[johnisgood]

Desloratadine (Clarinex, Aerius) is a selective H1-antihistamine which functions as an inverse agonist at the histamine H1 receptor.

From Wikipedia:

> At very high doses, it is also an antagonist at various subtypes of the muscarinic acetylcholine receptors. This effect is not relevant for the drug's action at therapeutic doses.

Thus, it is an anticholinergic only at very high doses, and it does not readily pass the BBB, therefore drowsiness is NOT likely (probably at very high doses only). At any rate, it does not affect the CNS at therapeutic doses, so memory / cognition issues, along with drowsiness are not an issue.

FWIW "2% of Caucasians and 18% of people from African descent are desloratadine poor metabolizers.", meaning "In these people, the drug reaches threefold higher plasma concentrations at seven hours after intake, and it has a half-life of 89 hours (compared to a 27-hour half-life in normal metabolizers). Adverse effects were reported at similar rates in poor metabolizers, suggesting that it is not clinically relevant.".

[throwaway2037]

Is BBB == "blood-brain barrier"?

[johnisgood]

Yes.

[TechDebtDevin]

Do you know if there are any SNPs correlated with poor desloratadine metabolizers?

[johnisgood]

I do not think that there are any definitive single nucleotide polymorphisms (SNPs) currently known to be specifically correlated with poor desloratadine metabolism.

I think perhaps the genetic variation in the enzymes involves in its metabolism like UGT2B10 and CYP2C8 may contribute to differences in metabolism. There is just no conclusive identification of specific SNPs that definitively determine poor metabolizer status. The precise genetic variants (if any) have not yet been definitively pinpointed.

For all we know, the differences may be attributable to variations in study design, sample sizes, definition of what constitutes a "poor metabolizer", and genetic heterogeneity among populations. Some reported rates of poor metabolizers vary, some studies report around 7% overall and 20% in African descent individuals, while others suggest the figures I have mentioned. There was a somewhat recent randomized study in healthy Chinese subjects, and found no statistically significant association between the UGT2B10 or CYP2C8 genotypes.

What is clear is that while genetic factors are likely involved and poor metabolizer phenotype exists for the drug, no single genetic marker has yet been found to predict poor metabolism of this drug, and there is a notable interethnic difference in desloratadine metabolism.

TL;DR: Currently there is no definitive evidence linking specific SNPs to poor desloratadine metabolism, but genetic variation in enzymes like UGT2B10 and CYP2C8 is implicated, but further research is needed.

I hope this answers your question, but the bottom line is that more research is needed. If you know something, let me know though!

[TechDebtDevin]

Interesting, and thank you for the informative response. I have very weird reactions to cholinergic/anticholinergic drugs ranging from severe hallucinations to massive impacts to working memory. I've always figured there is something unique about that part of my biology but don't really no where to look to try and identify why.

[johnisgood]

I have weird or controversial reactions to most medications, especially psychiatric and drugs. I have no clue why. I have MS, I have brain lesions, they might play a part.

- For example nothing happened from 190 x 1 mg alprazolam + 0.5 L whiskey.

- None of the psychiatric medications worked for me (tried almost all there is, it took a long time). No pros, nor cons.

- Opiates do not cause euphoria, nor sedation for me. Without tolerance.

- The list goes on...

I have never figured out why medications affect me extremely differently from other people.

I took 5 x 50 mg DPH, nothing happened, then the next day I took it again, and I got anticholinergic toxicity. Perhaps it accumulated in this case, but yeah, it was one of the worst experiences I have had (delirium with dysphoric hallucinations, cognitive decline, memory issues). Took me months to recover. I have had auditory hallucinations for a couple of days, too.

What cholinergics and anticholinergics have you tried and what were your experiences?