Fundamentals of Nursing Q 374
The physician orders gr 10 of aspirin for a patient. The equivalent dose in milligrams is:
A. 0.6 mg
B. 10 mg
C. 60 mg
D. 600 mg
Correct Answer: D. 600 mg
gr 10 x 60 mg/gr 1 = 600 mg. There are 3 primary methods for the calculation of medication dosages, as referenced above. These include Desired Over Have Method or Formula, Dimensional Analysis and Ratio and Proportion (as cited in Boyer, 2002)[Lindow, 2004].
Option A: Desired over Have or Formula Method is a formula or equation to solve for an unknown quantity (x) much like ratio proportion. Drug calculations require the use of conversion factors, such as when converting from pounds to kilograms or liters to milliliters. Simplistic in design, this method allows us to work with various units of measurement, converting factors to find our answer. Useful in checking the accuracy of the other methods of calculation as above mentioned, thus acting as a double or triple check.
Option B: Units of measurement must match, for example, milliliters and milliliters, or one needs to convert to like units of measurement. In the example above, the ordered dose was in milligrams, and the have dose was in milligrams, both of which cancel out leaving milliliters (answer called for milliliters), so no further conversion is required.
Option C: The Ratio and Proportion Method has been around for years and is one of the oldest methods utilized in drug calculations (as cited in Boyer, 2002)[Lindow, 2004]. Addition principals is a problem-solving technique that has no bearing on this relationship, only multiplication, and division are used to navigate through a ratio and proportion problem, not adding.