Antihistamines

[Grey_Area]

I seem to be able to find articles that say antihistamines are both good and bad...I've noticed when taking cetirizine for my hayfever that I get less "restless legs". Any further info?

[JayPwP]

You will find the same issue with many therapies / molecules 😆😆😆

[Rufous2]

That's interesting, hadn't heard of antihistamines lessening RLS. I did run across a study that used AI to screen existing drugs for those that might be useful in PD, and Levocetirizine was one of two antihistamines that showed promise.

ncbi.nlm.nih.gov/pmc/articl...

"The study objective was to use artificial intelligence to rank the most promising repurposed drug candidates for PD."

"The top predicted adjuvant PD therapies included ebastine, an antihistamine for perennial allergic rhinitis; levocetirizine, another antihistamine; vancomycin, a powerful antibiotic; captopril, an angiotensin-converting enzyme (ACE) inhibitor; and neramexane, an N-methyl-D-aspartate (NMDA) receptor agonist. Cross-domain text mining predicted that antihistamines exhibit the capacity to synergistically alleviate Parkinsonian symptoms when used with dopamine modulators like levodopa or levodopa–carbidopa. The relationship patterns among the identified adjuvant candidates suggest that the likely therapeutic mechanism(s) of action of antihistamines for combatting the multi-factorial PD pathology include counteracting oxidative stress, amending the balance of neurotransmitters, and decreasing the proliferation of inflammatory mediators."

[Grey_Area in reply to Rufous2]

Yep, I found that too, but also a number of articles suggesting antihistamines reduced the effectiveness of L-Dopa.

Also this from the ever present mayo clinic;

"Some of the antihistamines are also used to prevent motion sickness, nausea, vomiting, and dizziness. In patients with Parkinson's disease, diphenhydramine may be used to decrease stiffness and tremors. Also, the syrup form of diphenhydramine is used to relieve the cough due to colds or hay fever."

[Rufous2]

It seems sedating antihistamines like Benadryl (diphenhydramine) have a beneficial effect on motor function via their anticholinergic properties. That same attribute can contribute to dementia though, so not a great trade-off, IMO.

I'm intrigued by the notion that some of the newer antihistamines act as antioxidants and anti-inflammatories, as demonstrated in this mouse study;

Parkinsonism Attenuation by Antihistamines via Downregulating the Oxidative Stress, Histamine, and Inflammation pubs.acs.org/doi/10.1021/ac...

Ebastine isn't available in the US, but sounds like it would be worth trying if it was. And this might be a real stretch, but I wonder if palmitoylethanolamide's effectiveness in PD stems from its ability to stabilize mast cells. Have you ever tried it or quercetin (another mast cell stabilizer) for your allergies? Would be interesting to know if either of these molecules reduces RLS.

[Ctime]

I would agree that allergy medicines help my symptoms. I am not sure though if it is because not being miserable with allergic rhinitis makes it easier to deal with Parkinson's or if the medicines actually help with the Parkinson's symptoms. I take my long acting antihistamine at night so it does not interfere with LDopa (none at night on my regimen).

As per the articles that others cite, there is a little evidence that the antihistamines that have an anti inflammatory mechanism may be of some help with PD. It makes sense to me. I am also on Montelukast for allergic asthma and that is under study for a similar mechanism. (MONTPARK) trials.

[LAJ12345]

it might depend what other meds you are on. St. John’s wort definitely interfere with antihistamines.