LABORATORY VALUES + HALF LIFE

liver and kidneys

Laboratory values reflecting function of_________ need to be looked at

BUN and Creatinine

what to assess for kidney function?

ALT alanine aminotransferase
AST or SGOT Aspartate aminotransferase

ALP -

Bilirubin levels

Liver function test (LFT)

ALT alanine aminotransferase

elevated in hepatitis)

AST/ SGOT asparate aminotransferase

elevated in liver disease

ALP

elevated in biliary tract disease

Bilirubin level

for infant

Gallstones in adult

Serum Drug levels

• Laboratory measurement of the amount of drug in the blood at a particular time

• A minimum effective concentration (MEC) must be present before a drug exerts its action on a cell.

minimum effective concentration (MEC)

• A _____________ must be present before a drug exerts its action on a cell.

Toxic levels

Excessive level of a drug in the body

• single large dose

• multiple small doses

• slow metabolism

• slow excretion

what causes toxic levels?

• Serum drug levels

• ________indicate the onset, peak and duration of the drug action

No

Do we do serum drug levels for all drugs?

1. narrow margin of safety

2. check if drug is at therapeutic levels

3. overdose suspected

When do we need serum drug levels?

Half-life

-determine how often a drug needs to be given to remain in a therapeutic range

The time it takes for one half of the original amount of a drug in the body to be removed

5

Most drugs are considered to be effectively removed after about ____half-lives

how often

Half-life determines ______ a drug is given

1. Daily in the morning

2. At bedtime

3. Q.I.D - four times a day

4. T.I.D - three times a day

5. Q4 hours - every four hours

6. Q 12 hours - 9 am and 9 pm

time of administration (N.O.T)

Short half life

• need to take frequently

• compliance may be a problem

  • example: acyclovir 5 times daily

Long half life

• pt has an adverse reaction

• the drug will be in the body for hours or days

  • example: Cialis T1/2 = 17 hours

Steady State

• Where the amount of drug excreted is equal to the amount of drug absorbed with each dose

• Giving more drug could cause toxicity

• Giving less drug would not be therapeutic

• Typically occurs after 4-5 half-lives of administration

Drugs with a very long half-life make take a longer time to reach a steady state

4-5

Steady State occurs after _____ half lives of administration

loading dose

With certain drugs, to reach a steady state more quickly, a_________may be ordered 

• This is a higher initial dose