# Why 81mg of Aspirin for Heart Conditions? **URL:** \ **Category:** Factual Questions\ **Created:** [April 19, 2006, 4:22pm UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314 "2006-04-19T16:22:45Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![KarlGauss](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/karlgauss/32/3713_2.png) [@KarlGauss](https://boards.straightdope.com/u/KarlGauss)\ **Post date:** [April 20, 2006, 7:24am UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/21 "2006-04-20T07:24:55Z")
[QUOTE=scr4] Anyway, is it common for doctors to recommend a low-dose aspirin regimen to someone who doesn’t have any obvious signs of heart disease? Last time I went to the doctor he said: “You’re a male over 30 yrs old, so you should start taking 1 aspirin a day.” (I’d have a bit more confidence in his recommendation if he didn’t follow it up with: “Start out with the 325mg tablets and if you notice blood in your stool… er, umm, why don’t you start out with the 81mg tablets.”) [/QUOTE] The use of aspirin to prevent the first occurrence of cardiovascular disease (i.e. so-callled “primary prevention”) is a controversial area. Still, a consensus seems to have emerged that aspirin _should_ be given to prevent CV disease, but only in those people who are at least at moderately increased risk of CV disease compared to the rest of the population. Of course, this is where the controversy has now shifted - what is ‘at least moderately increased risk’ and how is it recognized? The American Heart Association guidelines for primary prevention recommend aspirin prophylaxis in all individuals with a 10-year risk of CV disease of 10 percent or more (this is their _ad hoc_ definition of “at least moderately increased risk”). How is such risk determined? By using the [Framingham risk score](http://www.cardiology.palo-alto.med.va.gov/tools/medcalc/fram/). ---
**Author:** ![irishgirl](https://avatars.discourse-cdn.com/v4/letter/i/8edcca/32.png) [@irishgirl](https://boards.straightdope.com/u/irishgirl)\ **Post date:** [April 20, 2006, 8:08am UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/22 "2006-04-20T08:08:22Z")
In the UK and Ireland ( and possibly the rest of europe, I don’t know) the standard “low-dose” aspirin for primary and secondary prevention is \*not \* 81mg- it’s 75mg. Just so you know. ---
**Author:** ![Jeff\_Lichtman](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jeff_lichtman/32/1531_2.png) [@Jeff\_Lichtman](https://boards.straightdope.com/u/Jeff_Lichtman)\ **Post date:** [April 21, 2006, 6:32am UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/23 "2006-04-21T06:32:00Z")
81 mg is almost exactly 1.25 grains - a grain is 1/7000 pound. I suspect aspirin doses in the U.S. were originally measured in grains, and that the standard doses were kept about the same size when manufacturers converted to metric units. ---
**Author:** ![outlierrn](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/outlierrn/32/3005_2.png) [@outlierrn](https://boards.straightdope.com/u/outlierrn)\ **Post date:** [April 21, 2006, 7:00am UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/24 "2006-04-21T07:00:24Z")
[QUOTE=Jeff Lichtman] 81 mg is almost exactly 1.25 grains - a grain is 1/7000 pound. I suspect aspirin doses in the U.S. were originally measured in grains, and that the standard doses were kept about the same size when manufacturers converted to metric units. [/QUOTE] correct, in fact you’ll still see some of the old docs write 5-10 grains aspirin ---
**Author:** ![Sal\_Ammoniac](https://avatars.discourse-cdn.com/v4/letter/s/8dc957/32.png) [@Sal\_Ammoniac](https://boards.straightdope.com/u/Sal_Ammoniac)\ **Post date:** [April 21, 2006, 2:21pm UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/25 "2006-04-21T14:21:44Z")
[QUOTE=Jeff Lichtman] 81 mg is almost exactly 1.25 grains - a grain is 1/7000 pound. I suspect aspirin doses in the U.S. were originally measured in grains, and that the standard doses were kept about the same size when manufacturers converted to metric units. [/QUOTE] Bet you’re right. I was looking at old aspirin tins on eBay, and the dosages are always expressed in grains. ---
**Author:** ![groman](https://avatars.discourse-cdn.com/v4/letter/g/73ab20/32.png) [@groman](https://boards.straightdope.com/u/groman)\ **Post date:** [April 21, 2006, 2:24pm UTC](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314/26 "2006-04-21T14:24:56Z")
[QUOTE=Jeff Lichtman] 81 mg is almost exactly 1.25 grains - a grain is 1/7000 pound. I suspect aspirin doses in the U.S. were originally measured in grains, and that the standard doses were kept about the same size when manufacturers converted to metric units. [/QUOTE] 1.25 Grain is also the standard dosage for baby aspirin, so it makes sense. [Previous page](https://boards.straightdope.com/t/why-81mg-of-aspirin-for-heart-conditions/353314.md?page=1)