Question 1

Which of the following is >90% bound to plasma proteins?

Accepted Answer

Diazepam is highly bound to plasma proteins (>90%), which means that a significant portion of the drug in the bloodstream is bound to proteins, primarily albumin, limiting its distribution into tissues. This characteristic affects its pharmacokinetics, including distribution, metabolism, and excretion.

Question 2

Which of the following has the largest volume of distribution?

Accepted Answer

Chloroquine has the largest volume of distribution among the options listed. This is because it is highly lipophilic, allowing it to extensively distribute into body tissues, including adipose tissue, which significantly increases its volume of distribution.

Question 3

Which of the following has the shortest half life?

Accepted Answer

Aspirin has the shortest half-life among the options listed, typically around 20 minutes to 2 hours, depending on various factors such as dosage and individual metabolism.

Question 4

Which of the following is a phase one reaction?

Accepted Answer

Phase one reactions involve the modification of drugs through oxidation, reduction, or hydrolysis. Reduction is a phase one reaction.

Question 5

Clearance of which drug involves capacity limited elimination?

Accepted Answer

Phenytoin exhibits capacity-limited (zero-order) elimination, meaning its rate of elimination is constant regardless of its concentration in the blood. This is because its metabolizing enzymes become saturated at therapeutic or near-therapeutic levels.

Question 6

An example of drugs that undergo chemical antagonism is

Accepted Answer

Protamine and heparin undergo chemical antagonism where protamine directly binds to heparin, neutralizing its anticoagulant effects through a direct chemical interaction.

Question 7

Regarding first order kinetics - all of the following are true EXCEPT

Accepted Answer

First order kinetics generally apply to lower, not higher, plasma concentrations of substances like ethanol. At high concentrations, zero order kinetics are more likely to apply, where the rate of metabolism is constant and independent of the drug concentration.

Question 8

Bioavailability is

Accepted Answer

Bioavailability refers to the proportion of a drug that enters the systemic circulation when introduced into the body and so is available for action or bioactivity. It is a key measure in pharmacokinetics to assess how much and how quickly a drug reaches the systemic circulation from its site of administration.

Question 9

Which of the following drugs has a high extraction ratio?

Accepted Answer

Propranolol has a high extraction ratio, meaning it is extensively metabolized by the liver during its first pass through the circulatory system. This characteristic is significant for drugs with high hepatic extraction ratios, as their bioavailability can be greatly affected by liver function and blood flow.

Question 10

Regarding biotransformation

Accepted Answer

Skin, along with the liver and other organs, is involved in drug biotransformation, indicating its role in the metabolism of substances applied topically or absorbed through the skin.

Question 11

Which of the following receptor - ligand pathway is correct?

Accepted Answer

Vitamin D functions by binding to intracellular receptors, specifically nuclear receptors, which then act as transcription factors to modulate gene expression.

Question 12

Age associated changes in pharmacokinetics include

Accepted Answer

As people age, there is a reduction in creatinine clearance due to decreased kidney function, which affects drug excretion.

Question 13

The metabolic pathway of detoxification that become increasingly important in paracetamol toxicity is

Accepted Answer

Cytochrome p450 dependent glutathione conjugation becomes increasingly important in paracetamol (acetaminophen) toxicity. This pathway helps in detoxifying the toxic metabolite NAPQI (N-acetyl-p-benzoquinone imine) produced by the cytochrome P450 system from paracetamol. When glutathione stores are depleted, this pathway is overwhelmed, leading to liver damage.

Question 14

You are given a vial with 15 ml of 0.5% prilocaine to do an arm block. How many mg of prilocaine are you injecting?

Accepted Answer

A 0.5% solution means 0.5 grams of prilocaine per 100 ml of solution. Therefore, in 15 ml, there would be 0.5 grams/100 ml * 15 ml = 0.0075 grams, which equals 7.5 grams or 75 mg of prilocaine.

Question 15

Drugs that enhance other drug metabolism include all of the following EXCEPT

Accepted Answer

Ketoconazole is a known inhibitor of cytochrome P450 enzymes, which are involved in drug metabolism. Unlike the other options listed, which can induce the enzymes and thus enhance the metabolism of other drugs, ketoconazole can actually inhibit the metabolism of other drugs, leading to increased levels of those drugs in the body.

Question 16

Which is the safest to give in pregnancy?

Accepted Answer

Heparin is considered safe during pregnancy because it does not cross the placenta and therefore does not affect the fetus. Other options like Lithium, Phenytoin, Gentamycin, and ACE inhibitors have potential risks or known adverse effects on the fetus.

Question 17

Regarding pharmacology principles

Accepted Answer

Efficacy refers to the maximum effect that can be achieved with a particular drug, regardless of dose. It is a measure of the drug's potential to achieve its desired effect.

Question 18

Reports of cardiac arrhythmias caused by unusually high blood levels of 2 antihistamines (terfenadine and astemizole) are best explained by

Accepted Answer

Terfenadine and astemizole can cause cardiac arrhythmias when their metabolism is inhibited, leading to high blood levels. Ketoconazole, a potent inhibitor of the cytochrome P450 enzyme system, can significantly increase the levels of drugs metabolized by this pathway, including terfenadine and astemizole, thus explaining the cardiac arrhythmias.

Question 19

Which of the following statements is correct?

Accepted Answer

Tobramycin is a hydrophilic antibiotic, and its distribution is primarily in the extracellular water. In conditions like oedema, where there is an increase in extracellular fluid, the volume of distribution for hydrophilic drugs like tobramycin increases. This is because the drug has more space to distribute into, leading to a lower concentration in the plasma and potentially necessitating adjustments in dosing to achieve therapeutic levels.

Question 20

Which of the following drugs has an average half life of 50 hours?

Accepted Answer

Digoxin has an average half-life of around 36 to 48 hours, which can extend up to or beyond 50 hours in patients with renal impairment, making it the closest match to the given half-life among the options.

Quiz 1: Pharmacokinetics and Drug Properties