Pharmokinetics I Flashcards Preview

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Flashcards in Pharmokinetics I Deck (25)
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1
Q

What is pharmokinetics?

A

It is the time course of a drug

2
Q

What is ADME?

A

Absorption
Distribution
Metabolism
Elimination

3
Q

What is the minimum effective concentration?

A

Min threshold required for therapeutic effect

4
Q

What is the maximum tolerated concentration?

A

Max point were the adverse effects begin to outweigh the benefits

5
Q

What is the equation for the bioavailability (F)?

A

F = AUC (oral) / AUC (IV)

6
Q

What are the uses of the AUC?

A
  • Compare clearance (CL) between individuals

- Determine the bioavailability (F)

7
Q

What types of drugs are absorbed the fastest?

A

Non-polar

8
Q

What is the problem with 2 drugs that use the same active transport carrier?

A

The process is saturable and so they will compete with each other and limit their absorption.

9
Q

What are the advantages of oral administration?

A

Many forms of the drug can be used (solution, tablets, etc)

10
Q

Wha tis the first-pass effect?

A

Some drugs become metabolized when they pass thorough the liver which makes only a fraction of the absorbed drug making it to the systemic circulation

11
Q

What is the problem with drugs and the enterohepatic circulation?

A

Drugs may be secreted into the bile and reabsorbed via the intestine. This can delay delivery to the systemic circulation and may reduce bioavailability.

12
Q

What is the salt factor?

A

The fraction of total drug that will be delivered as active drug to the systemic circulation is called the “salt factor” (S).

13
Q

What are the advantages and disadvantages of sublingual and buccal administration?

A

• Advantages:
– by-passes portal circulation and therefore avoids first pass metabolism.
– higher pH may be beneficial for absorption of more basic drugs.

• Disadvantages:
– taste and/or discomfort

14
Q

What are the advantages and disadvantages of rectal administration?

A

• Advantages:
– ~50-60% of absorbed drug by-passes portal circulation and therefore avoids first pass metabolism.
– useful in cases of nausea and vomiting.

• Disadvantages:
– discomfort, inconvenience, etc.

15
Q

What are the advantages and disadvantages of inhalation?

A

• Absorption is via passive diffusion and is facilitated by a large surface area.

16
Q

What are the advantages and disadvantages of transdermal administration?

A

• Potential benefits:
– controlled release of the drug into the patient— enables a steady blood-level profile
– user-friendly, convenient, painless, multi-day dosing—improved patient compliance
– bypassing the gastrointestinal (GI) tract obviates GI irritation that occurs with some drugs and avoids partial first-pass inactivation by the liver

• Limitations/risks:
– skin barrier limits the number of drugs that can be delivered by passive diffusion from an adhesive patch
– potential discomfort, irritation

17
Q

What are the advantages of intravenous administration?

A

• Advantages:
– greater degree of reliability and precision of administered dose
– fewer problems with absorption • not affected by food in the stomach • no “first-pass effect”

• Disadvantages:
– sight of the needle
– pain
– tissue damage and irritation – drugs must be in solution
– limited volume
18
Q

What are the advantages and disadvantages of subcutaneous administration?

A

– Advantages
• slow, even absorption
• may be used as a depot
• rate of absorption may be modified by altering blood flow

– Disadvantages
• not effective when peripheral circulation is impaired (e.g. in shock)
• limited volume

19
Q

What are the advantages and disadvantages of intramuscular administration?

A

– Advantages
• more rapid absorption than subcutaneous
• rate of absorption may be modified by altering blood flow

– Disadvantages
• potential for infection and nerve damage • risk of inadvertent i.v. administration

20
Q

What is the bolus effect?

A

Rapid injection can lead to locally exceeding the MTC which can have adverse effects

21
Q

What is the volume of distribution (Vd)?

A

Measure of how even distribution is and it is the theoretical volume of fluid where the drug would have been diluted with

22
Q

What do large Vd values indicate?

A

Indicates distribution to tissues and organs

23
Q

The antibiotic tobramycin is given to a patient with gram-negative bacteremia. The patient weight is 60 kg and the patient receives a loading dose of 1.5 mg/kg (90 mg total). If the initial plasma concentration of tobramycin is 6 mg/liter after intravenous dosing, what is the apparent volume of distribution (Vd) for this drug?

A) 10 liters 
B) 15 liters 
C) 20 liters 
D) 30 liters 
E) 60 liters
A

B.

90 mg/ (6mg/L)

= 15 L

24
Q

Theophylline is given to a patient with bronchial asthma in the emergency room. The target plasma level is 10 􏰅µg/ml and the patient weighs 50 kg. The average volume ofdistributionfor theophyllineis0.5 liters/kg. Which of the following is the correct loading dose?

A) 100 mg 
B) 250 mg 
C) 500 mg 
D) 1000 mg 
E) 2500 mg
A

B.

10 􏰅µg/ml = 0.00001 kg/L

  1. 5 L/kg = dose/0.00001 kg/L
  2. 00005 = dose/50kg
  3. 00025 kg = dose

dose = 250 mg

25
Q

What tissues can act as drug reservoirs?

A

Muscle and Fat as well as plasma proteins like albumin

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