*Calculations Flashcards
What is the formula for mmols?
Mmols = mg/MW
Diltiazem 100mg/ml drip Sig 10 mg/hr
At what rate (ml/hr) should the diltiazem drip be set to provide the prescribed dose?
10 mg/hr x 100ml/100 mg = 10 ml/hr
*Use dimensional analysis here
10/22/15. D51/2 NS 50mL/hr
Premixed bags of D51/2 NS (1 liter) are available on the floor. The patient’s infusion is started at 1300 the day it was ordered. On what day and time will the pre-mixed bag run out?
50mL/1 hr x 1000ml/x hr = 20 hrs
Answer: 10/23 at 0900
How many mL is in a tsp (t)?
5 mL
How many mL is in a tbsp (T)?
15 mL
How many mL are in 1 ounce (oz)?
30mL
How many cm are in 1 inch?
2.54 cm
How many mg are in a grain (gr)?
65 mg
What is the definition of kilo?
1,000, as in kg
What is the definition of deci?
1/10, as in dL
What is the definition of milli?
1/1,000, as in mL
What is the definition of micro?
1/1,000,000 as in mcg
What is the definition of nano?
1/1,000,000,000 as in ng
If 200 capsules contain 500 mg of an active ingredient, how many milligrams of the active ingredient of 76 capsules contain?
200 caps/ 500mg = 76 caps/ x mg
Answer: 190 mg
If one 10ml vial contains 0.05 g of diltiazem, how many milliliters should be administered to provide a 25 mg dose of diltiazem?
Milli = 1/1000
0.05g x 1,000 mg = 50 mg
Now calculate the number of mL for a 25 mg dose
50mg/10mL = 25mg/ x mL
Answer: 5 mL
How many ounces AND mL are in one pint?
16 ounces and 473 mL
His phenobarbital elixir contains 18.2 mg of phenobarbital per five ML, how many grams of phenobarbital would be used in preparing a pint of the elixir? Round to the nearest 10th.
First convert milligrams to grams
- 2mg/x g = 1000mg/1g. 0.0182g
- 0182g/ 5 mL = x g/ 473 mL
Answer: 1.7 g
Digoxin injection is supplied in ampules of 500 µg (mcg) per 2 mL. How many milliliters Musta nurse administer to provide a dose of open. 2 mg? Round to the nearest 10th.
First convert 500 µg to milligrams
500mcg x 1mg/1,000mcg = 0.5 mg
0.5mg/2 mL = 0.2mg /x mL. X= 0.8mL
How many micrograms are in 1 mg?
1,000
A cough syrup contains 4 grams of brompheniramine maleate per liter. How many milligrams are contained in a teaspoon full dose of the elixir?
First convert grams to milligrams
4 g x 1000mg / 1g = 4,000 mg per 1 liter
1tsp =5 mL
4,000mg/1,000mL = x mg/5 mL. X=20
In elixir of Ferrous sulfate contains 220 mg the Ferrous sulfate for 5 mL. If each milligram the Ferrous sulfate contained the equivalent of 0.2 mg of elemental iron, how many milligrams of elemental iron would be in each 5 mg of elixir?
0.2 mg Fe/ 1 mg FeSO4 = xmg Fe/ 220 FeSO4. X= 44 mg of elemental Fe
What percentage of elemental iron is contained in Ferrous sulfate (FeSO4)?
20%
Sig: i-ii tabs PI q 4-6 hrs prn pain x 2 days. NTE 6/d
How many tablet should be dispensed?
12 tablets
Note NTE = not to exceed
The pharmacist prescription for Vigamox .5%.
Dispense 3 mL. 1 gtt tid ou x 7d.
How many drops will the patient use per day?
Six drops
Note that the patient is using in both eyes and the questions only asking for one day
A seven-year-old male child (3 feet, 4 inches and 48 pounds) presents to the urgent care clinic with a fever of 102°F, and nausea vomiting that begin the previous day. He will receive and acetaminophen five grain suppository for the fever. The pharmacist received a prescription for the suppository with the instructions: 1 PR Q4-6H pen temp >102 degrees. How many mg/kg willthe child receive per dose? Round to the nearest whole number.
One grain equal 65 mg
1gr/65mg = 5 gr/x mg. X =325mg
48 lb / 2.2 = 21.8 kg
325 mg/ 21.8kg = 15 mg/kg
What is the recommended weight-based acetaminophen dosing for children under 12 years of age?
10 to 15 mg/ kg Q 4 to six hours
What does the abbreviation ac mean?
Before a meal
How many milliliters of Mylanta suspension or contained in each dose of the prescription below? Round to the nearest whole number
Belladonna tincture 10ml
Phenobarbital 60mL
Mylanta susp. as. ad. 120mL
Sig: 5 mL BID
The total prescription is 120 ML; 10 mL belladonna, 60 mL of phenobarbital, and that leaves 15 amount for the Mylanta.
50mL Mylanta/120 mL total RX = XML Mylanta/ 5 mL total RX dose.
X = 2 mL Mylanta per dose
A pharmacist will prepare and Amoxil suspension to provide 1600 mg daily dose for a child. The dues will be divided be BID. To prepare Amoxil containing 200 mg/5 ML the pharmacist should add 76 ML of water for a final volume of 100mL. The pharmacist accidentally added too much water in the final volume is 110 ML. How many ML should the patient take twice daily to receive the correct dose?
200mg/5mL = xmg/100 mL X= 4,000mg
4,000mg/110mL = 800mg/x mL
X=22mL
How many mg codeine will be contained in each capsule?
Codeine. 0.6g Guaifenesin. 1.2g Caffeine. 0.15g M. ft. Caps. No 24 Sig: one capsule TID PRN cough
Begin by converting to the units requested an answer (mg)
0.6g codeine x 1,000mg/1g = 600 mg codeine for the entire prescription
The prescription order is for 24 capsules
600mg codeine total/24 caps = 25 mg codeine/ capsule
Physician write an order for Aminophylline 500 mg IV, dosed at 0.5 mg per kilogram per hour for a patient weighing 165 pounds. There is only theophylline in stock. How many milligrams of theophylline will the patient received per hour? Round to the nearest whole number
Aminophylline to theophylline: multiply by 0.8
Theophylline to Aminophylline: divide by 0.8
Use dimensional analysis
0.5mg/1kg | 75kg/1hr = 37.5 mg/HR Aminophylline
37.5 mg/HR Aminophylline x 0.8 = 30 mg/HR theophylline
How many grains aspirin will be contained in each capsule? Round to the nearest tenth
aspirin. 6g Phenacetin.3.2g Caffeine. 0.48g M. ft. No. 20 caps sig: One capsule Q6H PRN pain
65mg =1 grain
6000mg/Xgrid = 65mg/1 gr X = 92.3 grains
92.3 grains/20 capsules = 4.6 grains/capsule
A metered dose inhaler provides 90 micrograms of albuterol sulfate with each inhalation. The canister provides 200 inhalations. If the patient uses the entire canister, how many total milligrams will the patient have received?
90mcg | xmg/1000 mcg = 0.09mg per inhalation
0.09mg/1 inhalation = x mg/ 200 inhalations
Answer 18 mg
What is the definition of percent weight in volume (% w/v)?
g/100 mL (A solid mixed into a liquid)
What is the definition for percent volume in volume (% v/v)?
mL/100 mL (A liquid mixed into a liquid)
What is the definition of percent weight in weight (%w/w)?
g/100g (A solid mixed into a solid)
How many grams of NaCl are in 1 liter of normal saline (NS)?
Normal saline (NS) is 0.09% (w/v) NaCl solution. Remember w/v is always expressed as grams per 100 ML, therefore NS contains 0.9 g NaCl per 100mL of solution
0.9g/100 mL = Xg /1,000 mL X=9g
How many grams of NaCl are in 500mL of 1/2NS? Round to the nearest hundredth.
0.45g/100mL = xg/500mL. X= 2.25g
How many grams of dextrose are in 250 mLs of D5W? Round to the nearest tenth.
D5 W refers to 5% (w/v) dextrose and water solution
5g/100mL = xg/250mL. X= 12.5g
If 1250 g of a mixture contains 80 g of drug, what is the percentage strength (w/w) of the mixture? Round to the nearest tenth.
80g/1250g = Xg/ 100g
X= 6.4g, which is 6.4%
A mouth rinse contains 1/12% (w/v) of chlorhexidine gluconate. How many grams of chlorhexidine gluconate should be used to prepare 18 L of mouth rinse? Round to the nearest whole number.
1/12% = 0.083g per 100mL (w/v)
18L x 1,000mL/L = 18,000mL
0.083g / 100mL = xg/ 18,000 mL
X= 14.94g, rounded to 15 g
A pharmacist at 5.3 g of hydrocortisone to 150 g of a 2.5% hydrocortisone ointment. What is the percentage (w/w) of hydrocortisone in the finished product? Round to the nearest whole number.
First determine the amount of hydrocortisone in the current product.
- 5g HC / 100g = xg HC/150g. X=3.75hc
- 3 g of hydrocortisone is being added to the existing product which contains 3.75 g of hydrocortisone: 5.3g +3.75g =9.05g
9.05 g hc/ 155.3g ointment = xg hc/ 100g oint.
X= 5.8274 g, rounded to 6%
How many milliliters of a hydrocortisone liquid (40mg/mL) Will be needed to prepare 30 g of an 0.25% cream (w/w)? Rounded to the nearest hundredth.
First calculate the amount of Hydrocortisone needed in the final product
0.25g/100g = xg/30g X= 0.075 g or 75 mg
Then solve for ML of Hydrocortisone liquid needed
40mg/ML = 75mg/xmL
X= 1.875 mL, reindeer to 1.88mL
