Laboratory Values and Half life

Laboratory values

reflecting function of liver and kidneys need to be looked at

BUN

Creatinine

Laboratory Values

• Kidney Function

ALT
AST or SGOD

ALP

Bilirubin Levels

Laboratory Values

• Liver Function

Alanine Aminotransferase ALT

Laboratory Values

• Liver function

  • elevated in hepatitis

Aspartate Aminotransferase

Laboratory Values

• Liver function

  • elevated in liver disease

ALP

Laboratory Values

• Liver function

  • elevated in biliary tract disease

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.

Toxic Levels

Excessive level of a drug in the body

• Single large dose

• Repeated small doses

• Slow metabolism which allows drug to accumulate in the body

• Slow excretion from the body by the kidneys or gastrointestinal tract

onset, peak and duration

Serum drug levels indicate the _______________ of the drug action

Half life

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

Half life

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

Half life

A measure of the rate at which drugs are removed from the body

five half-lives

Most drugs are considered to be effectively removed after about

Short ½ life

• need to take frequently

• compliance may be a problem

  • example: acyclovir 5 times daily

long ½ 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

4-5 half-lives

Steady state

• Typically occurs after ______ of administration

Loading dose

to reach a steady state more quickly, a __________ may be ordered 

• This is a higher initial dose