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Thread: which 1st Generation Antihistamines have least/no anticholinergic effects?

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    which 1st Generation Antihistamines have least/no anticholinergic effects? 
    #1
    which 1st Antihistamines have least/no anticholinergic effects?

    Im in the U.K Diphenhydramine, Promethazine are both OTC Antihistamines i usually use when using Opiates like Oxy, DHC, Codeine, Poppy Pod Tea etc

    But ive read a warning that using anticholinergic antihistamines alongside Morphine can pose some problems.

    How serious should this warning be taken? Because i dont want to be itching like futhermucker!

    Thanks.
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    #2
    All the 1st generation anti-histamines have anti-cholinergic side effects. But why does it need to be first generation? Loratadine, fexofenadine or cetirizine would reduce itch and have no anti-cholinergic activity.
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    #3
    Bluelight Crew nAON's Avatar
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    ^ this, the reason they reason they are all classed as first gen is because of their shared anticholinergic effects.

    2nd and 3rd gen are quite widely available OTC though, I think cetirizine ad loratadine are the most common in pharmacies.
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    #4
    I believe he wants the potentiation that 2nd and 3rd gens won't provide. Unfortunately OP - if this is the case - you can't have one without the other. The reason they potentiate opioids is due to the sedation and other effects of their anticholinergic/antimuscarinic properties.

    I haven't heard of a problem combining morphine and anticholinergics before and did so for years so I'd love to see sources about any problems combining them. I say this not to challenge you or use my use as evidence you're wrong but rather out of concern that I was unknowingly being reckless and would like to know more. Thanks!
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    #5
    Thanks for the replies people.

    I decided not to get the Morphine after all, as it just prolongs the agony (worsens my Anxiety and Depression) after ive used Opiates, needless to say on another day il be weaker and give in to the pull of it!

    I wasnt actually looking for any potentiation as this was (would of been) my first time using Morphine and just wanted to stop the itchiness, so i have a 2nd generation Antihistamines (Cetirizine) in my house that i could use for this.

    Sorry Cane i cant find the literature i was looking for, the only thing i could find was to do with using Anticholinergics in Geriatrics.
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    #6
    Bluelight Crew effie's Avatar
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    Hydroxyzine has significantly less anticholinergic action than the other 1st gen antihistamines (but I know you're not a fan Pete!)

    As others said, of the 1st gen do have at least some degree of anticholinergic action. 2nd gen antihistamines don't cross the blood-brain barrier, aren't sedating and aren't anticholinergics.. so you either get bonus potentiation but with possible anticholinergic side effects, or no potentiation but also no anticholinergic effects. Many 1st gen antihistamines also inhibit CYP-450 enzymes where as most 2nd gen don't.

    The only interaction I know of between morphine and 1st generation antihistamines is increased sedation. I suppose urinary retention could also be a problem, as both opioids and anticholinergics can cause that. Both my regular interaction checkers (here and here) don't throw up anything else.

    Glad you managed to stay away (for today at least) and cetirizine is fine for opioid itch in my experience
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    #7
    Bluelighter ErgicMergic's Avatar
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    I don't understand why Hydroxyzine is so widely prescribed as a sleep aid if it has relatively little anti-cholinergenic action. Are the 5-HT2A lowering (inverse agonist) effects the primary mechanism of sedation?

    Personally, I've always preferred low dose Doxylamine (6.25-12.5mg) to Hydroxyzine as a sleep aid, due to a shorter half life, meaning less of a morning hangover.

    Effie, cetirizine is my favorite anti-histamine for itchies, it doesn't dirty up the high with the nasty anti-cholinergenic effects that 1st gen anti-histamines provide.
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    #8
    I'm with you EM - I don't really understand how hydroxyzine works (although admittedly I haven't really tried ). Anyone out there able to educate us?

    I also love doxylamine if I need a sleep aid and prefer cetirizine as my all-purpose antihistamine but admittedly do like some first gens with my opioids.
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    #9
    I may be weaker today and actually get the Morphine and luckily enough i have a full packet of Certirizine!

    I do have one (actually a few) question(s) though with regards to Morphine?

    Is it a very sociable drug? (Obviously i guess this may be dose dependant) Is it obvious to others that you are intoxicated? (I guess this may again be dose dependant)

    The reason i ask is that im going to out to a club night/gig tonight 'Alkaline Trio' are playing in my city tonight, so i was of possibly playing with the idea of throwing a little Morphine into the mix.

    Good/bad idea?

    If no replies then 'mai pen rai' (no worries) Il ask these questions in my other 'Morphine' thead.

    Thanks all.
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    #10
    Mixing alcohol, opiates (and prob benzos..) is the worst idea. Pretty much in practice AND execution.

    That said (and please do be very cautious).. Many a night in the local bar districts prowled while high on oxy, sippin whatever was put in my hand went wonderfully. Walk, take a cab, something. Don't drive on opiates and even 1-2 drinks; it's such a huge impairment of judgement. I do self checks while on substances, and this is the worst for being non-psychs (in myself anyway). I imagine it would only get worse to add.. the number of cars friends and I have crashed / banged up on the behalf of someone drinking, on both sides of the wheel.. Not everyone has all their screws in w/ loc tite. (thank the first person like that for this forum! )

    Sorry for the ramble. Don't over-do the booze. No more than 2 drinks and hour or the alcohol will override the opiate feeling.. and then you've wasted some precious gold (to someone, somewhere.. certainly not me ) That and you'll prob toss it all back up.. 99.5% I puke after drinking while high on, well any, opiate (to excess anyway - learn your limits and coast among the clouds of bliss. And meanwhile the rest of the bar is full of, well, nothing interesting. Maybe on the second round an interesting face pops up. Alcohol alone isn't my wingman, but add some oxy and I'd be playing "game" (Ick) I wasn't aware I had.

    have fun, and be safe!
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    #11
    Quote Originally Posted by Pjkt2501 View Post
    Mixing alcohol, opiates (and prob benzos..) is the worst idea. Pretty much in practice AND execution.

    That said (and please do be very cautious).. Many a night in the local bar districts prowled while high on oxy, sippin whatever was put in my hand went wonderfully. Walk, take a cab, something. Don't drive on opiates and even 1-2 drinks; it's such a huge impairment of judgement. I do self checks while on substances, and this is the worst for being non-psychs (in myself anyway). I imagine it would only get worse to add.. the number of cars friends and I have crashed / banged up on the behalf of someone drinking, on both sides of the wheel.. Not everyone has all their screws in w/ loc tite. (thank the first person like that for this forum! )

    Sorry for the ramble. Don't over-do the booze. No more than 2 drinks and hour or the alcohol will override the opiate feeling.. and then you've wasted some precious gold (to someone, somewhere.. certainly not me ) That and you'll prob toss it all back up.. 99.5% I puke after drinking while high on, well any, opiate (to excess anyway - learn your limits and coast among the clouds of bliss. And meanwhile the rest of the bar is full of, well, nothing interesting. Maybe on the second round an interesting face pops up. Alcohol alone isn't my wingman, but add some oxy and I'd be playing "game" (Ick) I wasn't aware I had.

    have fun, and be safe!
    Haha. Thanks, and great post btw.

    I will be arriving and (hopefully) leaving the venue on foot as it's only about a 2 mile walk, weather depending we may get a taxi or we may not so at least that pretty much rules out the car crash scenario.

    Also im not a big drinker anyway, a couple of beers even when im sober is where i usually keep it, unless im Benzo'd up out my face and just blackout and drink every drink in the room and always regret everything il never remember (apart from friends 2nd hand accounts of my embarrasing/funny/strange behaviour!)

    I generally have a NO ALCOHOL rule that i stick to very ridgedly whilst using Opiates, because 99.9% of the time on using Opiate im also using Benzos, and Benzos + Opiates = Dangerous or fun depending on tolerance (Im fortunate/unfortunate) to have a ridiculous tolerance to both but anyway tonight i wont be taking any Benzos, infact the last time i would have used Benzos will have been about 48 Hours previous to tonights activities and even though im aware im a Benzo fiend who generally uses Diazepam i do realise its massive half life and the amounts ive used over the past couple of years has obviously caused a build up in my system because any time i am to drink largish amounts of alcohol even without having taken any benzos for a number of days/weeks i still suffer very bad amnesia!

    Which is something alcohol, even in largish doses never used to give me.

    And besides i always think Opiates + Benzos + Alcohol = High risk of death. (not to say i havent done many things that have been fatally risky in the past)
    Also im lucky enough that the friend who's going to the gig with me has a high knownledge of Opiate abuse as all 4 of his brothers and sisters are/were Heroin addicts.

    Thanks everyone.
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    #12
    Bluelight Crew effie's Avatar
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    Quote Originally Posted by Cane2theLeft View Post
    I'm with you EM - I don't really understand how hydroxyzine works (although admittedly I haven't really tried ). Anyone out there able to educate us?

    I also love doxylamine if I need a sleep aid and prefer cetirizine as my all-purpose antihistamine but admittedly do like some first gens with my opioids.
    Hydroxyzine has a low affinity for muscarinic acetylcholine receptors, unlike other 1st gens, so it has low anticholinergic action. It's sedatative effects come from antagonism of H1 receptors, I believe? So unrelated to any antcholinergic action as far as I know - it's just that other 1st gen antihistamines have prominent antihistamine and anticholinergic action. Not sure which is more important for their sedatory effects, and it is odd that hydroxyzine is used for sleep when by rights it should be less sedating than the other 1st gens, unless there is something else going on.. First to admit my neuropharmacology needs a little work though so this may not be right. Hydroxyzine is pretty unusual all round with it's 5-HT2A antagonist / anxiolytic action as well as it's H1 antagonism. Maybe the antiserotonergic action does add to the sedation.

    Cetirizine is a good 2nd gen antihistamine definitely, but promethazine will always have a place in my heart for opioids. 75mg max though or I start to feel pretty icky.

    Glad you're going to take it steady tonight Pete
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    #13
    If it was solely due to h1 receptor antagonism (or rather inverse agonism), why wouldn't ALL antihistamine (2nd gen onward) be sedating?

    After perusing the wikipedia page on the subject, it seems its a more focused selectivity for specific H1 receptors that reduces side effects such as sedation in later generations of antihistamines.
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    #14
    Bluelight Crew effie's Avatar
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    ^ but 2nd gen antihistamines don't cross the blood-brain barrier, where as 1st gen ones do.

    I'm currently reading wikipedia too haha, the pharmacology bits are pretty decent for this particular topic
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    #15
    Ah, that makes sense, thanks, f.
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    #16
    Bluelight Crew effie's Avatar
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    Nps Not sure it's fully explained by what we have here but my current psychopharm texts don't look at antihistamines much. Hydroxyzine certainly is a slightly unusual one.
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    #17
    Hi all im back from my night out and it was a bit of a letdown tbh

    Had a couple of beers and usual xxxmg dose of Diazepam before going out, i wasnt benzo'd up at all or drunk and still suffered some General and Social Anxiety.

    Home now with stinging eyes, a lot less money in my pocket and not a lot of fun to show for it!

    Makes me almost regretful that i didnt give into my urges of the past 2 days and had actually of gone and got that ORAL Morphine Sulphate solution.

    Im sure i would of had a better night.....
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