1. Parenteral Dosage of Drugs
Chapter 11
Parenteral Dosage of Drugs

2. Parenteral Route Route of administration other than gastrointestinal
Intramuscular (IM)
Subcutaneous (subcut)
Intradermal (ID)
Intravenous (IV)

3. Parenteral Route (Continued)
Most parenteral medications are prepared in liquid form and packaged in dose vials
Ampules or prefilled syringes

4. Injectable Solutions Intramuscular maximum dosage
Average 150 lb adult = 3 mL
Maximum for deltoid site is 2 mL
Children age 6-12 years = 2 mL
Children birth to age 5 years = 1 mL

5. Three-Step Approach Step 1: Convert
All units of measurement must be in same system and all units must be in same size

6. Three-Step Approach (Continued)
Step 2: Think
Estimate logical amount
Step 3: Calculate

7. Calculation of Drug Dosage: Parenteral
Order:
Cleocin 150 mg IM q.12h
Supply:
Cleocin (clindamycin phosphate) 300 mg per 2 mL

8. Calculation of Drug Dosage: Parenteral (Continued)
Step 1: Convert
No conversion is necessary
Step 2: Think
You want to give less than 2 mL
Actually, you want to give 150 mg, which is ½ of 300 mg and ½ of 2 mL, or 1 mL
Calculate to double-check your estimate

9. Calculation of Drug Dosage: Parenteral (Continued)
Step 3: Calculate

10. Calculation of Drug Dosage: Parenteral (Continued)
Given intramuscularly every 12 hours
Select a 3 mL syringe
Measure 1 mL of Cleocin 300 mg per 2 mL
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11. Calculation of Drug Dosage: Parenteral (Continued)
Examples of parenteral dosage calculations
Collecting data about the drug
Selecting supplied dosage
Calculating the amount to give using the Three-Step Approach
Measuring the dose with appropriate equipment for medication administration

12. Calculation of Drug Dosage: Parenteral (Continued)
Order:
Robinul 150 mcg IM stat
Supply:
Robinul 0.2 mg per mL

13. Calculation of Drug Dosage: Parenteral (Continued)
Step 1: Convert
Equivalent: 1 mg = 1,000 mcg
0.2 mg = = mcg

14. Calculation of Drug Dosage: Parenteral (Continued)
Step 2: Think
Give less than 1 mL but more than 0.5 mL
Don’t be fooled into thinking 0.2 mg is less than 150 mcg
0.2 mg is more than 150 mcg
0.2 mg = 200 mcg

15. Calculation of Drug Dosage: Parenteral (Continued)
Step 3: Calculate

16. Calculation of Drug Dosage: Parenteral (Continued)
Given intramuscularly immediately
Select a 1 mL syringe
Measure 0.75 mL Robinul 0.2 mg per mL
You may have to change needles, as this is an IM injection

17. Guidelines for Syringe Selection
Standard doses more than 1 mL
Round to tenths and measure in 3 mL syringe
3 mL syringe is calibrated in 0.1 mL increments
1.53 mL is rounded to 1.5 mL
Drawn up in a 3 mL syringe

18. Guidelines for Syringe Selection (Continued)
Small (less than 1 mL), critical care, or children’s doses
Round to hundredths and measure in 1 mL syringe
1 mL syringe is calibrated in 0.01 mL increments
0.257 mL is rounded to 0.26 mL
Drawn up in a 1 mL syringe

19. Guidelines for Syringe Selection (Continued)
Amounts of 0.5 to 1 mL calculated in tenths
Can be accurately measured in either a 1 mL or 3 mL syringe

20. Remember
Dosages measured in hundredths (such as 0.83 mL) and all amounts less than mL should be prepared in a 1 mL syringe, which is calibrated in hundredths
However, if the route is intramuscular (IM), you may need to change needles to achieve a more appropriate length

21. Insulin Supply dosage of insulin is 100 units per mL
Abbreviated on label as U-100
Syringe must also be U-100
Think: U-100 = 100 units per mL
Think: U-500 = 500 units per mL

22. Insulin (Continued) Accuracy is critical
Nurses must understand and correctly interpret insulin order and label
The correct syringe must be selected

23. Combination Insulin Dosage
40 units
NPH
U-100 insulin
12 units
regular
U-100
insulin
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Total insulin dosage = 52 units

24. Preparing Combination Insulin Dosage
Inject 30 units of air
2. Inject 10 units of air
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25. Preparing Combination Insulin Dosage (Continued)
3. Withdraw
10 units regular
4. Withdraw
30 units NPH for a total of 40 units
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26. Procedure for Preparing Combination Insulin Dosage1)
Inject 30 units air 2)
Inject 10 units air 3)
Withdraw
10 units regular 4)
Withdraw
30 units NPH
for a total of 40 units
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27. Insulin Sliding Scale Order
Humulin R regular U-100 insulin subcut based on glucose reading at 1600

28. Insulin Sliding Scale (Continued)
Insulin Dose
Glucose Reading*
No coverage
Glucose less than 160
2 units
160–220
4 units
221–280
6 units
281–340
8 units
341–400
Glucose greater than 400: Hold insulin; call MD stat

29. Insulin: Avoiding Errors
Check dosage with two nurses
When combination dosages are prepared, two nurses must verify each step of the process