Download Applied PK Critical Care

PHARMCOKINETICS
ALLIE PUNKE
CRITICAL CARE
ABSORPTION
ABSORPTION
• Passive diffusion OR Carrier-mediated absorption is
affected in critically ill patients?
• What is the preferred route to feed a critically ill
patient? Why?
• What class of drugs may further decrease gut blood
flow (and therefore absorption)?
• If given medication for stress ulcer prophylaxis, how
can this affect absorption?
ABSORPTION
• AB was admitted to the ICU. She is being started on
enteral nutrition. What (if any) modifications should
be made avoid an interaction with phenytoin?
• A. Nothing. It does not interact with phenytoin.
• B. Stop the feedings for about 30 minutes when giving
phenytoin to prevent a high concentration
• C. Stop the feedings for about 2 hours when giving
phenytoin
• D. The phenytoin dose should be increased to counteract
any absorption problems.
ABSORPTION
• When a patient is receiving enteral nutrition, there
are a few medications that interact with the
feedings.
• Phenytoin
• Effect: Dec. serum levels
• What to do: Hold tube feedings ~2 hours around dose
• Warfarin
• Effect: Decreased INR
• What to do: Hold tube feedings or increase dose (more so if
expecting to be on feedings for long term)
• +/- Fluroquinolones
• Effect: Maybe decreased levels…maybe not clinically
significant. Also, can depend on site of infection (UTI vs
bacteremia)
CRITICAL CARE
VOLUME OF DISTRIBUTION
VOLUME OF DISTRIBUTION
• What are some factors that can change Vd in ICU
patients?
• Giving large volume of fluids
• pH changes
• Protein binding
• Albumin is…. Increased Or decreased in patients?
• AAG is….Increased Or decreased in patients?
VOLUME OF DISTRIBUTION
• MB is admitted to the ICU. Her pH is 7.18. Which of
the following types of drugs would have an
increased volume of distribution?
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•
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•
A. Acidic drugs
B. Basic drugs
C. Neither
D. Both
VOLUME OF DISTRIBUTION
• AB is admitted to the ICU and needs to be started
on an aminoglycoside. Based on other critically ill
patients, AB will also likely require:
• A. Higher loading dose
• B. Lower loading dose
• C. Loading dose will not change
Follow up: Why did we give AB a higher LD?
• A. Increased excretion of the drug
• B. Increased volume of distribution
• C. Both
• D. Neither
VOLUME OF DISTRIBUTION
• Remember…
• Volume of distribution is used to calculate LD
• Clearance is used to calculate MD
• Be able to take these principles and apply to a patient’s
dosing regimen
CRITICAL CARE
METABOLISM
METABOLISM
• Be able to recognize which drugs are low E vs high E
(as well as the equations).
• Be able to recognize which drugs are bound to
albumin vs AAG
METABOLISM
• AB is a patient in the ICU. Her albumin level recently
fell to 1.9 from 4. Do any of her drugs need to be
adjusted?
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•
•
•
A. Phenytoin dose needs to be lowered.
B. Phenytoin and morphine doses need to be lowered.
C. Ceftriaxone dose needs to be lowered.
D. Morphine dose needs to be lowered.
METABOLISM
METABOLISM
• AB is started on propofol for sedation. Her albumin
level is still low around 2.4. Should the propofol dose
be adjusted?
•
•
•
•
A. Yes, the Css and Css,u are both affected.
B. No, neither the Css or Css,u are affected.
C. Yes, because the Css is affected.
D. Yes, because the Css,u is affected.
CRITICAL CARE
EXCRETION
EXCRETION
• Renal function….
• Decreased GFR
• Difficult to determine
• Acute kidney injury possibly may receive CRRT
• Fluctuating status of renal excretion
QUESTIONS?
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