Antihistamine loratadine busts bacterial biofilms

Not sure this has been posted here already.

Somebody said...
The common antihistamine loratadine—the active ingredient in over-the-counter medications such as Claritin, Alerclear, and Alavert—makes some species of antibiotic-resistant bacteria susceptible to antibiotics in lab experiments (ACS Infect Dis. 2019, DOI: 10.1021/acsinfecdis.9b00096). Loratadine alone also breaks up bacterial biofilms

https://cen.acs.org/pharmaceuticals/antibiotics/common-allergy-drug-makes-resistant/97/i24

I had read that before and still wonder if that is what makes me feel "off" and more symptoms when I take Claritin (10 mg). This has happened when I've been treating Lyme and also when I haven't.

thanks for sharing this Vimzor, very interesting

i had a quick look at concentrations used in the study - vs the peak concentration achievable in humans by normal dosing of loratadine ( an important bit of arithmetic to do whenever we see studies like this - if we are to understand how likely a drug used in a in-vitro experiment might be for us )

most of the study experiments used around 50uM(micro molar) of loratadine in combination with abx - and up to around 200uM of loratadine when used on its own

drugs bank says that in normal human oral use ...." the pharmacokinetic parameters of loratadine are as follows: Cmax = 2.56 ng/ml, ....." ( that's actually the fast dissolve version - which achieves a higher peak blood concentration than the standard version) - which is reached in 3 to 4hrs after ingesting
[url}https://go.drugbank.com/drugs/DB00455

now these two numbers are in different units - so to help us compare these two numbers - the study authors give the following information

50uM loratadine = 19 µg ml-1 ( see study supplemental info )

and we know there are 1000micrograms to the nanogram

and so dividing those two numbers ( after converting both to the same units ie nanograms )
gives

19,000/2.56=7,421

this means that the above study on loratadine effects on biofilm in the lab was using between 7,000 and 28,000 times higher concentrations that humans normally achieve for a few hours at peak blood concentration when taking normal doses of Claritin

please feel free to check my info / arithmetic

therefore i think the study is probably best viewed as a exploration of the mechanisms by which the loratadine might be acting - and therefore a step towards developing more potent agents that act on the same pathway - rather than any suggestion that anyone should take thousands of normal doses of Claritin ant any one time.

it probably is also worth stating that Lyme patients are often very sensitive to agent which break up biofilm or kill bacteria in any way - so its not unthinkable that some one could feel some effects from taking Claritin - after all we have plenty of members that react to a single drop of a tincture.

but, given the 3-4 orders of magnitude difference in drug concentration between human dosing and the lab experiment, its unlikely to be a game charger for us

even if you took 8 or 10 standard doses ( which i hope everyone appreciates is not likely to be very safe or a good idea ) - you are still likely to achieve only a thousandth of the blood concentration used in the lab biofilm experiments

i do not wish to pour cold water on any useful treatment - far from it - i just want to make sure people reading are able to appreciate the difference between the lab experiment - and any potential human use - as the authors of studies like this rarely advertise the extreme concentrations they are working with ( i suspect because it kind of takes the shine off the value of their work to some readers).

i hope its of some help

Hi Carl.

Not knocking what you are doing especially as its mainly to control herx.

I’ll be a little surprised if Monica E doesnt give the mouse doses used as that would be standard practice to detail in any such animal study.

But as for low doses having some non linear effect.

Actually the above study display the graphs on linear scales rather than say logarithmic or exponential ones and in them the effects of loratadine were pretty linear from 0 to 50uM ( the entire range anyone could envisage using it in)

Its also the case that we know a fair bit about how low dose naltrexone works. It basically tricks the nero endocrine system into ramping up activity.

And in the case of loratadine i think the above study was actually aimed at uncovering the mechanism and, per above, demonstrated that it was a pretty linear dose vs response effect.
So unless there is a completely different mechanism at work that we dont know about - it doesnt leave much room for some mystery low dose effect.

In my own experience many things have induced significant herx reactions and yet have not really made a significant difference in the long run.

Various tinctures where a few drops would make me ache all over and yet even after ramping up to 20x that dose i am still not fully recovered.

So it makes me wonder if herx reactions can be a reliable guide as to what's effective or not.