Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 47

Warning: preg_replace(): The /e modifier is no longer supported, use preg_replace_callback instead in /home/ceces/public_html/wp-content/plugins/latex/latex.php on line 49
Lesson

Lesson 3: Calculating Doses

To solve for doses we use this formula:

D = Dose Order (how much the physician has ordered the patient to take)

H = Dose on Hand (how the medication is prepared by the manufacturer). For example, 10mg or 50 units.

Q = Quantity (form of drug). For example, ml, tabs, packet, etc.

Let's use the formula:

Example 1: Phenobarbital 40mg

Order (D): Phenobarbital 40mg

On Hand (H): Penobarbital 20mg per tab (Q)

D = 40mg

H = 20mg

Q = 1 tab

Cancel out units

You will give 2 tabs of Phenobarbital to the patient.

Example 2: Streptomycin 500mg Elixer

Streptomycin 500mg Elixir. The medication is available at 250mg/2ml.

D = 500mg

H = 250mg

Q = 2ml

Cancel out units

You will give the patient 4ml of Streptomycin.

Exercise

Let's put the formula to work.

Exercise 1: Order: Kelfex 500mg. On Hand: Keflex 1000mg tabs.

Answer

Order: Kelfex 500mg

On Hand: Keflex 1000mg tabs

Let's extract the information that we need to calculate a dosage in the above scenario.

D = 500 mg

H = 1000mg

Q = 1 tab

Let’s use the formula:

Cancel out units

You will give a half tab of Keflex.

Exercise 2: You receive an order for Phenobarbital 50mg. You have Phenobarbital 20mg per tablet.

Answer

Order: Phenobarbital 50mg

On Hand: Phenobarbital 20mg per tablet

D = 50mg

H = 20mg

Q = 1 tablet

Solve:

Cancel out units

You will give 2.5 tabs of phenobarbital.

Exercise 3: You receive an order for Tegretol 1.5mg per kg of body weight. The Pt weighs 72.3kg. You have Tegretol 1.25mg per ml available.

See if you can apply a weight based dose with the knowledge that you have. Remember to solve for the dose.

Answer

Order: Tegretol 1.5 mg per kg of body weight. Pt weighs 72.3kg

On Hand: Tegretol 1.25 mg per 1 ml

D =

D = Cancel out units

D =

D =

H = 1.25mg

Q = 1ml

Solve:

Cancel out units

Round to the nearest 10th

You will give 86.8ml of Tegretol.

In this next video, Sal Khan shows you how he solves complex drug dosages:

Attribution

Creative Commons License The text has been derived and modified from the "Dose Calculations" course and the "Day 3 Demonstration" by Tina Jackson and is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
Creative Commons License The video "Multiple units word problem: drug dosage (advanced)" by Sal Khan is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To see comments and other related activities please visit http://www.khanacademy.org.

Creative Commons License All other material in this work is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License. If you would like  to use this material, please provide attribution as follows: Richmond, J. (2016). https://www.ceces.ca/courses/med-math/. Continuing Education Centre for Emergency Services.

Activities Status