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Doxycycline Hydrochloride or Hyclate

Can someone tell me the difference between the two? I can't seem to find anything on Dr. Google.
It sounds like "hyclate" is just an official contraction used for "monohydrochloride hemiethanolate hemihydrate".

So I think they both mean exactly the same thing.


Senior Member
This comment explains it nicely:
When the doxycycline⋅HCl precipitates (=when it forms a solid), molecules of the solvent may get embedded in the crystal structure.

Note that this is not just a wet solid!

Hyclate is just an abbreviation for hydrochloride hemiethanolate hemihydrate, which means that each molecule of doxycycline comes with 1 ⋅HCl and 0.5 ⋅CH3CH2OH and 0.5 ⋅H2O in the crystal.

So basically, both doxycycline hydrochloride and doxycycline hyclate are pretty much the same — both are doxycycline linked on to the HCl molecule; but in the case of the latter, water and ethanol get bound up into the solid crystal as well.

(In the case of water getting bound up into crystals, this known as water of crystallization — but I did not know that ethanol can also become incorporated into the crystalline structure. And as the guy said, this is not just a wet crystal; the crystal substance will be completely dry, but water molecules get "imprisoned" inside the crystalline lattice).

Doxycycline also seems to come in other forms: doxycycline monohydrate, doxycycline carrageenate, doxycycline calcium and doxycycline phosphate. Those are chemically different from doxycycline hydrochloride Ref: 1
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