N&PD Moderators: Skorpio
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This is a fascinating concept, thank you for starting this groundbreaking thread!adder
Bluelighter
I've used Dramamine (dimenhydrinate) occasionally to overcome nausea associated with opiates, and I've used diphenhydramine quite extensively as a sleeping aid. Dimenhydrinate is the chlorotheophylline salt of diphenhydramine, and it is diphenhydramine which is responsible for its antihistaminergic and anticholinergic effects. I've never noticed any dryness or reduced vaginal lubrication as side effects of these drugs. However, I have noticed that I sometimes have dry eyes in the morning after taking diphenhydramine, especially if I've exceeded 50 mg. I presume it's due to antagonism of muscarinic acetylcholine receptors.
At very high doses, I'm sure dimenhydrinate can cause vaginal dryness, along with a whole range of other anticholinergic and antihistaminergic side effects. The antihistamines are not recreational in my opinion, and trying to trip or somehow get high on massive overdoses of these drugs is stupid and dangerous.
I have experienced the effect that the OP is referring to when taking alimemazine or promethazine in therapeutic doses. These are phenothiazine-class antihistamines which are used as sleeping aids in some European countries. I believe that they have more pronounced anticholinergic activity. They're quite horrible drugs really, and I'll never touch them again.adder
Bluelighter
Drugs like dimenhydrinate or diphenhydramine also have anticholergic effects acting on mAch receptors. I don't think it's a very good idea to take dimenhydrinate/diphenhydramine for nausea associated with opioid use. As they produce effects similar to tropane alkaloids when used recreationally, they boost opioids effects. I used to smoke 200-250mg of Atropa belladonna leaves with after shooting morphine, that got me nodding like nothing else (mixing morphine with scopolamine on purpose to induce twilight sleep and make a person forget about pain must give similar effects).
Well Sir, I beg to differ. When used in therapeutic doses, 25-50 mg, they're actually quite brilliant for this purpose. In this dosage range, anticholinergic side effects are not usually noticeable. There may be a slight potentiation effect on opioid sedation, but not so much as to make it dangerous in my opinion.
Using potent anticholinergics or very high doses of antihistamines to boost the effects with opioids is an entirely different matter.