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### Pickar Dosage Calculation

### Chapter 3

### Chapter 5

### Chapter 6

### Chapter 8

### Chapter 10

### Parenteral Dosage of Drugs

### Reconstitution of Solutions

### Pediatric and Adult Weight Based Dosages

Summary of Text rules

Systems Of Measurements

Apothecary Notation

- Due to information from our clinical partners and the Board of Nursing the following rule was developed.
- We will accept documentation in the form of Roman numerals, Arabic numbers, decimals as well as fractions.

Metric Conversions

MULTIPLY to convert from a larger unit to a smaller unit, or move the decimal point to the right.

Metric Conversions

- Example: 3 L = ? mL
- THINK: Larger to Smaller: (×)
- Equivalent: 1 L = 1,000 mL
- 3 L = 3 ×1,000 or 3.000 = 3,000 mL

Metric Conversions

- DIVIDE to convert from a smaller unit to a larger unit, or move the decimal point to the left.

Metric Conversions

- Example: 400 mg = ? G
- THINK: Smaller to Larger: ()
- Equivalent: 1 g = 1,000 mg
- 400 mg = 400 1,000 or 400. = 0.4 g

Conversion

- Example

The physician ordered 125 mcg of digoxin to be given daily. Digoxin was supplied in 0.25 mg scored tablets. How many tablet(s) should be administered?

0.25mg x 1000mcg/mg = 250 mcg

Conversion Clarifications

- 1 in = 2.5 cm
- 1 cup = 240 mL
- 1 oz = 30 mL
- 1kg = 2.2 lb

We will not be using the grain (gr) measurement in our math calculations.

Conversion

- 40 kg = ? Lb

40 kg X 2.2lb/kg = 88 lb

- 66lb = ? kg

66lb 2.2 kg/lb = 30 kg

Remember you will round to tenths when needed. Example 5.23 will be rounded to 5.3

Conversions

Converting Between Traditional and International Time

- Traditional time and international time are the same hours starting with 1:00 AM (0100) through 12:59 PM (1259).
- Minutes after 12:00 AM (midnight) and before 1:00 AM are 0001 through 0059 in international time.

Converting Between Traditional and International Time

- Hours starting with 1:00 PM through 12:00 AM (midnight) are 12 h greater in international time (1300 through 2400)
- International time is designated by a unique four-digit number (colon’s are not used)

Converting Between Traditional and International Time

- Math Tip between the hours of 1:00 PM (1300) and 12:00 AM (2400), add 1200 to traditional time to find the equivalent international time; subtract 1200 from international time to convert to equivalent traditional time.

Converting Between Traditional and International Time

- Example 1

3:00 PM = 3:00 + 1200 = 1500

- Example 2

2212 = 2212 – 1200 = 10:12 PM

Addition review questions p 94

Celsius and Fahrenheit Scales

- Convert between Fahrenheit and Celsius temperatures:

Celsius and Fahrenheit Scales

- Convert 95˚ F to Celsius (First subtract 32 then divide the result by 1.8)

Celsius and Fahrenheit Scales

- Convert 35˚ C to Fahrenheit

Equipment Used in Dosage Measurement

Medicine Cup

- Medicine cup 1 fluid ounce or 30mL capacity for oral liquids.
- Calibrated to measure teaspoons and tablespoons
- Amounts less than 2.5 mL need to be measured in a smaller device, i.e. oral syringe

30 mL = 1 ounce

5 mL = 1 teaspoon

15 mL = 1 tablespoon

Calibrated Dropper

- Used to administer small quantities
- Useful in medication of children and adults and adding small quantities to liquid
- Dispense eye and ear medications

3 mL Syringe

- Calibrations read from top to the black ring of the suction plunger
- Calibrated in milliliters for each tenth
- Maximum volume administered in any one site is 3mL
- Larger volumes of medications can be delivered in divided doses or added to IV infusions or administered IV push, therefore, syringes with 5,6,10, and 12 mL may be used

Prefilled Single Dose Syringe

- Used only once and is discarded
- Discard any extra medication prior to injection

1 mL Syringe

- Also known as Tuberculin or TB syringe
- Used to administer small doses
- Calibrated in hundredths of a milliliter
- Used to give dosages of less than 0.5 mL

Units -100 Insulin Syringe

- Measurement and administration of units-100 insulin only
- Do not use with any other medications
- Syringe may be a standard units-100 or a Lo-dose units-100 for smaller doses

Safety Syringes

- The needle is protected by a shield
- Safety syringes are used to protect from injury

Needle Gauge and Length

- Needle’s gauge is it’s interior diameter. Lower the number the larger the diameter; 18-gauge needle is wider than a 22 gauge.
- The gauge depends on the viscosity (thickness) of the medication as well as the site.
- The viscous the solution and deeper injections require larger needles (lower gauge number)
- Injection site (area of tissue to be reached) will determine the length to be used.

Understanding Drug Labels

Drug Name

- Brand, trade, proprietary

Manufacturer’s name for a drug. It is usually the most prominent word on the drug label

- Generic

Established, nonproprietary name appears directly under the brand name. Sometimes it can be place inside

Brand and Generic Names

- Brand Name- Carafate
- Generic Name- Sucralfate

Dosage Strength

- Dosage weight or amount of drug provided in a specific unit of measurement
- 20 mg/ 2mL

Form

- Structure and composition of drug
- Solid forms for oral use
- Injectable
- Suppositories
- Creams
- Patches

Total Volume

- Full quantity contained in bottle or vial
- Total number of tablets or other solids
- Total fluid volume for liquids

Identify Volume

- 30 mL multiple dose vial

Label Alerts

- Warnings or special alerts
- Examples
- Refrigerate at all times
- Keep in a dry place
- Manufacturer
- Pharmacies

Expiration Date

- Check prior to administration
- Discard or return to pharmacy if expired

Lot or Control Numbers

- Important if drug is recalled
- Quickly identifies a particular group of medication packages

Controlled Substance Schedule

- Classifies drugs according to potential for use and abuse
- Schedule I – highest potential for abuse
- Schedule V – lowest potential for abuse

Other Parts of Label

- Manufacturer
- National Drug Code
- Bar Code
- Review p 138 & 139

Understanding Drug Labels

- Additional practice on page 142-148 Review set 21questions

Oral Dosage Calculations

Dosage Calculations

- Step 1 Convert

Be sure that all measurements are in the same system and all units are in the same size, converting when necessary

- Step 2 Think

Carefully consider what is the reasonable amount to administer

- Step 3 Calculate Dosage

Ordered: Flagyl 0.75 g p.o t.i.d

- You need to convert the 0.75 g to mg prior to calculating amount that you will be administering
- 0.75 g = 750 mg

Dosage Calculation

Math Tips

- When solving dosage problems for drugs supplied in tablets or capsules, Q (quantity) is always 1 because the supply dosage is per 1 tablet or capsule. Therefore, Q = 1 tablet or capsule
- The maximum number of tablets or capsules for a single dose is usually 3.

Remember

- Do not always rely on a formula.
- Always estimate what is a reasonable amount of the drug to be administered.
- This helps to identify if the dosages calculated are reasonable and sound.

Chapter 11

Parenteral

- Routes of administration
- Intramuscular (IM)
- Subcutaneous (SC)
- Intradermal (ID)
- Intravenous (IV)

Intramuscular

Maximum dosage

- Average 150 lb adult = 3 mL
- Maximum for deltoid site is 2
- Children age 6-12 years = 2 mL
- Children birth to age 5 years = 1 mL

Rounding Rule

Parenteral dosages

- Roundamount to be administered to tenths if amount greater than 1 mL . Use a 3 mL syringe
- Amounts less than 1 mL rounded to hundredths. Use a 1 mL syringe for all amounts less than 0.5 mL

Rule

Parenteral dosages

- Amounts of 0.5 mL to 1 mL calculated in tenths can be accurately measured in either a 1 mL or a 3 mL syringe

Insulin

- Supply dosage of insulin is 100 units per mL
- Abbreviated on label as U-100
- Syringe must also be U-100

Insulin

- Accuracy is critical
- Nurses must understand and correctly interpret insulin order and label
- The correct syringe must be selected

Combination Insulin Dosage

40 units

NPH

Units-100 insulin

12 units

Regular

Units -100 insulin

Total insulin dosage = 52 units

Preparing Combination Insulin Dosage

3. Withdraw

10 units regular.

4. Withdraw

30 units NPH for a total of 40 units.

Procedure for Preparing Combination Insulin Dosage

1)

Inject 30 U air

2)

Inject 10 U air

3)

Withdraw

10 U Regular

4)

Withdraw

30 U NPH

For a total of 40 U

Chapter 12

Reconstitution of Solutions

- When a fraction expresses the strength of a solution, made from a liquid concentration
- The numerator of the fraction is the number of parts of the solute.
- The denominator of the fraction is the total number of parts of the solution.
- The difference between the denominator(final solution) and the numerator (parts of solute) is the number of parts of solvent.

Reconstitution of Solutions

- Solute- a concentrated or solid substance to be dissolved or diluted.
- Solvent- is the diluent used to dissolve the solute
- Solution- the resulting mixture of a solute plus a solvent

Reconstitution of Solutions

Example ¼ strength reconstituted OJ made from canned frozen concentrate

¼ strength =1 part frozen juice concentrate

4 parts total reconstituted OJ

- 1 part -OJ concentrate (solute, numerator)
- 4 parts- total reconstituted OJ ( solution, denominator)
- 4-1 = 3 parts water (solvent)

Reconstitution of Solutions

Example 1 ⁄ 3 strength formula

- 1 part concentrate formula (solute)
- 3 parts total solution
- 3-1= 2 parts solvent (water)

Reconstitution of Solutions

- Remember to convert all fluids to the same equivalent when necessary.
- Example: Order Ensure ¼ strength 120mL for 3 feedings (Stock 4 fl oz can)
- Step 1 convert fluid to same equivalent

4 fl oz x 30mL/fl oz = 120mL ensure

concentrate

Reconstitution of Solutions

Step 2 calculate solute, solvent, and total solution

- 1 part solute(ensure) of 360 = 90 mL
- 4 parts solution ( solute and solvent)

(3 feeding of 120 mL ¼ feeding = 120 x

3= 360 mL)

- 4-1= 3 parts solvent 270mL

Chapter 14

Weight Based Dosages

- Convert child’s weight from lb.\'s to kg’s and round answer to tenths

Example

45lb ÷ 2.2 lb/kg= 20.45 rounded to 20.5

- Example

Convert 10 lb 12 oz to kg

First convert ounces to lb

12 oz ÷16 oz/lb= 12/16 = ¾ lb= 0.75 lb

10.75 lb ÷ 2.2 lb/kg = 4.88 rounded to 4.9

Weight Based Dosages

- Second step: multiply mg/kg by child’s weight in kg.
- Example

Order Morphine Sulfate 0.05 mg/kg per dose

Childs weight 35.9 kg

0.05 mg/kg/dose x 35.9 kg = 1.79 mg/dose

Rounded to 1.8 mg/dose

IV Sites

- Peripheral
- Rate of infusion should not exceed 200 mL in one hour
- Central line
- Accommodates larger concentrations and volumes of fluid

Calculation IV Flow Rate for Infusion Pump

- Regulate an IV volume by electronic infusion pump or controller calibrated in mL per hour

(rounded to a whole number)

Calculation of IV Flow Rate for Infusion Pump

- Order reads: D5W 250 mL IV over the next two hours by infusion pump

Calculation of IV Flow Rate for Infusion Pump

Step 1: Think

- Pump is set by the rate of mL per hour
- So, if 250 mL is to be infused in two hours, how much will be infused in one hour?

Calculate IV Flow Rate for Infusion Pump

- Step 2: Use the formula:

- Set pump at 125 mL per hour
- Set total volume to infuse at 250 mL

Infusion Pump Rate for less than 1 hour

(rounded to a whole number)

Infusion Pump Rate for less than 1 hour

- Order:
- Ampicillin 500 mg IV in 50 mL D5NS to infuse over 30 min via infusion pump

Infusion Pump Rate for less than 1 hour

- 50mL X 60 min/h = 100 mL/h

30 min

- Set infusion pump to infuse at 100 mL/h with an infusion volume of 50 mL

Calculation of IV Flow Rate for manual regulation: Drops per min

- Step1: Calculate infusion volume for 1h (Volume ordered ÷by number of hours to infuse) round this answer to a whole number
- Step 2: V x Drop factor= qtt/min

T

Calculation of Drops per min

- Physician orders:
- D5W IV at 125 mL per hour
- Infusion set is calibrated for a drop factor of 10 drops per mL
- Calculate IV flow rate in drops per min
- Notice that the mL cancel out, leaving drops per min

Calculation of Drops per min

1

6

- Use your watch to count drops and adjust roller clamp to deliver 21 drops per min

Calculation of Drops per min: Microdrip Drop Factor

- Order: D5W NS IV at 50 mL per h
- Drop factor is 60 drops per mL
- Notice order, 50 mL per hour, is the same as the flow rateof 50 drops per min when drop factor is 60 drops per mL

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