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  • BDD Moderators: Keif’ Richards

Are all antipsychotics antihistamines?

A

Anon54

Ex-Bluelighter
Joined
Jun 11, 2010
Messages
861
On wiki it states that Seroquel is a strong antihistamine.

Does this apply for all antipychotics?

how does seroquels antihistamine effect vary from the other common antiphychotics?

I suffer from allergies & am consitering taking a low dose Zyprexa for insomnia regualy & it would be a bonus if it could help with allergies as well.

I know antipychotics block H1 receptors.

is blocking H1 receptors resposible for the effect of antihistamines?

meaning the stronger the H1 block , the stronger the antihistamine effect?

if this is the case does someone have a link to a comparison of how much each antipychotic blocks H1 receptors?
 
I don't know any antipsychotic that wouldn't be an antihistamine. Typical antipsychotics like chlorpromazine and perphenazine are antihistamines, and surprisingly atypical ones like seroquel and risperidone are too. Probably the same structural features that make a molecule bind to dopamine receptors, also make it bind to H1 receptors.

I've had a psychotic disorder and I first used perphenazine and then changed to risperidone. Both make me sleep better because of the antihistaminic effect.
 
I don't think the new atypical antipsychotics Olanzapine (Zyprexa) and Aripiprazole (Abilify) have any antihistamine properties. I could be wrong, though.
 
^^ http://www.ncbi.nlm.nih.gov/pubmed/10227113

In isolated tissue studies, olanzapine potently blocked agonist-induced effects at alpha 1-adrenergic and histamine H1 receptors (KB = 9 and 19 nM, respectively). Thus, olanzapine was an antagonist at all receptors investigated and was a particularly potent antagonist at 5-HT2A, 5-HT2B, 5-HT2C, alpha 1-adrenergic and histamine H1 receptors.
Click to expand...
 
so we've establised that drugs that block H1 receptors are antiphychotics, right?

seroquel in low doses actually doesnt block dopamine ive read somewhere. not untill about 200mg & the reason why it's still sedating is the same reason drugs like diphenhydramine are.

ive got a script for zyprexa. it would be good to know that i dont have to buy claratin or something whenever i get allergies real bad

btw i know mirtazepine isnt an antipsychotic but on wiki it says its a good antihistamine for those who suffer from allergies. thats what explains its sedative qualities
 
sorry to bump this..;

but is the defention of an anithistamine a drug that blocks H1 receptors?
 
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC487011/figure/i1523-5998-6-s2-3-f01/
here is a link comparing the effects on H1 receptors from different anti-psychotics taken from:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC487011/

it gives a comparison reading of zyprexa blocking H1 with a score of 1149
it only gives seroquel a score of of 5.2 (thats a massive difference)

this website may have incorrect info. it doesn' t sound right!!. so i suppose zyprexa is by far the superior antihistamine??

so if i wanna take a anti-psychotic thats gunna help my allergies i should take zyprexa instead or seroquel?

does anyone elese no of any links to sites comparing anti-psychotic action on h1 receptors. the site above was the 1st one i found when i googled "comparison antipsychotic affinity" yet it seems a bit unbeilable
 
Last edited:
sorry to have to bump this again.
so from the above post. would that mean zyprexa is by far the strongest antihistamine?
 
I know this is an old thread. But I was wondering again today about how well different antihistamines are good for the treatment of allergies or itchyness (which some may experience from opiates)
Seroquel is the only Antipsychotic listed as an antihistamine on wikipedia. yet according to the following chart Seroquel scores 5.2 & Zyprexa scores 1149 which is a significant different.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC487011/figure/i1523-5998-6-s2-3-f01/
I dont have to much knowledge on advanced pharmacology but would Zyprexas higher affinity to the H1 receptor mean that it's a much stronger antihistamine?
 
Not always:

Binding affinity data alone does not determine the overall potency of a drug. Potency is a result of the complex interplay of both the binding affinity and the ligand efficacy. Ligand efficacy refers to the ability of the ligand to produce a biological response upon binding to the target receptor and the quantitative magnitude of this response. This response may be as an agonist, antagonist, or inverse agonist, depending on the physiological response produced.
Click to expand...

[Source]

Interesting topic, however. I've never taken Zyprexa but I know Seroquel is an extremely sedating antihistamine even at low doses (25mg or less, I've even gone to sleep on 12.5mg!)
 
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