Amitriptyline is an old antidepressant. It's very seldom used for that purpose anymore. But it is used frequently for 'off-label' uses. One of which is treating leg pain. This is partially due to it's side effect of causing drowsiness so you can get sleep during the night and not be kept up due to leg pain.

Amitriptyline is in a class called tri-cyclic antidepressants because of it's unique chemical structure.

When it came out in the early 60's it was a great choice for patients with depression because there wasn't much out there.  But, as newer anti-depressants began showing up - particularly drugs like Prozac (fluoxetine) - they didn't have the sedation (causing you to become groggy and fall asleep) that Elavil (amitriptyline) did.  Which leads to why your doctor is probably using it to treat your leg pain. But first things first.

Off Label Use

Doctors will often use drugs for reasons other than why they were designed.  This is called an "off-label" use.  For instance, amitriptyline was originally an anti-depressant but is used for a number of different diseases now - even though it's labeling from the manufacturer doesn't indicate that.  The same is true for Neurontin® (gabapentin), Depakote® (divalproic acid) and other drugs.

A really famous example is Rogaine®.  It was originally tested as a drug to combat high blood pressure. But, during it's early use researchers discovered that while it could help with blood pressure it also had the strange side effect of causing hair growth in it's users.  Obviously, the market for men looking to grow more hair on their head is astronomical - so Rogaine® was formulated as a cream and turned into a big "off-label" hit.

But, back to why they may be using amitriptyline to treat your leg pain.

Using a Side Effect to Your Advantage

First of all, have you been diagnosed with any disease?

For example, amitriptyline has been used to treat fibromyalgia.  On the other hand, it has often been stated as a drug that may actually cause restless leg syndrome.  So, until you know exactly what your disease state is, it's hard to tell you how amitriptyline could help.  I can tell you that amitriptyline is a drug that works on your brains neurotransmitters.  Essentially raising levels of certain brain chemicals to alter mood - which is why it was originally developed as an antidepressant.  But because it can alter neurotransmitter levels it can also cause drowsiness as a side effect.

In some instances, particularly if your leg pain only occurs at night, that drowsiness effect can help you get to sleep and avoid having the pain keeping you up at night.  But keep in mind, that because of this drowsiness effect you may experience a bit of a "drug hangover" the next morning.  Meaning: you can wake up still feeling the effects of the amitriptyline by being a bit groggy and spacey for a few hours.

The good news?  You are taking a really low dose of amitriptyline.  And, in the off-chance that you find it a problem, you can split amitriptyline to give yourself only 5mg.  However, this is something you should discuss with your doctor beforehand.

About the "HCl".  I get questions a lot from patients and readers about what is printed next to the drug name on the bottle.  In your case, Amitriptyline HCl. As I mentioned above the HCl part is just the 'salt' form of amitriptyline standing for hydrochloride.  This happens all the time and is nothing to be concerned about.  And no, it doesn't mean it's a dangerous acid like hydrochloric acid.  The salt forms of the drugs are generally designed to improve the dynamics of the drug.  For example, how fast they are absorbed, broken down, etc. So don't let the HCl or anything else throw you off.  It's perfectly normal and safe.