calclulation of drug dosages. determining drug dosage dosage is the amount of medication ordered to...
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Calclulation of Drug Dosages
Determining Drug Dosage• Dosage is the amount of medication ordered to be given to
the patient• If the dose on hand is the same as the MD order no
calculation is required. Example: MD orders 50 mg of medication po. The drug label reads 50 mg/tab.
• If dosage ordered is in the same unit of measurement as that on the drug label, only 1 calculation step is required. Example: The MD orders gr v of a medication po. The drug label reads gr x per tablet.
• If the dosage ordered is in a different unit of measurement than indicated on drug label then 2 calculation steps will be needed. Example: MD orders 1 g of medication po. The drug label reads 500 mg/tab.
Drug Dosage Formula
The physician orders 50 mg of medication po. The medication label reads 25 mg/tab. How much medication should be given to the patient?
The physician orders gr xv of a medication po. The medication label reads 300 mg/fluid dram. How much medication is to be given to the patient?
Parenteral Medications • Medications to be given parenterally must be
suspended in a solution• The label of the medication will indicate the amount
of drug contained in each ml of the solution• Example 10 mg/ml means there are 10 mg of
medication in each ml of solution• Some medications are ordered in units/ml• Parenteral meds are available in different dispensing
forms such as ampules, single-dose vials, and multiple-dose vials.
• Remember that 1 ml = 1 cc. It is preferred to use ml.
The physician orders 0.5 g of a medication IM. The medication label reads 250 mg/2 ml. How much medication is to be administered?
Dimensional Analysis
• Dimensional Analysis involves setting up a series of fractions.– All information is in one problem– Students do not have to remember multiple steps– Students ask four simple questions to set up their
dimensional analysis problem.
Necessities for Student Success in Dosage Calculations• Review of basic math functions – fractions
and decimals– Adding– Subtracting– Multiplication– Division
• Students must memorize equivalents
The 4 main questions
• What is the order?• What is on hand?• Do you need any equivalents?• Where are you going? (or what are you being
asked to give?)
START WITH CONVERSIONS240 mg = _____________ gr
? Gr = 1 gr X 240 mg 60 mg x
Do you have the problem set up correctly?
Cancel out the mg and multiply across
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
• What are you looking for?
ml________
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml• What is on hand?
mg
mlml
80
10?
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml• What did the doctor order?
dose
mg
1
40
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
• Do you need any conversions?
doseml
dose
mg
mg
mlml
/________
40
80
10?
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
• Begin by cross canceling labels
mldose
mg
mg
ml________
40
80
10
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
• Labels left should be “what you are looking for”
doseml
dose
mg
mg
ml
/________
40
80
10
Order: Lasix 40 mg PO dailyDose on Hand: 80 mg/10 ml
• Do the math
doseml
dose
mg
mg
ml
/________
2
1040
80
10
1
2
5
What about problems with different units of measurement?
Order: digoxin elixir 0.05 mg PO dailyLabel: Digoxin 50 mcg per mlHow many milliliters will you give?
Complex Problems• Order: Augmentin 12.5mg/kg PO every 12
hours. Child weighs 22 lbs. Pharmacy sends a 75 ml bottle of Augmentin labeled 125mg/5ml. How many milliliters will you pour from the bottle?
Physicians order Daypro 1200 mg bid.
Order: Estratab 1250mcg daily
Your patient may receive Dilaudid 3 mg IM q3h for pain. Dilaudid is supplied in 1-ml ampules containing 4 mg. How many milliliters will you administer?
The physician orders heparin 2500U subq. You have heparin, 5000U per ml. How many ml will you administer?