Yeah, both pure diphenhydramine sourced from the usual places, and probably on a smaller scale the contents of Benadryl capsules, are definitely used in cutting heroin. I actually misspoke above, the capsules probably are the safest route. Inactive ingredients in the contents of the shell are listed as "anhydrous lactose, lactose monohydrate and magnesium stearate." Lactose is very common as a cutting agent in drugs so people are probably putting that in their veins anyway. Magnesium stearate is a little more problematic as it's not soluble in water, although it's not toxic. The little pink pills are going to contain all sorts of horrible shit OTOH.
e2a: Note I'm talking about the pills filled with powder. The capsules filled with gel contain God knows what that's going to clog up your veins something terrible and are probably even worse than the dry pills.
I know this is an old post, just happened to see it while looking up collapsing or clogging your veins.
I hope this info can help someone:
I spent a couple years IV'ing Benadryl (Benny's). I did it way too much, like couple capsules at a time several times a day.
Over the counter, equate brand, never tried the hard pink ones, always the clear/pink caps filled with powder.
I would just pinch off the end, dump it into a bottle cap and dump up to 3 or 4 of these at a time. Usually two. I would then do the ritual, draw and into the arm.
It should be noted that during this whole period, I was detoxing from opiates. Not acute detoxing, but more like the long drawn out slow burn detox.
Between the 'ritual' and the little woosy feeling I'd get from the Bennys, it would scratch that little itch for a while.
So, here's what eventually happened.
For a long time, there was no signs of any problems at all. This is actually kind of where I first ever had a vein collapse or become unusable. In short, the white residue leaves a little bit behind each time.
Now sure, everything leaves behind something, but this stuff is like concrete. Just take some and mix with water and let it dry, once it's sat overnight, it's hard as a brick and does not seem to become soluble again, just breaks into tinier 'chunks' when you water it.
So, increased blood pressure for sure, and still have that to this day, almost 10-11 years later without touching them. Which, I have zero desire to ever do that again.
If I did not have my prison sentence when it was, which forced me to stop anything until a few years in anyways, after I learned how everything works and then you can get whatever.
Side note: bennadryl is/was popular in prison, because you could easily enough complain to medical about allergies, and the second med after the initial was benadryl. (U had to complain the first med did not work). And then some convicts got the 50mg caps after that.
Users would consume the whole pill sheet, which held about 30 25mg Benny's, and be so dry mouthed and lightheaded off their ass, they would stay up all night and just not be in their right mind, lighting things on fire

etc, in a cellblock, def not thinking clear.
So, please, from someone who got lucky with years of abusing them. Swallow them, plug them, whatever you want to, just don't IV them.
You may be fine, for a long time, but eventually your arteries and veins will solidify and shutdown.
I still have hypertension, and when stressed or hot


it goes way up, like 190/120 the other day. Also have problems with my circulation, arms will go numb while sleeping and hands and feet frequently while awake and moving. I can never give plasma to earn money or just to do it anyways. I've tried, my blood never has a high enough "clear liquid content" and they always were like, you must be dehydrated just drink XYZ before you come back. Well it does not matter how much water or Gatorade or coconut water you drink or fasting, never goes back to normal. Try feeling eternally like you need to drink something because you feel dry all the time.
Heat exhaustion comes much easier. Probably a lot more stuff I can't even think of right now.
*Just don't, it will long term fuk you up.