Chapter 10
Calculating Doses of Parenteral
Medications
Parenteral Medications
Given
–
–
–
–
intramuscularly
subcutaneously
intradermally
intravenously
Intramuscular (IM) Dosages
• Absorbed quickly
• Antibiotics, antihistamines, steroidal antiinflammatory drugs, pain medications,
immunizations
• Syringes calibrated in cubic centimeters (cc)
or milliliters (mL)
3-cc Syringe
• Numbers on syringe are in ½-mL increments;
start with ½ mL, end with 3 mL
• Each marking between numbers represents
a tenth of one mL or 0.1 mL
Figure 10-1.
3-cc Syringe
2.2 mL:
Typical Syringes
• 50-U insulin syringe (top)
• 3-cc syringe (middle)
• Tuberculin syringe (bottom)
– when dose is less than 1 cc
– calibrated to 0.01 mL
Figure 10-2.
Parenteral Medications
Formula Method
• Ordered: meperidine (Demerol) 100 mg q3–4h
IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Formula Method
• Ordered: meperidine (Demerol) 100 mg q3–4h
IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Yes
Formula Method
• Ordered: meperidine (Demerol) 100 mg q3–4h
IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Yes
• 100 mg (DO) / 50 mg (DA) x 1 mL (Qty) = dose
• 100 mg / 50 mg x 1 mL = 2/1 x 1 mL = 2 mL
• What size syringe would you choose?
Formula Method
• Ordered: meperidine (Demerol) 100 mg q3–4h
IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Yes
• 100 mg (DO) / 50 mg (DA) x 1 mL (Qty) = dose
• 100 mg / 50 mg x 1 mL = 2/1 x 1 mL = 2 mL
• What size syringe would you choose?
• 3cc
Formula Method with Reconstitution
• Ordered: methylprednisolone sodium
succinate (Solu-Medrol) 125 mg IM qd for
acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder
for injections
• Directions for reconstitution: Add 8 mL
bacteriostatic water to vial and gently agitate
until dissolved. Solution must be used within
48 hours. Dosage strength after reconstitution
is 62.5 mg/mL.
• Are the units in the same measurement?
Formula Method with Reconstitution
• Ordered: methylprednisolone sodium
succinate (Solu-Medrol) 125 mg IM qd for
acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder
for injections
• Directions for reconstitution: Add 8 mL
bacteriostatic water to vial and gently agitate
until dissolved. Solution must be used within
48 hours. Dosage strength after reconstitution
is 62.5 mg/mL.
• Are the units in the same measurement?
Yes
Formula Method with Reconstitution
• 125 mg (DO) / 62.5 mg (DA) x 1 mL (Qty) =
dose
• 125 mg / 62.5 mg x 1 mL = dose
• 2/1 x 1 mL = 2 mL
• What syringe would you choose?
Formula Method with Reconstitution
• 125 mg (DO) / 62.5 mg (DA) x 1 mL (Qty) =
dose
• 125 mg / 62.5 mg x 1 mL = dose
• 2/1 x 1 mL = 2 mL
• What syringe would you choose?
• 3 cc
Proportional Method
• Ordered: meperidine (Demerol) 100 mg q3–
4h IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Proportional Method
• Ordered: meperidine (Demerol) 100 mg q3–
4h IM for pain management
• Available: 50 mg/1 mL
• Are the units in the same measurement?
Yes
Proportional Method
• 50 mg (DA) : 1 mL (dose form) = 100 mg
(DO) : # mL (desired dose)
• 50 is to 1 as 100 is to x mL
• Answer: 2 mL
• What syringe would you choose?
Proportional Method
• 50 mg (DA) : 1 mL (dose form) = 100 mg (DO) :
# mL (desired dose)
• 50 is to 1 as 100 is to x mL
• Answer: 2 mL
• What syringe would you choose?
• 3 cc
Proportional Method with Reconstitution
• Ordered: methylprednisolone sodium succinate (SoluMedrol) 125 mg IM qd for acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder for
injections
• Directions for reconstitution: Add 8 mL bacteriostatic
water to vial and gently agitate until dissolved. Solution
must be used within 48 hours. Dosage strength after
reconstitution is 62.5 mg/mL.
• Are the units in the same measurement?
Proportional Method with Reconstitution
• Ordered: methylprednisolone sodium succinate (SoluMedrol) 125 mg IM qd for acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder for
injections
• Directions for reconstitution: Add 8 mL bacteriostatic
water to vial and gently agitate until dissolved. Solution
must be used within 48 hours. Dosage strength after
reconstitution is 62.5 mg/mL.
• Are the units in the same measurement?
Yes
Proportional Method with Reconstitution
• Ordered: methylprednisolone sodium succinate (SoluMedrol) 125 mg IM qd for acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder for
injections
• Directions for reconstitution: Add 8 mL bacteriostatic
water to vial and gently agitate until dissolved. Solution
must be used within 48 hours. Dosage strength after
reconstitution is 62.5 mg/mL.
• Are the units in the same measurement?
Yes
• What is the desired dose?
Proportional Method with Reconstitution
• Ordered: methylprednisolone sodium succinate (SoluMedrol) 125 mg IM qd for acute exacerbation of asthma
• Available: 500 mg vial of sterile white powder for
injections
• Directions for reconstitution: Add 8 mL bacteriostatic
water to vial and gently agitate until dissolved. Solution
must be used within 48 hours. Dosage strength after
reconstitution is 62.5 mg/mL.
• Are the units in the same measurement?
Yes
• What is the desired dose?
• 125 mg IM daily
Proportional Method with Reconstitution
• 62.5 mg (DA) : 1 mL (dose form) = 125 mg
(DO) : # mL (desired dose)
• 62.5 is to 1 as 125 is to x mL
• Answer: 2 mL
• What syringe would you choose?
Proportional Method with Reconstitution
• 62.5 mg (DA) : 1 mL (dose form) = 125 mg
(DO) : # mL (desired dose)
• 62.5 is to 1 as 125 is to x mL
• Answer: 2 mL
• What syringe would you choose?
• 3 cc
Subcutaneous Doses
• Water-soluble solutions (analgesics, vitamin
B12, epinephrine, certain vaccines, insulin,
heparin, anticoagulants)
• Volume typically 0.5–1.0 mL
• Maximum volume 2 mL
• May use 3mL, tuberculin or insulin syringe
Tuberculin Syringe
• 1 mL capacity
• Calibrated in hundredths of mL
Figure 10-2.
Insulin Syringe
• Holds 1/2 mL (50 units) or 1 mL (100 units)
• Only use U-100 syringe for insulin
administration
Figure 10-3.
Do Not Massage
• Heparin, insulin,
allergy injections
• Increases rate of
absorption; may
cause excessive
bleeding in heparin
injections
Calculating Units
• Ordered: penicillin G, 200,000 U IM
• Available: penicillin G, 250,000 U/mL
• Are the units in the same measurement?
Calculating Units
• Ordered: penicillin G, 200,000 U IM
• Available: penicillin G, 250,000 U/mL
• Are the units in the same measurement?
Yes
Common CNS Stimulants
• Ordered: penicillin G, 200,000 U IM
• Available: penicillin G, 250,000 U/mL
• Are the units in the same measurement?
Yes
• 200,000 U (DO) / 250,000 U (DA) x 1 mL = 0.8
mL
• What size syringe would you choose?
Calculating Units
• Ordered: penicillin G, 200,000 U IM
• Available: penicillin G, 250,000 U/mL
• Are the units in the same measurement?
Yes
• 200,000 U (DO) / 250,000 U (DA) x 1 mL = 0.8
mL
• What size syringe would you choose?
• 1 cc tuberculin or 3 cc
Mixing Insulins
• Ordered: Humulin R 22 U and Humulin NPH
26 U
• Available: 10 mL vial of U-100 Humulin R and
10 mL vial of U-100 NPH
• Are the units in the same measurement?
Mixing Insulins
• Ordered: Humulin R 22 U and Humulin NPH
26 U
• Available: 10 mL vial of U-100 Humulin R and
10 mL vial of U-100 NPH
• Are the units in the same measurement?
Yes
Mixing Insulins
• Ordered: Humulin R 22 U and Humulin NPH
26 U
• Available: 10 mL vial of U-100 Humulin R and
10 mL vial of U-100 NPH
• Are the units in the same measurement?
Yes
• What is the desired dose?
Mixing Insulins
• Ordered: Humulin R 22 U and Humulin NPH 26
U
• Available: 10 mL vial of U-100 Humulin R and
10 mL vial of U-100 NPH
• Are the units in the same measurement?
Yes
• What is the desired dose?
• Total amount of insulin is 48 U(22U + 26U = 48U)
Mixing Insulins
• What syringe would you choose?
Mixing Insulins
• What syringe would you choose?
• U-100 insulin syringe
Mixing Insulins
• What syringe would you choose?
• U-100 insulin syringe?
• How much insulin would you draw into this
syringe?
Mixing Insulins
• What syringe would you choose?
• U-100 insulin syringe?
• How much insulin would you draw into this
syringe?
• Total of 48 U (22 U of Humulin R and 26 U of
Humulin NPH)
Mixing Insulins
• What syringe would you choose?
• U-100 insulin syringe?
• How much insulin would you draw into this
syringe?
• Total of 48 U (22 U of Humulin R and 26 U of
Humulin NPH)
• What route is used?
Mixing Insulins
• What syringe would you choose?
• U-100 insulin syringe?
• How much insulin would you draw into this
syringe?
• Total of 48 U (22 U of Humulin R and 26 U of
Humulin NPH)
• What route is used?
• Subcutaneous (sc)
Intradermal (ID) Dosages
• Administered into epidermal skin layer,
above subcutaneous layer
• Volume administered—0.1 mL
• Always less than 0.2 mL
• Usually 1 mL tuberculin syringe
• Calibrated from 0.01 mL to 1 mL
• Injected in forearm, middle back
Review
•
•
•
•
Type of syringe:
Volume capacity:
Calibration:
Typically used for:
Review
• Type of syringe:
– 1 mL tuberculin
• Volume capacity:
– 1 mL
• Calibration:
– 0.01 mL
• Typically used for:
– intradermal or subcutaneous
Review
•
•
•
•
Type of syringe:
Volume capacity:
Calibration:
Typically used for:
Review
• Type of syringe:
– 3 cc
• Volume capacity:
– 3 cc
• Calibration:
– 0.1 mL and 15
/mL
• Typically used for:
– intramuscular or subcutaneous
Review
•
•
•
•
Type of syringe:
Volume capacity:
Calibration:
Typically used for:
Review
• Type of syringe:
– U-100
• Volume capacity:
– 100 units or 1 mL
• Calibration:
– 2 units
• Typically used for:
– administration of insulin only