Intro 2 Pharmacokinetics Flashcards
(74 cards)
1
Q
Define Pharmacology
A
study of interactions of chemicals within living systems
2
Q
Define Medical pharmacology
A
science of substances used to prevent, diagnose, and treat disease
3
Q
Define Drug
A
any substance that brings about a change in biologic function through its chemical actions
4
Q
Define Receptor
A
the molecular components of the body with which a drug interacts to bring about its effects
5
Q
a) What are the 3 types of receptor bonds and b) name an example of each?
A
- Covalent, Electrostsatic, and Other
- Covalent bonds: very strong, usually irreversible
- Electrostatic bonds: weaker bonds
- Other bonds (very weak): hydrogen bonding, etc.
6
Q
Define Pharmacokinetics
A
Actions of the body on a drug
7
Q
What are the 4 actions of the body on a drug?
A
Absorption, Distribution, Metabolism, and Elimination
8
Q
Define Pharmacodynamics
A
Actions of the body on a drug
what reaction specific drugs have on the body
9
Q
What are the major routes of administration for medications and describe each.
A
Parenteral, Enteral, and Other
- Parenteral: Doesn’t utalize GI
- Enteral: Utalizes GI
- Other
10
Q
Name the 3 major Parenteral routes
A
IV, IM, and SC
11
Q
What are the advantages of Parenteral administration (IV, IM, SC)?
A
- Rapid onset of action
- avoidance of harsh GI envt
- can be utilized in unconscious
12
Q
What are the disadvantages of Parenteral administration (IV, IM, SC)
A
- Overdoses can’t be as readily treated
- pain/fear associated w/ administration
- higher infection risk
13
Q
What are the risks associated with IV injection?
A
- Infections through contamination at injection site
- Hemolysis
- Pain/injection site reaction
14
Q
Describe the absorption of IM administration
A
- Requires absorption from site of administration by avoids GI tract & 1st pass
- Drugs in aqueous solutions–> rapid absorption
- Depot formulations (non-aqueous)–> slow absorption/sustained release
15
Q
Describe SQ administration
A
- requires absorption from administration site
- slower than IV
- minimizes some risks associated with IV administration
16
Q
What are the advantages of Oral (PO) administration?
A
- Easy to administer
- Minimizes risk of systemic infections
- Overdoses can potentially be treated
17
Q
What are the disadvantages of PO administration?
A
- Complicated drug absorption pathways with 1st pass effect
- Acidic GI envirnoment
- Absorption is influenced by food intake or other drugs
18
Q
Describe Sublingual (SL) administration
A
Placement of drug under tongue, which allows for direct diffusion into systemic circulation
19
Q
What are the advantages of SL administration?
A
- Convenient administration -rapid absorption
- low risk of infection
- Avoidance of harsh GI environment & 1st pass effect
20
Q
What are the advantages of Rectal (PR) administration?
A
- Prevents destruction of drugs by harsh GI
- Lower rates of biotransformation from the liver than PO
- Useful in emesis (vomiting)
- Useful in unconsciousness or actively seizing pts.
21
Q
What are the disadvantages of PR administration
A
- Discomfort
- Drugs can cause irritation/inflammation of rectal mucosa
- Absorption greatly varies
22
Q
Describe inhalation administration
A
- Effective for respiratory conditions due to direct delivery to the site of action
- delivery to large surface
- used for gases
- minimization of systemic side effects
23
Q
Describe intranasal administration
A
Absorbed for local effects or systemic effects
24
Q
Describe intrathecala administration (space under membrane of brain or sc)
A
- Direct administration into CSF
- Useful in treating meningitis
25
Describe topical administration
- Mostly reserved for local effects of drugs
| - Applied to skin, eyes, etc.
26
Describe transdermal administration (ex patch)
- Systemic effect by application of drug to the skin
- Varying rate of absorption based on skin condition at the site of application
- used for sustained delivery of drugs
27
Define absorption
The transfer of a drug from its site of administration to the blood stream
28
Name the factors that affect absorption
```
Solubility
Concentration
Blood flow
Surface area
Contact time
pH
```
29
Name the mechanisms of absorption
Passive diffusion, Facilitated diffusion, active transport, and endocytosis
30
Describe how concentration affects absorption
High concentrations of a drug lead to more absorption than low concentrations of a drug
31
Describe how blood flow affects absorption
Greater blood flow leads to higher rates of absorption
32
Describe how surface area affects absorption
More surface area for absorption leads to more rapid absorption (ie. lungs, intestine)
33
Describe how contact time affects absorption
The greater the contact time, the greater the absorption
34
Describe how pH affects absorption
pH directly determines the amount of ionized vs. unionized (which affects solubility)
-only ionized (no charge) forms can cross cell membranes
35
What donates a proton to form anions?
Weak acids
36
What accepts a proton to form cations?
Weak bases
37
What is the Henderson-Hasselbalch used to determine?
The ratio of ionized to unionized
38
How is a pka value linked to an acid?
The lower the pKa value, the stronger the acid
39
Define Bioavaliability (F)
Fraction of unchanged drug reaching the systemic circulation following administration
40
What is the bioavaliability (f) of an IV injection?
100%
41
What does the bioavaliability of an PO medication depend on?
Absorption (rate/extent) and Metabolism (1st pass effect)
42
Describe the 1st pass effect
- After absorption, portal blood takes the drug to the liver before entering the circulation
- When passing through the liver, the drug may be metabolized/inactivated, or excreted into bile--> less active drug makes it to systemic circulation
43
What formula is used to determine bioavaliability?
F = f x (1-ER)
(f)=extent of absorption (ER)=extraction ratio .
44
Define distribution
Delivery of a drug from the systemic circulation to target tissues
45
What are the major determinants of drug distribution?
- Blood flow
- Capillary permeability & Blood brain barrier
- Drug structure,properties/ characteristics
- Protein binding
46
How does blood flow affect distribution?
Greater blood flow leads to faster distribution of drug
47
Name high flow and low flow areas of distribution in the body
(high flow) brain, liver, kidney
| (low flow) adipose tissue
48
Define capillary permeability
Capacity for drug molecules to pass through capillary walls
49
What type of capillary permeability does the Brain have?
continuous capillary structure (does not allow drugs through)
50
Describe the mechanisms of the BBB
(Lipid soluble)
-Dissolve in membrane of endothelial cells
(Specific transporters)
-Carry the drug through the membrane of endothelial cells
51
Left off on distribution factors slide 33; also revisit question 7: Describe transport mechanisms of a drug from the site of administration to the site of action.
go back
52
Define volume of distribution (Vd)
Distribution of drug within the fluid compartments of the body
(tells how much blood is in the body as opposed to the blood)
53
*How much body water is located intracellularly?
2/3
54
*How much body water is located extracellularly?
1/3
55
*How much body water is located intravascular (IV)?
1/4
56
*How much body water is located interstitial (IS)?
3/4
57
What percentage of the body is composed of water?
60%
58
* What formula is used to calculate volume of distribution?
Vd = D/ C
- D: total amount of drug in body
- C: plasma concentration of drug
59
*What does a small Vd indicate?
The drug is primarily in the plasma
60
*What does a high Vd indicate?
A high concentration of a drug in the extravascular space (in tissues)
61
* What formula would you use to approximate how much drug is needed to achieve the appropriate concentration level based on current plasma level?
(Vd) (C2-C1)
- C1 = Current plasma concentration
- C2 = Desired plasma concentration
62
What occurs when a protein binds to a drug?
The protein renders the bound drug inactive
63
* What type of protein binding is reversible?
Binding to albumin
64
* What occurs in protein binding competition?
2 different drugs have a high affinity for abumin and they compete for the binding site
65
* You have a patient who is currently taking a drug (D1) that is protein bound. Another protein-bound drug is added (D2). What will occur?
- D1 will be displaced from binding sites by D2
- Toxicity may occur with D1 since the displaced drug (D1) has become activitated
- Toxicity may occur with D2 since there is a higher fraction of free drug and no available binding sites
66
*You have a patient who is taking D1 and D2 (both protein bound). What will happen if D1 is discontinued?
- Once D1 is eliminated, D2 will have more avaliable protein binding sites
- D2 will become protein bound, and thus inactive
- Sub-therapeutic levels of D2 may occur
67
What occurs during distribution?
The drug may initially be distributed to one area and then redistributed to another
68
How might inflamed meninges alter distribution?
They may increase the distribution of drugs in the CSF with meningitis
69
What affect might inflammation/infection have on distribution?
- A layer of WBC and fluid from edema may lead to decreased drug distribution to infected area
- inflammation may increase blood flow due to inflammatory response and increased distribution to the affected tissues
70
*Which route of administration typically has the quickest onset of action (effect)?
Intravenous
71
*What route of administration is LEAST desirable for a drug that is not stable in an acidic environment?
Oral
72
*What mechanism of absorption is capable of moving drugs against a concentration gradient?
Active Transport
73
*A patient taking two highly protein-bound drugs abruptly stops taking one of them. The therapeutic effect of the continued drug would be expected to
Decrease (because the drug is now available for binding to a protein; if the drug binds to a protein it would become inactive and decrease the therapeutic effects)
74
*Estimate the oral bioavailability of a drug that is 100% absorbed and has an extraction ratio of 0.25
F =f x (1-ER) = 100 x (1-25)=
| 75%
