Pickar Dosage Calculation

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Pickar Dosage Calculation. Summary of Text rules. Chapter 3. Systems Of Measurements. Metric Measurements and Equivalents. Weight. Metric Measurements and Equivalents. Volume. Household System of Measurement. Apothecary Notation.

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### Pickar Dosage Calculation

Summary of Text rules

### Chapter 3

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.

### Conversions: Metric, Apothecary, and Household Systems

Chapter 4

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

Conversion
• 40 cm = ? In

40 cm  2.5 cm/in =16 in

• 32 in = ? cm

32 in x 2.5 cm/in = 80 cm

### Chapter 5

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

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

### Chapter 6

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
3 mL Syringe

Luerlock syringe hub

Plunger

Needle

Barrel

Rubber plunger tip

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.

### Chapter 8

Understanding Drug Labels

Drug Name

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
• Examples
• Refrigerate at all times
• Keep in a dry place
• Manufacturer
• Pharmacies
Expiration Date
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

### Chapter 10

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.

### Parenteral Dosage of Drugs

Chapter 11

Parenteral
• Intramuscular (IM)
• Subcutaneous (SC)
• 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 Label

Concentration

Brand Name

Storage

Manufacturer

Species

Type

Generic Name

Expiration Date

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

2. Inject

10 units of air.

• Inject 30 units of air.
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

### Reconstitution of Solutions

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

### Pediatric and Adult Weight Based Dosages

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

### Intravenous Solutions, Equipment, and Calculations

Chapter 15

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
• 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