Lecture 33: Clinical Pharmocokinetics 2

Question 1

RATIONAL DOSAGE REGIMEN

Answer 1

-Plan for drug administration over time

(Shouldn’t exceed minimum toxic [ ])

Based on

1) Theraputic window (Range of [ ] helping pt)
2) Clearance (Amount excreting body)
3) Vd (Volume of distribution)

Question 2

Theraputic Window

Answer 2

-Range of acceptable plasma levels

• Trough plasma [ ] = minimum effective [ ]
• Minimum toxic [ ] = peak plasma [ ]

Question 3

Maintenance Dose

Answer 3

-Used to obtain desired plasma [ ] over long periods of time and maintain steady state of drug in the body

Maintenance dose = dosing rate x dosing interval

(CLx TC/how many times a day)

Question 4

Loading Dose

Answer 4

-Used to obtain desired plasma [ ] rapidly

Loading dose = Vd X TC / F

Vd= Volume of distribution
TC = Target Plasma [ ]
F = Bioavailability (Always 1 with IV)

Question 5

Dosing rate

Answer 5

CL X TC / F

CL X C

CL= Clearance
TC = Target Plasma [ ]
F = Bioavailability (Always 1 with IV)

Question 6

How do fixed doses effect plasma level of drugs

Answer 6

fluctuations in the plasma level of the drug

Question 7

Single IV Injection

Graph

Answer 7

The plasma level will peak and decrease exponentially with time

Question 8

Multiple IV Injections

Graph

Answer 8

The plasma [ ] increases until a steady state is reached

-plasma [ ] fluctuates (Up and down and pointy at peak))

Question 9

Oral admission

Graphs

Types of release

Answer 9

Graph:

• Round peak
• upward climb (bc needs to be absorbed first)

Slow release = lower/delayed peak, higher levels @ later time, take it less, short half lives

Rapid release = higher/immediate peak, lower levels @ later time

Question 10

Describe steady state (Css)

Answer 10

• Amount given over time = amount eliminated over time
• Reached after 4 half-lives

Dosing rate-ss = rate of elimination-ss = CL X C/F

CL= Clearance
C= Concentration
F= Bioavailability

Question 11

Continuous IV Infusion

Answer 11

• Rate of drug entry: Constant
• Plasma [ ] increases until rate of input and output are equal (Steady state)

Css= Infusion rate/CL
(Steady state plasma [ ] = proportional to Infusion rate)

-Infusion stops = plasma [ ] declines to 0 (takes same amount of time to get to 0 that it took to reach steady state)

Question 12

Percentage of Steady state (Css) achieved after 1-4 half-lives

Answer 12

1 = 50%
2= 75%
3= 87.5%
4= 93.75% (all)

Question 13

Half-life equation

Answer 13

t 1/2 = 0.693 x Vd / CL

Question 14

PH Equation

Answer 14

PH - PK = log [unprotonated form]/[protonated form]

Question 15

Continuous IV

Answer 15

-plasma [ ] increases and levels off when reaches steady state (hump looking)