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 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 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 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 CONVERSIONS 240 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 daily Dose on Hand: 80 mg/10 ml What are you looking for?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml What is on hand?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml What did the doctor order?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Do you need any conversions?

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Begin by cross canceling labels

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Labels left should be “what you are looking for”

Order: Lasix 40 mg PO daily Dose on Hand: 80 mg/10 ml Do the math 1 2 5

What about problems with different units of measurement? Order: digoxin elixir 0.05 mg PO daily Label: Digoxin 50 mcg per ml How 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 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?