Dimensional Analysis and Drug Dosage Calculations Converting Units

Converting Units DIMENSIONAL ANALYSIS Changing from one unit to another unit requires: 1) Same

Conversion Factors • Mathematical Ratio of the two units you are converting • Ex:

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft 12 in

Conversion Examples • • • $12. 00 to quarters 56 yards to feet 67

Multiple Dimensions • The number of dimensions determines the number of conversions • Area

Conversions in the Denominator • Unlike numerator conversions where “what you want goes over

Conversion Examples • 55. 0 g/L to g/m. L • 25. 0 mi/hr to

Drug Dosage Calculation • Reading Drug Labels Amount and Form NDC Number Trade Name

1. Name: 1. • Trade 2. Generic Name: 3. Dosage Strength: 4. Form: 5.

Cost Comparison (Amazon. com) • Aleve: 270 tablets for $16. 40 • Naproxen Sodium:

Drug Dosage Calculations • Calculation of Oral Dosage • “po” = by mouth Ex:

Ex: Prescription Augmentin 500 mg po daily 500 mg

Ex: Prescription Augmentin 500 mg po daily 500 mg 1 tablet 250 mg

Examples 1) The order states Kantrex (antibiotic) 400 mg IM q 12 h. The

Examples The order states Kantrex 400 mg IM q 12 h. The drug is

A patient has an order for enalprilat (blood pressure medicine)0. 625 mg daily IVPB

• All the med goes into the 50 m. L. • Not calculating

Review Problem • A patient is receiving dopamine at 12 m. L/h. The concentration

Pediatric Dosage Calculation 1. Convert weight of child to kilograms. ▫ 2. 2 pounds

Examples Calculate the S&T dose range of ibuprofen for a child who weighs 36

• An infant is admitted to the hospital to rule out sepsis. The

Obstetric Dosage The physician ordered 1000 m. L D 5 W with 10 units

The physician ordered 1000 m. L D 5 W with 10 units oxytocin intravenously.

The physician has ordered 500 m. L D 5 W with 20 units oxytocin

IV + Bolus Dosage • Bolus: a larger, more concentrated dose given prior to

• The physician has ordered 1000 m. L lactated Ringer’s with 20 g

The physician order Amikacin 150 mg IM q 8 h. The following is available.

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Dimensional Analysis and Drug Dosage Calculations

Converting Units DIMENSIONAL ANALYSIS Changing from one unit to another unit requires: 1) Same type of measurement - you cannot convert length into mass 2) A conversion factor

Conversion Factors • Mathematical Ratio of the two units you are converting • Ex: Conversion of inches to centimeters • 1 inch = 2. 54 cm ▫ Possible Conversion Factors ▫ 1 in or 2. 54 cm 1 in Choose the conversion factor that puts what you are converting to over what you are converting from

Fence Post Method Covert 15. 0 ft to cm

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft 12 in 1 ft

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft 12 in 1 ft 2. 54 cm 1 in

Fence Post Method Covert 15. 0 ft to cm 15. 0 ft 12 in 1 ft 2. 54 cm = 457 cm 1 in

Conversion Examples • • • $12. 00 to quarters 56 yards to feet 67 dimes to quarters 18. 57 kg to mg 19. 84 ft to m 12 450 m. L to L • • • 48 quarters 168 feet 26. 8 quarters 1. 857 X 107 mg 6. 047 m 12. 45 L

Multiple Dimensions • The number of dimensions determines the number of conversions • Area is two dimensions (length x width) so two conversions are needed • 12. 5 m 2 to cm 2 • 25. 0 ft 3 to cm 3

Conversions in the Denominator • Unlike numerator conversions where “what you want goes over what you have”, denominator conversions are opposite = “what you want goes under what you have” • Basically, the units have to cancel the beauty of the fence post method

Conversion Examples • 55. 0 g/L to g/m. L • 25. 0 mi/hr to ft/sec • 30. 0 kg/m 2 to g/cm 2 • 0. 055 g/m. L • 36. 7 ft/sec • 3. 00 g/cm 2

Drug Dosage Calculation • Reading Drug Labels Amount and Form NDC Number Trade Name Generic Name Contraindications Storage Directions Manufacturer Dosage Strength

Drug Labels 1. Trade Name: Brand name or proprietary name 2. Generic Name: Official name of drug 3. NDC number: identifies the labeler, product, and trade package size 4. Dosage Strength: amount per unit measure 5. Form: capsule, tablet, liquid…. . 6. Route: administration pathway 7. Amount: Number of doses 8. Directions: Storage directions 9. Contraindicators: the DO NOTs of the meds

1. Name: 1. • Trade 2. Generic Name: 3. Dosage Strength: 4. Form: 5. Amount: 6. Route: 7. Directions: 8. NDC Number: 9. Contraindicators:

Cost Comparison (Amazon. com) • Aleve: 270 tablets for $16. 40 • Naproxen Sodium: 400 tablets for $13. 77

Drug Dosage Calculations • Calculation of Oral Dosage • “po” = by mouth Ex: Prescription Augmentin 500 mg po daily

Ex: Prescription Augmentin 500 mg po daily 500 mg

Ex: Prescription Augmentin 500 mg po daily 500 mg 1 tablet 250 mg

Ex: Prescription Augmentin 500 mg po daily 500 mg 1 tablet 250 mg = 2 tablets

Examples 1) The order states Kantrex (antibiotic) 400 mg IM q 12 h. The drug is supplied as 0. 5 g/2 m. L. How many m. L should be administered?

Examples The order states Kantrex 400 mg IM q 12 h. The drug is supplied as 0. 5 g/2 m. L. How many m. L should be administered? IM = q 12 h =

Examples The order states Kantrex 400 mg IM q 12 h. The drug is supplied as 0. 5 g/2 m. L. How many m. L should be administered? IM = Intramuscular q 12 h = every 12 hours

400 mg

400 mg 1 g 1000 mg

400 mg 1 g 1000 mg 2. 0 m. L 0. 5 g

400 mg 1 g 1000 mg 2. 0 m. L 0. 5 g = 1. 6 m. L Every 12 hrs

A patient has an order for enalprilat (blood pressure medicine)0. 625 mg daily IVPB (intravenous piggy back). The entralprilat is diluted to 50 m. L of D 5 W (dextrose 5% in water) and is to be infused over 20 minutes. The tubing drop factor is 60 gtt/m. L. At what rate, in drops per minute, should the IVPB be programmed?

• All the med goes into the 50 m. L. • Not calculating the dose (that is 0. 625 mg), you are calculating the rate that it is administered. • Therefore you are calculating 50 m. L in 20 minutes at a rate of 60 gtts/min. 50. 0 m. L 20. 0 min

Review Problem • A patient is receiving dopamine at 12 m. L/h. The concentration of dopamine is 200 mg in 250 m. L of 0. 9% NS. Calculate the micrograms per kilogram per minute. The patient’s weigh is 70 kg.

Pediatric Dosage Calculation 1. Convert weight of child to kilograms. ▫ 2. 2 pounds = 1 kg 2. Find the S&T (Safe and Therapeutic Dose Range) of the medicine. 3. Calculate the S&T range for the child and compare to the prescribed order.

Examples Calculate the S&T dose range of ibuprofen for a child who weighs 36 lbs. Ibuprofen is available 100 mg/5 m. L. How many m. L would you administer for the ordered dose to be S&T if that range is 5 to 10 mg/kg/dose q 6 -8 h?

Examples Calculate the S&T dose range of ibuprofen for a child who weighs 36. 0 lbs. Ibuprofen is available 100 mg/5 m. L. How many m. L would you administer for the ordered dose to be S&T if that range is 5 to 10 mg/kg/dose q 6 -8 h? 36. 0 lbs 1 Kg 2. 2 lbs = 16. 4 Kg

36. 0 lbs 1 Kg 5 m. L 2. 2 lbs 1 Kg 100 mg = 4. 1 m. L

• An infant is admitted to the hospital to rule out sepsis. The infant weighs 8 lbs and ampicillin is prescribed. Calculate the S&T 24 hour dosage range for this infant with a possible severe infection. The recommended dose is 200 to 400 mg/kg/24 h.

Obstetric Dosage The physician ordered 1000 m. L D 5 W with 10 units oxytocin intravenously. Begin at 1 m. U/min (m. U = milliunit, 1000 milliunits = 1 unit) and then increase by 1 m. U/min every 30 minutes until contraction begin. The maximum dose is 20 m. U/min. Calculate the beginning IV rate (m. L/hr).

The physician ordered 1000 m. L D 5 W with 10 units oxytocin intravenously. Begin at 1 m. U/min (m. U = milliunit, 1000 milliunits = 1 unit) and then increase by 1 m. U/min every 30 minutes until contraction begin. The maximum dose is 20 m. U/min. Calculate the beginning IV rate (m. L/hr). 1 m. U min = m. L/hr

The physician ordered 1000 m. L D 5 W with 10 units oxytocin intravenously. Begin at 1 m. U/min (m. U = milliunits, 1000 milliunits= 1 unit) and then increase by 1 m. U/min every 30 minutes until contraction begin. The maximum dose is 20 m. U/min. Calculate the beginning IV rate (m. L/hr). 1 m. U min 60 min 1 hr 1 unit 1000 m. U = m. L/hr

The physician has ordered 500 m. L D 5 W with 20 units oxytocin IV. Begin at 1 m. U/min and then increase by 1 m. U/min every 30 minutes until contraction begin. The maximum dose is 30 m. U/min. What is the initial and maximum flow rate for the IV (m. L/hr)?

IV + Bolus Dosage • Bolus: a larger, more concentrated dose given prior to the steady IV dose to help speed response time • It is also the mushy ball of chewed food that you swallow. But these are not the same thing.

• The physician has ordered 1000 m. L lactated Ringer’s with 20 g magnesium sulfate. You are to administer a bolus with 4 g/30 min, then maintain a continuous infusion at 2 g/h. 1) Calculate the IV rate (m. L/h) for the bolus order. 2) Calculate the continuous rate (m. L/h).

The physician order Amikacin 150 mg IM q 8 h. The following is available. How many m. L should be administered?