Transcript DA-Medication-Calculations-Review

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