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math calculations with preparation drugs

To process a prescription order for a 12.5% dextrose solution, the pharmacy technician would mix the stock solutions of 20% dextrose and 5% dextrose solutions in which ratio? ------------------------------------------------------------ Using the alligation method: 20 __________ 7.5 ______12.5_______ 5 ___________ 7.5 7.5 = 7.5 1 : 1 the ratio is 1 to 1

If you prepare 250 mL of a 7.5% dextrose solution using the stock solutions of 5% (D5W) dextrose and 20% (D20W) dextrose, how many milliliters (mL) of each dextrose solution will be needed? ------------------------------------------------------------ Using the alligation method: 20 __________ 2.5 _______7.5________ 5 ___________ 12.5 2.5 is the number of parts of the 20% solution. 12.5 is the number of parts of the 5% solution. 2.5 + 12.5 = 15 parts (total number of parts of the 7.5% solution) 20% dextrose solution: x / 2.5 parts = 250 mL/15 parts x = 42 mL D20W 5% dextrose solution: x / 12.5 parts = 250 mL/15 parts x = 208 mL D5W Add the volume 42 mL to the volume 208 mL in order to get to the volume of the 7.5% dextrose solution: 42 mL + 208 mL = 250 mL

Problems involving percentage of solution, ratio of solution, and ratio concentration: ------------------------------------------------------------ For percentage of solution: For weight-in-weight problems (W/W), use g / 100 g Example: 2% hydrocortisone cream means 2 g / 100 g For weight-in-volume problems (W/V), use g / 100 mL Example: 15% dextrose solution means 15 g / 100 mL For volume-in-volume problems (V/V), use mL / 100 mL Example: 50% rubbing alcohol means 50 mL / 100 mL For ratio of solution: When the pure drug is a liquid, use mL / mL Example: a 1:30 liquid solution means 1 mL / 30 mL When the pure drug is a solid or in dry form, use g / mL Example: a 1:40 drug solution means 1 g / 40 mL For ratio concentration: 1:1000 = 1 mg / mL 1:100 = 10 mg / mL 1:10 = 100 mg / mL

What is the quantity of hydrocortisone powder needed to prepare 4 oz of 2% hydrocortisone cream? ------------------------------------------------------------ 1 oz = 30 g x / 4 oz = 30 g/1 oz x = 120 g 2% means 2 g/100 g x / 120 g = 2 g/100 g x = 2.4 g = quantity

What volume of a 2% erythromycin solution can be made from 15 gm of erythromycin powder? ------------------------------------------------------------ 2% erythromycin solution means 2 g/100 mL x / 15g = 100 mL/2 g x = 750 mL = volume

How many 25 mg tablets would be needed to make 50 mL of a 10% solution? ------------------------------------------------------------ 10% solution means 10 g/100 mL x / 50 mL = 10 g/100 mL x = 5 g Now, we need to convert 5g into mg 1g = 1000mg and then 5g = 5000 mg We know that each tablet has 25 mg So, the number of tablets needed will be 5000 mg / 25 mg which is 200 tablets.

How many grams of zinc chloride are needed to prepare 1500 mL of a 1:50 solution? ------------------------------------------------------------ 1:50 solution means 1 g/50 mL x / 1500 mL = 1 g/50 mL x = 30 g 30 grams of zinc chloride

How many grams of zinc oxide are needed to prepare 75 g of a 20% zinc oxide ointment? ------------------------------------------------------------ 20% ointment means 20 g/100 g x / 75 g = 20 g/100 g x = 15 g 15 grams of zinc oxide

Mylanta and Donnatal are to be combined in a 2:1 ratio. How much of each are required to make 90 mL of the suspension? ------------------------------------------------------------ 2x + 1x = 90 3x = 90 x = 30 So, the suspension requires 30 mL of Donnatal and requires 60 mL of Mylanta.

A patient is to receive 5 mg of epinephrine. The pharmacy stocks a 1:100 solution. How many milliliters will the patient receive? ------------------------------------------------------------ 1:100 means 10 mg/ mL x / 5 mg = 1 mL/10 mg x = 0.5 mL The patient will receive 0.5 mL

A patient has a BSA of 0.75 m² and is to receive a medication with dosage based on 90 mg/m², but equally divided into two doses. How much will each dose of medication be? How many tablets will be dispensed if the medication is available in 10 mg tablets? ------------------------------------------------------------ x / 0.75 m² = 90 mg/m² x = 67.5 mg 67.5 mg/2 doses = 33.75 mg So, each dose of medication will be 33.75 mg We know that each tablet has 10mg So, the number of tablets dispensed will be 33.75 mg / 10 mg which is 4 tablets.

A patient is to receive 3 mL injection of 1:1000 epinephrine. How much of the drug will the patient receive? ------------------------------------------------------------ 1:1000 is the ratio concentration 1:1000 means 1 mg/1 mL x / 3 mL = 1 mg/1 mL x = (3mL * 1mg) / 1mL x = 3 mg The patient will receive 3 mg of the drug.

What is the infusion rate in mL/hr if you give 800 mL D5W/0.45%NS over 8 hours? (Assume 20 drops/mL) ------------------------------------------------------------ 800mL / 8hr = 100mL/hr So, the infusion rate is 100mL per hour.

Assume a 250 mL bag of an electrolyte solution runs at 12 mL/hr. How long will this bag last? ------------------------------------------------------------ 250 / 12 = 20.83 So, this bag will last a little over 20 hours at an infusion rate of 12mL per hour.

The refrigerator used for storage of pharmaceuticals must be maintained at what temperature? the refrigeration range is 2 - 5 degrees C (celsius) the refrigeration range is 35 - 40 degrees F (fahrenheit)

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