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Serial Dilution

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Note regarding the following:  I am not a health care professional.  I am presenting my understanding of a laboratory technique, and I might be entirely wrong.  I am not advocating that you taper or discontinue medication without the care of a doctor.  This is not medical advice.


The practice of diluting medication might be useful knowledge for some on this site.  The method to which I'm referring is known as "serial dilution".  The goal of this method is to start with a known volume of a solution (in mililiters) containing a known mass (in miligrams) of medication.  Knowing this, and then knowing the concentration of your target solution will allow you to figure out how much water (or ethyl alcohol, as the case may be) must be added to the original solution to produce a target solution of a desired concentration.


The value of this approach is as an alternative to measuring small quantities of powdered or beaded medications.

If you are interested in how to do the calculations, you can search online.  Doctors are trained in this technique, so it's easiest just to ask your doctor to do the calculations for you.


Let's say we have the liquid form of a medication that contains a known amount (in mg) of the actual medication.  You can use a "graduated cylinder", which might have a capacity of 5 ml, 50 ml, 100 ml, etc. to measure out precise amounts of liquid.  Your doctor can tell you how much liquid to take, and how to properly measure liquid with a graduated cylinder.  He'll tell you about the "meniscus", etc.  If you bring your graduated cylinder and a little water to the doctor, he could show you how things are done.


Measuring liquid with a graduated cylinder becomes problematic and serial dilution becomes useful when the amounts of medication-containing-liquid become too small to be accurately measured with a graduated cylinder.  Let's say, for example, that 5 ml of a liquid contains 5 mg of a medication.  This means that 1 ml of the same liquid will contain 1 mg of a medication.  0.1 ml of the same liquid will contain 0.1 mg of the medication.  Let's say that we want to take 0.1 mg of medication.  Our graduated cylinder might not be accurate enough to reliably measure 0.1 ml.  So, what do we do?  What if we dilute our original liquid (with water, alcohol, or whatever is appropriate) so that 10 ml of a new solution contains 0.1 mg of the medication?  Then, in order to reliably measure out 0.1 mg of the medication, we don't have to try in vain to measure out 0.1 ml, we can measure out 10 ml instead.  With the original solution (the one that is concentrated), making a measurement error of just the tiniest drop will cause huge errors in our measurements.  However, this same tiny drop will cause far less of an error when using a diluted solution.


If your doctor is willing to prescribe this method of taking medication, make sure that you obtain a new, unused graduated cylinder from a reliable source.  You don't know what sorts of chemicals/medications might have been measured in a used graduated cylinder.


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