Drug dose calculation using measurements
- 2. A GLANCE AT MEASUREMENTS AND CONVERSIONS Dosage calculations involve measurements and conversions of the formulation, ingredients, and components of drugs. Measurements and conversions must be calculated accurately to ensure that we will be able to give the correct dosage to our patients.
- 3. Below is a table of most commonly used measurements with its corresponding conversions.
- 4. DOSAGE CALCULATION CONVERSIONS 1 liter (L) 1000 milliliters (ml) 1 ounce (oz) 30 milliliters (ml) 1 ounce (oz) 2 tablespoons (tbsp) 1 milliliter (ml) 1 cubic centimeter (cc) 1 gram (g) 1000 milligrams (mg) 1 pint 500 milligrams (mg) 1 milligram (mg) 1000 micrograms (mcg) 1 kilogram (kg) 1000 grams (g) 1 kilogram (kg) 2.2 pounds (lb) 1 inch (in) (") 2.5 centimeters (cm)
- 6. DRUG DOSE CALCULATION USING MEASUREMENTS / CONVERSIONS
- 7. Formula: Desired Dose x Volume on Hand __________________________ = amount to be given Concentration
- 8. Example 1. Doctor orders 5 mg of morphine to be administered intravenously to a patient with substernal chest pain. You have 1 ml vial that contains 10mg of morphine (10 mg/ml). How many milliliters are you going to have to draw up into a syringe and push IV into your patient’s IV line port?
- 9. What are given? Desired Dose – 5 mg of morphine IV Concentration – 10 mg Volume on Hand – 1 ml What is asked? Dosage to be given to the patient, in ml
- 10. Formula:
- 11. METRIC CONVERSIONS There are instances when we need to convert a unit of measurement to another when calculating for drug dosages. The metric system of measurements is based on a number of basic measures or units. Take a quick look at the table below. QUANTITY UNIT SYMBOL length metre m mass gram g volume litre l time second s
- 12. Large and small amounts of these units often have a prefix. Also, some common units of measurement are prefix symbol multiplication factor. PREFIX SYMBOL MULTIPLICA TION FACTOR mega m 1,000,000 kilo k 1,000 hector h 100 deka da 10 unit g, m, l, or s 1 deci d .1 centi c 0.01 milli m 0.001 micro mcg or µ 0.000001
- 13. For conversion of one metric unit to another will require us to move the decimal place to the left or to the right.
- 14. To know how many decimal places to move, follow these steps: 1. Write the metric scale. 2. Find out what the two units in the problem are. 3. Count the number of units from the given one to the desired one.
- 15. Example 1. Convert .1 decigrams to micrograms The decimal place is moved 3 places to the right using mg -- kg -- hg -- dag -- g -- dg -- cg -- mg -- mcg Therefore, 0.1 dg = 1000 mg
- 16. Example 2. Convert 250 millilitres to litres The decimal place is moved 3 places to the left ml -- kl -- hl -- dal -- l -- dl -- cl -- ml -- mcl Therefore, 250 ml = 0.250 l
- 17. Still a lot of health professionals are having difficulty with drug calculations. Is it because they don’t like Math? Before administration, some drugs require some sort of calculation and some of which requires simple to complex conversion. Don’t make life complicated. Look for the best alternative measurement system which could make all the difference and make things easy for you.