Acetaminophen

Question 1

What is the chemical name for acetaminophen?

Answer 1

N-Acetyl-P-Aminophenol (APAP)

Question 2

How is acetaminophen classified?

Answer 2

A “miscellaneous” analgesic - blocks COX-3

Question 3

What is acetaminophen’s (Tylenol) mechanism of action?

Answer 3

• Inhibits COX3 - acts more upon CNS COX than peripheral COX (centrally)
• Does not:
  
  • inhibit platelet aggregation
  • irritate GI tract
  • cause bronchoconstriction

Question 4

Where is acetaminophen metabolized? And what about the metabolite? Half-life?

Answer 4

• Metabolized by liver
• Metabolite - hepatotoxic and nephrotoxic
• Half-life - 1-4 hours

Question 5

What are the uses for acetaminophen?

Answer 5

• Analgesic
• Antipyretic
• Equally potent to aspirin

Question 6

What is the #1 cause for liver failure in the US?

Answer 6

acetaminophen

Question 7

What is the maximum dose of acetaminophen? And can it be used for anti-inflammatory?

Answer 7

• Max dose: 4000 mg per day
• Not anti-inflammatory

Question 8

acetaminophen and aspirin are equally ___________ and equally __________. So why is acetaminophen less useful clinically?

Answer 8

• efficacious (reduces same degree of pain)
• potent (same dose in mg needed for effect)
• Because it is not anti-inflammatory

Question 9

What’s the dosing with acetaminophen (Tylenol)?

Answer 9

• Children: 10-15 mg/kg per dose every 4-6 hours as needed, don’t exceed 2.6 g in 24 hours (5 doses)
• Adults: 325-650 mg every 4-6 hours or 1000 mg 3-4 times/day, not to exceed 4 g per day

Question 10

What is the max dose of acetaminophen in patients who regularly consume alcohol?

Answer 10

Not to exceed 2 grams per day

Question 11

Avoid giving acetaminophen in patients with?

Answer 11

• Liver disease/dysfunction
• Alcoholism

Question 12

What is a very important drug interaction of acetaminophen?

Answer 12

Warfarin (Coumadin)

It causes enhanced anticoagulation - increased bleeding risk