FB - Clinical Pharmacokinetics Flashcards

1
Q

What is the primary goal of clinical pharmacokinetics in medicine?

A

Enhance drug efficacy, Reduce drug toxicity

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2
Q

What factors are considered in determining the appropriate loading dose of a drug?

A

Desired plasma drug concentration, Drug’s apparent volume of distribution

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3
Q

How does the timing of drug administration relate to trough plasma drug concentration?

A

Drugs should be administered after the trough level is reached to maintain effective concentration and minimize toxicity.

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4
Q

Why is patient age important in drug administration?

A

Age affects organ functions that impact drug metabolism and excretion, influencing drug dosage and frequency.

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5
Q

What is the significance of achieving a steady state in drug therapy?

A

Steady state indicates a balance between drug dosing and elimination, ensuring consistent therapeutic effects.

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6
Q

How does multiple dosing affect the plasma drug concentration?

A

Multiple dosing leads to drug accumulation until a steady state is reached.

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7
Q

What role does drug mechanism of action play in dosage regimen?

A

It determines how the drug interacts with the body, influencing efficacy and safety of the dosage regimen.

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8
Q

Why is patient compliance important in pharmacotherapy?

A

Non-compliance can lead to (a) suboptimal therapeutic outcomes and increased risk of drug resistance, (b) overdosing and increased drug toxicity.

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9
Q

How can drug toxicity be minimized in clinical practice?

A

By monitoring plasma drug levels and adjusting the dosage accordingly.

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10
Q

What is the importance of the apparent volume of distribution in pharmacokinetics?

A

It provides an idea where the drug is likely to be distributed in the body; helps in calculating the correct loading dose to achieve the desired drug concentration in the body.

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11
Q

How does renal function impact drug dosing and selection?

A

Renal impairment can reduce drug clearance, necessitating dosage adjustments to prevent toxicity.

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12
Q

What is the relevance of pharmacokinetic principles to personalized medicine?

A

They enable individualization of drug therapy based on patient-specific factors for optimal efficacy and safety.

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13
Q

After how many half-lives does a drug reach steady state with multiple dosing?

A

Steady state is reached after 5 half-lives (T½) of the drug.

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14
Q

How is dosing modified for drugs with different half-lives?

A

If T½ is 8-24 hours, dosing could be three to onetimes daily. If T½ is short (eg. less than 3 hours), intravenous (IV) infusion or sustained released preparations can be used.

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15
Q

For drugs with low therapeutic index (TI), what is crucial for optimum therapeutics?

A

Considerations for pharmacokinetics (PK) are more important in drugs with low TI and in patients with altered absorption, distribution, metabolism, and excretion (ADME).

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16
Q

How long does it take for plasma drug concentration (PDC) to drop to ~3% of the original level?

A

It takes 5 half-lives (T½) for PDC to drop to ~3% of the original level. (work from first principle – each half-life reduces half: 100% à 50% à 25% à 12.5% à 6.25% à 3.125%)

17
Q

How does pH affect the absorption of weak acids and bases?

A

Weak acids: Higher pH reduces absorption à high pH shifts the ionization equilibrium towards ionized species Weak bases: Higher pH increases absorption. [recall: the unionized species will be preferentially absorbed into the body]

18
Q

What are the some factors affecting drug distribution?

A

Drug’s physico-chemical properties, Biological fluid pH differences, Organ blood flow, Drug transporters, Drug-plasma protein binding

19
Q

What are some factors influence drug metabolism?

A

Enzyme activity (inhibition/induction), Pharmacogenetics (e.g., CYP2D6), Age (neonates to elderly)

20
Q

How does urine pH affect drug excretion?

A

Acidic urine: Excretes weak bases, reabsorbs weak acids. Alkaline urine: Excretes weak acids, reabsorbs weak bases.

21
Q

What does “STAT” and “PRN” mean in terms of single dosing?

A

“STAT” means immediate dosing, “PRN” means as needed.

22
Q

What is the significance of peak plasma concentration (Cmax) in steady state dosing?

A

Cmax is the highest plasma concentration of a drug after dosing, important for efficacy and determining toxicity.

23
Q

How is steady state achieved in multiple dosing?

A

Steady state is reached after 5 half-lives (T½) dosing

24
Q

How does changing dosing intervals affect drug levels?

A

Altering dosing intervals (e.g., 100mg every 2h, 3h, 6h) changes peak and trough plasma drug concentration levels.

25
Q

How is steady state concentration (Cssav) related to dosing frequency?

A

Cssav is the average plasma concentration at steady state, achieved uniformly with consistent dosing, e.g., continuous IV infusion or regular oral dosing.