Elephant Formulary

2003-06 Susan K. Mikota DVM and Donald C. Plumb, Pharm.D.
Published by Elephant Care International - www.elephantcare.org

Milliequivalents & Molecular Weights

  

 

 

 

 

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Milliequivalents: The term milliequivalents (mEq) is usually used to express the quantities of electrolytes administered to patients. A mEq is 1/1000 of an equivalent (Eq). For pharmaceutical purposes an equivalent may be thought of as equal to the equivalent weight of a given substance. This, in practical terms, is the molecular weight of the substance divided by the valence or the radical. For example:

 

  How many milligrams are equivalent to 1 mEq of potassium chloride (KCl)?

        1. Determine the equivalent weight = gram atomic weight
                  valence

            Molecular weight of KCl = 74.5

            Valence = 1 (K+; Cl-)

            Equivalent weight = 74.5 1 = 74.5 grams

 

        2. Determine the mEq weight

            Equivalent weight 1000

            74.5 1000 = 74.5 mg = 1 mEq of KCl = 1 mEq of K+ &
                   1 mEq of Cl-
If the substance would have been CaCl2, the process would be identical using the gram molecular weight of CaCl2 (MW 111 if anhydrous; 147 if dihydrate) and a valence of 2.

 

Listed below are several commonly used electrolytes with their molecular weights and valences in parentheses:

    Sodium Chloride         58.44 (1)    Calcium Chloride 
    Sodium Bicarbonate   84 (1)               anhydrous       111 (2)

    Sodium Acetate                                   dihydrate         147 (2)

           anhydrous            82 (1)         Magnesium Sulfate

           trihydrate            136 (1)               heptahydrate   246.5 (2)

    Sodium Lactate        112 (1)                anhydrous       120.4 (2)

    Potassium Chloride    74.55 (1)    Magnesium Chloride

    Potassium Gluconate234.25(1)           anhydrous       95.21 (2)

    Calcium Gluconate    430.4 (2)            hexahydrate    203.3 (2)

    Calcium Lactate
                   (anhydrous) 218.22 (2)

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