Module 6 Pharmacokinetics Flashcards
(35 cards)
1
Q
Clinical Pharmacokinetics
A
- Relationship between drug effects & concentration
- Quantitative relationship between dose & effect
- Framework for measurements of drug concentration within body fluids
2
Q
Drug Disposition Parameters
A
- Clearance, efficiency of elimination
- Volume of distribution (apparent space)
- Elimination of half life (rate of removal)
- Bioavailability (fraction in systematic circulation)
3
Q
Drug Therapy Goal
A
- Fluctuations & steady state within therapeutic range
4
Q
Measuring Concentrations
A
- Site of action most accurate, not possible
- Mostly measured in plasma
5
Q
Benefits of Plasma Measurement
A
- Non-invasive
- Correlation between plasma, therapeutic & toxic effects
6
Q
Free Drug Measuring
A
- Elicit pharmacological response
- Theoretically would be ideal from dosing, difficult
7
Q
Plasma Measuring
A
- Measuring plasma provides enough information
- Guide dosing
- Free + protein bound usually measured
8
Q
Oral Admin Time Curve
A
- Absorbed into blood
- Beginning, absorption rate > elimination rate
- Later, absorption = elimination (Cmax)
- After Cmax, elimination > absorption rate
9
Q
Plasma Concentration Curve
A
- High enough to have therapeutic effects
- Not high enough to induce toxicity
10
Q
Minimum Effective Concentration (MEC)
A
- Perform therapeutic effect
- Drugs below level have no effect
11
Q
Duration
A
- Length of time drug concentration above MEC
12
Q
Toxic Concentration
A
- Plasma concentrations exceed therapeutic range
13
Q
Therapeutic Range
A
- Above MEC, below toxic concentration
- Goal attain concentrations in range
14
Q
Therapeutic Range/Window Width
A
- Index of usage safety
15
Q
Narrow Range
A
- Difficult to administer
- Small effective window
- Therapeutic monitoring, ensure concentrations in target range
- Monitor through trough blood sample
16
Q
Onset of Action
A
- Lag time varies between different administration methods
- Rate & extent of absorption impact onset
- How soon drug effects occur
17
Q
Oral Onset of Action
A
- Lag time before MEC
18
Q
Continuous Intravenous Infusion
A
- Rate of entry stays constant
- No absorption, drug enters systemic circulation
- Plasma concentration rises
- Elimination rate = infusion rate
- Steady state (no change plasma levels)
19
Q
IV Bolus
A
- Rapid injection into blood
- Quick distribution
- eliminated over time
- Rate of elimination dependant on blood concentration
20
Q
Repeated Dosing
A
- Accumulation until plateau reached (steady state)
- High level, peak
- Low level, trough
21
Q
Steady State
A
- Peak & trough concentrations same between doses
22
Q
Reducing Fluctuations
A
- Continuous IV infusion
- Depot preparations
- Change dosing interval
23
Q
Continuous IV Infusion Characteristics
A
- Constant drug levels
- No peaks/troughs
- Not a feasible method
24
Q
Depot Preparations
A
- Release drug at slow, constant rate
- Minimizes peaks/troughs
25
Changing of Dose Intervals
- Same total daily dose
- Multiple times throughout day
- Reduce peaks/troughs
26
Clearance (Cl)
- Efficiency of irreversible elimination
- Volume of blood cleared per time unit
- Route of elimination
27
Total Clearance
- Sum of all elimination rates
- Determines dosage rate required to maintain concentration
28
Dosing Rate Equation
= plasma conc x clearance
29
Half Life (t1/2)
- Time to decrease plasma drug conc to 50%
- Determine time to reach steady state
- Time for decline in levels after administration
30
Half Life Equation
= (0.693xVd) / Cl
31
Time to Steady State
- 5 half lives (same drug repeatedly)
32
Constant Dose
- Time to reach steady state independent
- Size effects steady state concentration
33
Loading Dose
- Given if too long to reach steady state
- Large loading doses given to quickly acclimate patient
- Smaller maintenance doses follow to keep steady state
34
Loading Dose Equation
= target drug conc x Vd
- Assuming 100% bioavailability
35
Decline from Steady State
- Time for plasma conc to decline from steady state
- Independent of the dose
- 5 half lives = 97% eliminated
- 9 half lives = 100% eliminated
