Medical Math

Medical Math

by BONNIE HEINRICH

​5 Rights of Medication Administration

• ​Right Patient

• ​Right Medication

• ​Right Dose

• ​Right Route

• ​Right Time

​Measurements

​Metric system

​Grams: 1 gram = 1000mg

• ​Microgram (mcg) 1000mcg = 1 mg

• ​Milligram (mg)

• ​Kilogram (kg)

​Apothecary measurement

• ​include grains, minims and drams

​

​Household measurements

• ​15 drops (gtt) = 1 mL

• ​1 teaspoon (tsp)= 5mL

• ​1 tablespoon (tbsp)= 15 mL

• ​1 fluid ounce (oz), 2 tbsp = 30 mL

• ​1 cup = 8 oz = 240 mL

• ​2.2 pounds (lb) = 1kg

​Mathematical Conversions

​A patient weighs 66 lbs, how many (X) kilograms is this?

​

​1 kg = 2.2 lb; therefore 66 lb = 66 = 30 kg

​ 2.2 lb 2.2

​OR

​ 2.2 lb. = 66 lb

​ 1 kg X lb

Cross multiply and you get the following:

​1 X 66 = 2.2 X

​66 = 2.2X

Then divide both sides of the equation by 2.2

and the results is 30 kg

​Mrs. Heinrich's Way

​1 kg : 2.2 lb : : X : 66

​

​Do the rainbow

​

​1 * 66 = 2.2 X

​66 = 2.2 X

​66 = 30 kg

​2.2

​Another Medication Calculation Example

​The dosage of a medication is 15 mL, but the patient wants to measure it in teaspoons. If 5 mL equals 1 tsp, then 15 mL equals how many (x) tsp?

​

​5 ml : 1 tsp: : 15 mL : X

​

​Do the rainbow!!

​

​5X = 15

​X = 15 X=3

​ 5

​

​Another Dosage Calculation

​ALWAYS RECHECK YOUR CALCULATIONS

​

​Dr. Smith prescribes diphenhydramine 50mg for a patient having a mild allergic reaction. Available are 25 mg capsules. How many capsules do you give?

​

​25 gm = 1 capsule

​25mg : 1 capsule : : 50 mg : X

​25 X = 50

​X= 50 x= 2 capsules

​ 25

​Error prone abbreviations

• ​MS, MSO4= morphine

• ​MgSO4 = magnesium sulfate

• Nitro = nitroglycerine

• decimal points without a leading "0" ( .5 vs. 0.5)​

• ​OD, OS, OU = right eye, left eye, both eyes

• ​AD, AS AU = right ear, left ear, both ears

• ​D/C, dc, d/c= discharge or discontinue

​Forms of medication and their routes

• ​aerosols

• ​caplets/ tablets

• ​capsules

• ​creams, drops

• ​emulsions

• ​liniments

• ​lotions/ ointments

• ​ointments

• ​patches

• ​syspensions/ syrups/ elixirs

• ​tinctures