Transcript IV Drug Calculations

IV Drug Administration
Drug Calculations
November 2007
Drug Calculation Assessment
• SECTION 1: Units & Equivalences
• SECTION 2: Calculating dose as volume
• SECTION 3: Drug Strengths & Stated
Concentrations
• SECTION 4: Duration of Infusion – Stated
rate (dose per min) & Infusion rate (mL/hr)
• SECTION 5: Infusion Rate Calculations
SECTION 1:
Units & Equivalences
1 Kg =
1,000 g
1g=
1,000 mg
1 mg =
1,000 micrograms
1L=
1,000 mL
Converting from One Unit to
Another
• To convert from a larger unit to a
smaller unit, multiply by 1000 or move
the decimal point three places to the
right
• To convert from a smaller unit to a
larger unit, divide by 1000 or move the
decimal point three places to the left
Units & Equivalences
Convert 0.25 mg into micrograms
Convert 600 micrograms to mg
Answers
0.25 × 1000 or move decimal point
three places to the RIGHT
= 250 micrograms
600 ÷ 1000 or move the decimal
point three places to the LEFT
= 0.6 mg
SECTION 2: Calculating Dose as
Volume
What you WANT
X what it is IN
What you have GOT
= the volume you want to administer
A patient is prescribed 200mg of Furosemide I.V. The
ampoules available contain 250mg in 10mL. What volume
containing the drug do you need to administer?
Time
Furosemide
0700-0900

1200-1400
Dose
200mg
Route
Start Date
IV
18.05.07
End
Date
What it is IN
1600-1800
2200-2400
Other Time
Signature of
Doctor
Furosemide
250mg/10mL
P.Rescriber
What we
WANT
What we
have GOT
Answer
What you WANT
X what it is IN
What you have GOT
200 mg
250 mg × 10 mL
= 8 mL
SECTION 3: Drug Strengths &
Stated Concentrations
What you HAVE (mg)
CONCENTRATION (mg/mL)
= How much fluid is required (Volume)
A patient is prescribed 250mg of Aciclovir I.V. Aciclovir has to be
initially reconstituted with water for injection, then added to a bag
of compatible infusion fluid, giving a final concentration of
5mg/mL. How much infusion fluid should be used dilute the
reconstituted Aciclovir to achieve this final concentration?
Time
Aciclovir
0700-0900 
1200-1400 
Dose
250mg
Route
Start Date
IV
18.05.07
End
Date
1600-1800
2200-2400 
Other Time
What we
HAVE
Signature
of Doctor
Additional
Comments
P.Rescriber
Final
Concentration
5mg/mL
CONCENTRATION
Answer
What you HAVE (mg)
CONCENTRATION (mg/mL)
250mg
5mg/mL
= 50 mL
A 1% (w/v) solution means that in every 100mL of solution
you will find 1g of drug. Therefore, how many g of Glucose
would there be in 500mL of 5% Glucose?
Glucose 5%
500ml
Answer
• A 1% (w/v) solution means that in every
100mL of solution you will find 1g of drug.
100mL = 1g
Therefore a 5% w/v must mean that
100mL = 5g
Multiply each side by 5
500mL = 25g
1:10,000 strength means that in every 10,000ml of
solution you will find 1g of Adrenaline. Therefore, how
many mg of Adrenaline would there be in 10mL of
1:10,000 Adrenaline?
Answer
• 1:10,000 means that 1g of adrenaline is
dissolved in 10,000mL.
1g = 10,000mL
1000mg = 10,000mL
Divide both sides by 1000
1mg = 10mL
SECTION 4: Duration of Infusion
Stated rate (dose per min)
Infusion rate (mL/hr)
Stated Rate – dose per min
Dose (mg)
= Time
Rate (mg/min)
Furosemide must be administered at a rate no faster
than 4mg/minute. How many minutes would it take to
give 200mg of this drug?
Time
Furosemide
0700-0900

DOSE
(mg)
1200-1400
Dose
Route
Start Date
200mg
IV
18.05.07
End
Date
1600-1800
2200-2400
Other Time
Signature of
Doctor
P.Rescriber
Additional
Comments
Rate of
4mg/minute
Furosemide
250mg/10mL
Rate
(mg/min)
Answer
Dose (mg)
= Time
Rate (mg/min)
200mg
4mg/min
= 50 minutes
Infusion rate – mL/hr
Volume (mL) = Rate (mL/min)
Time (Min)
X 60 = Rate (mL/Hr)
* Tip if rate is in hours omit “X 60”
Omeprazole (Losec ®) 40mg is diluted in 100mL of
compatible infusion fluid. This infusion has to be given over
20 minutes. What rate should you set the infusion pump at,
in ml/hr, to deliver this dose?
Omeprazole
40mg/100mL
Answer
Volume (mL) = Time (mL/hr) x 60
Rate (hr)
100ml
20 mins x 60
= 300mL/hr
Acetylcysteine (Parvolex ®) 7.5g is diluted in 1000mL of
compatible infusion fluid. This infusion has to be given over
16 hours. What rate should you set the infusion pump at, in
ml/hr, to deliver this dose?
Acetylcysteine
7.5g/1000mL
Answer
Dose (mL) = Time (mL/hr)
Rate (hr)
1000
16
= 62.5 mL/hr
SECTION 5: Infusion Rate
Calculations
What you WANT x 60 (60 mins per hr)
What you have GOT
X what it is IN
= the volume you want to administer
You are required to give a patient Glyceryl Trinitrate as a
continuous I.V infusion at 25 micrograms/minute. You have
prepared a 50mg in 50mL infusion. What rate should you set the
infusion pump at, in ml/hr, to deliver this dose?
What we
Time
Glyceryl Trinitrate
07000900
What we
WANT
12001400
Dose
Route
25 micrograms/ IV
minute
60 mins
per hr
Start Date
18.05.07
End
Date
16001800
have
GOT
Glyceryl
Trinitrate
50mg/50mL
22002400
Other
Time
Signature of Doctor
P.Rescriber
Additional
Comments
Continuous
Infusion
What
its IN
Answer
What you WANT x 60 (60 mins per hr)
What you have GOT
X what it is IN
25 micrograms x 60 = 1500 micrograms/hr
1500 ÷ 1000
= 1.5 mg
1.5 mg x 50mL
50 mg
= 1.5 mL/hr
Any Questions?
Assessment time……