I took two tablets about an hour ago and now would like to drink an energy drink to give me a boost.
I've been told this is potentially unsafe. Is there any dangers to this?
Medical Sciences Stack Exchange is a question and answer site for professionals in medical and allied health fields, students of those professions, related academics, and others with a sound understanding of medicine and healthcare-related sciences. It only takes a minute to sign up.Sign up to join this community
The question appears to be motivated by headlines similar to this
Mixing large doses of both acetaminophen painkiller and caffeine may increase risk of liver damage
where it states
WASHINGTON, Sept. 26 2007 — Consuming large amounts of caffeine while taking acetaminophen, one of the most widely used painkillers in the United States, could potentially cause liver damage, according to a preliminary laboratory study reported in the Oct. 15 print issue of ACS’ Chemical Research in Toxicology, a monthly journal. The toxic interaction could occur not only from drinking caffeinated beverages while taking the painkiller but also from using large amounts of medications that intentionally combine caffeine and acetaminophen for the treatment of migraine headaches, menstrual discomfort and other conditions, the researchers say.
This was a very preliminary study using genetically modified bacteria
Chemist Sid Nelson, Ph.D., and colleagues, of the University of Washington in Seattle, tested the effects of acetaminophen and caffeine on E. coli bacteria genetically engineered to express a key human enzyme in the liver that detoxifies many prescription and nonprescription drugs. The researchers found that caffeine triples the amount of a toxic byproduct, N-acetyl-p-benzoquinone imine (NAPQI), that the enzyme produces while breaking down acetaminophen. This same toxin is responsible for liver damage and failure in toxic alcohol-acetaminophen interactions, they say.
In previous studies, the same researchers showed that high doses of caffeine can increase the severity of liver damage in rats with acetaminophen-induced liver damage, thus supporting the current finding.
But crucially the bacteria were exposed to megadoses of both acetaminophen and caffeine.
Now, caffeine is regularly provided in combination with acetaminophen in some analgesic compounds despite this ancient warning.
The latest data from 2017 I can find suggests that the interaction in humans is somewhat less dramatic, and caffeine may even help reduce acetaminophen toxicity!
In conclusion, the impact of CAF on APAP‐induced hepatotoxicity was here investigated in humans by simultaneously considering drug effects of CAF on APAP at both the PK and the PD level. It was shown that CAF has a significant effect on APAP‐induced hepatotoxicity due to a co‐administration of both drugs. Key results demonstrate, on the one hand, that CAF might favor a reduction of APAP‐induced hepatotoxicity in humans at the PK and the PD levels by reducing the concentrations of NAPQI, which is supposed to be the reactive metabolite of APAP,2 as well as by positively regulating genes playing an essential role in the development of toxicity, respectively. On the other hand, CAF might also potentiate APAP‐induced toxicity by affecting crucial genes, such as FOS, that may support the activation of cell death pathways. Although key outcomes of the study demonstrated inhibitory and stimulatory effects of CAF on APAP, the question if CAF potentiates or diminishes the hepatotoxicity caused by extensive exposure of APAP partly remains open.
So, to answer the question, the risk of harm from an energy drink after ingestion of 1G of acetaminophen is close to nil.
As for the maximum dose of acetaminophen, in adults this is 1G q4 - q6 hourly to a maximum of 4G and not 2G as mentioned in the other answer. The makers of Tylenol have suggested that this be reduced to 3G since people often combine analgesics without realizing that the other product might also contain acetaminophen, but this doesn't change the fact that the safe dose from all sources remains 4G daily.