metabolism
• Increased half-life
• Increased absorption volume

Note: Drugs with high extraction ratios are primarily eliminated via the liver. Liver failure reduces the hepatic clearance of the drug, leading to:

• Reduced metabolism: The liver is unable to metabolize the drug efficiently.
• Increased half-life: The drug remains in the body for a longer duration.
• Increased absorption volume: Reduced metabolism can lead to increased drug concentrations in the blood, leading to increased drug absorption volume.

17. Cirrhosis:

• Severe: Reduced blood flow, reduced function
• Moderate: Blood flow decreased, function decreased, liver volume INCREASED

Note: Cirrhosis is a chronic liver disease that can affect liver function and blood flow through the liver.

• Severe: Blood flow through the liver is significantly reduced, and liver function is severely compromised.
• Moderate: Blood flow through the liver is reduced, liver function is compromised, but liver volume can increase due to the development of fibrous tissue.

18. Drugs with high extraction ratios used in patients with renal failure require dose reduction.

>> Dose reduction is necessary

Note: Drugs with high extraction ratios are typically eliminated via the liver. Renal failure does not directly affect hepatic clearance of the drug, but dose reduction is still necessary because:

• Renal failure reduces the ability of the kidneys to excrete the drug, leading to increased drug concentrations in the plasma.
• Renal failure can alter plasma protein levels, affecting drug binding to proteins, and thereby influencing the concentration of free drug in the blood.

19. The impact of NSAIDs in pregnant women.

>> Can delay labor

Note: NSAIDs, especially in late pregnancy, can cause delayed labor by inhibiting the production of prostaglandins, a chemical involved in uterine contractions.

General Note:

• Pharmacokinetic information can vary depending on the specific drug, patient, and specific circumstances.
• Always consult with a doctor or pharmacist for accurate information relevant to your situation.
• Pharmacokinetics is a complex field. This document only provides general information and cannot replace professional medical advice.