What is the maximum single dose of acetaminophen per administration?

• A. 1500 mg
• B. 1000 mg
• C. 2000 mg
• D. 500 mg

Answer: (B)

The main idea here is safety of dosing to prevent liver injury from acetaminophen.

In adults, the maximum amount you should give in a single dose is 1000 mg. This limit helps minimize the amount of the toxic metabolite NAPQI that can form in the liver. When acetaminophen is taken in larger amounts at once, more drug is shunted into the CYP450 pathway, producing NAPQI faster than glutathione can neutralize it, which raises the risk of acute liver injury. Normally, acetaminophen is processed safely by sulfation and glucuronidation, but once those pathways are saturated, the toxic pathway dominates.

It’s also important to keep in mind that the total daily limit is generally about 4000 mg for healthy adults, with lower limits for those with liver disease, chronic alcohol use, or other risk factors. Some doses or products may present as lower per-dose amounts, but the per-administration maximum you should observe remains 1000 mg.

So, a single dose of up to 1000 mg is the safest upper limit per administration. Doses well above this (for example, 1500–2000 mg) are not appropriate per administration and increase hepatotoxic risk, while 500 mg is below the maximum per-dose threshold.