This lesson is going to go over the major points of what we know about the differences between doxycycline hyclate and doxycycline monohydrate. You’ll learn if they’re the same and, if not, why not.

Versions of a Drug

Did you know that when you are prescribed a drug there may be more than one version of it? And, yes, that could mean a different brand name or a different dosage form, like a capsule versus a tablet. But it could also mean it’s almost the same drug, simply a different salt of the drug.

What does that all mean? Find out as we discuss doxycycline hyclate versus doxycycline monohydrate in this lesson.

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What Is Doxycycline?

First, let’s quickly go over what doxycycline actually is. Doxycycline is a kind of antibiotic, a drug that targets bacteria, of the tetracycline class of antibiotics. It works by inhibiting protein synthesis and is thus a bacteriostatic antibiotic, one that prohibits bacteria from multiplying.

If the name doxycycline doesn’t ring a bell then maybe you know it better by one of its many brand names. This include Adoxa, Monodox, and Vibramycin.

What Is a Drug Salt?

Doxycycline comes in different salts. No, this doesn’t mean different version of table salt or the fact that it might taste salty. A salt, in pharmacology, refers to an ionisable compound that is combined with a counter-ion in order to form a neutral complex. In other words you’re taking a positively charged substance and combining it with a negatively charged substance in order to make a neutral compound. Actually, table salt is a great simple example of this:

Na(+) + Cl(-) = NaCl

That’s the basic gist of it, of course.

Taking a drug like doxycycline and converting it into a salt form, like doxycycline hyclate or doxycycline monohydrate, might increase the stability of the drug, alter the way the drug can be administered to the patient, or manipulate the way the drug interacts with the body and the body interacts with the drug, and much more.

Hyclate vs. Monohydrate

The details of what drug salts are, how they’re made, their many different types, and their many other potentially important nuances in pharmacology, therapeutics, and clinical medicine are way beyond this lesson’s scope.

What you should know for this lesson’s sake is that doxycycline hyclate and doxycycline monohydrate are two different salts of the same active drug, the latter being doxycycline itself, of course. Their main important difference is in the fact that doxycycline hyclate is water soluble. It’s easily mixable in water. In contrast, doxycycline monohydrate is only very slightly soluble in water. In other words, it doesn’t readily dissolve in water. As a result, this may alter the way each salt form of doxycycline is manufactured for use in medicine.

Their manufacture is really the only important difference between these two drugs. Clinically speaking, once both of these salt forms have been absorbed, they become the same active drug, doxycycline.

Many doctors will claim that there is no real clinical difference between the two salt forms and they are both equally effective. There is very little evidence (good evidence) to suggest they are right or wrong.

That being said, there are some who claim that doxycycline monohydrate is better tolerated than doxycycline hyclate. The reasoning being that, owing to what was said before, doxycycline monohydrate is less water soluble and will thus dissolve more slowly in the digestive tract. This, by extension, might reduce the risk of any potential gastrointestinal side-effects when taking this version of doxycycline. However, there is no good evidence for this.

One other potential consideration with respect to all of this is that patients on chronic acid suppressive therapy will have a higher gastrointestinal pH. This may decrease the bioavailability of doxycycline monohydrate. Some practitioners may recommend doxycycline hyclate in such instances as a result.

Lesson Summary

So, in essence, there’s likely no significant therapeutic difference between doxycycline hyclate and doxycycline monohydrate in most cases. They are two salt forms of the same drug, doxycycline. Doxycycline is an antibiotic, a drug that targets bacteria. It is a bacteriostatic, in that it works by prohibiting bacteria from multiplying.

The major difference between the two salt forms is that doxycycline hyclate is water soluble while doxycycline monohydrate is not as readily water soluble as the former.

Medical Disclaimer: The information on this site is for your information only and is not a substitute for professional medical advice.