Medication Calculations Introduction to clinical calculations using DA

Calculating dosages Three steps: 1. Determine whether drug dosage desired (written order) is in the same measurement system as the drug dosage available. If not, convert between two systems. 2. Simplify by reducing to lowest terms whenever possible. 3. Calculate dosage quantity to be administered.

Conversion between systems 1. Convert to the unit used on the container or bottle so your answer is in the system of the drug to be dispensed. E.g. label is mg, order is grains, conversion from grains to mg.

Conversion between systems Several methods may be used to convert from one system to another fractions, ratios or proportions or desired over available methods. Most conversions can be done using proportion or D/A

Calculate dosage quantity to be administered Three general methods for calculating drug doses: Basic fraction method ratio and proportion. D/A x Q Select one method and use that consistently. Focus on D/A x Q

DESIRED over AVAILABLE or HAVE Method combines conversion and computation into one step. Desired units X conversion factor X quantity available Desired (caps, tabs) Have available (caps, tabs) = Q (quantity given)

Desired over available method Ordered: 10 gr Available: 300 mg tablets

Desired over available method Step 1 Set up and Convert to same equivalance 10 gr x 60 mg x 1 tab = ? 1 gr 300 mg Step 2 solve 10 x 60 x 1 = 600 = 2 tablets 1 300 300 Give two 300 mg tablets

Steps to convert one unit to another with unit equivalence Canceling unwanted units Identify the desired unit dimension or units Keep desired unit dimension in proper numerator/denominator orientation. Identify link or unit equivalence Identify unwanted dimension or units Cancel unwanted units Perform arithmetic

Choice of methods Fraction or ratio/proportion or desired over available All use same information and same format for solving problems. All do same thing. Always use method for drug calculations that makes most sense and is closest conversion to what you want to give.

Calculating oral doses Capsules, tablets or liquids Need to calculate proper drug dosage when using open stock or an individual dose (not in unit dose system) Use when drug available is in a smaller dose than that ordered. In a larger dose than that ordered. In a different unit of measure than that ordered.

Calculations Prepare a 0.6 g dose. Available 500 mg / 5 ml

ASSIGNMENTS DO WORKSHEETS- Administration of oral medications