## Presentation on theme: "IV Drug Administration"— Presentation transcript:

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 1 g = 1,000 mg 1 mg = 1,000 micrograms 1 L = 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
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? Furosemide Time Dose 200mg Route IV Start Date End Date Other Time Signature of Doctor P.Rescriber What it is IN Furosemide 250mg/10mL EMPHASISE TO STAFF IMPORTANCE OF GIVING IV FUROSEMIDE SLOWLY AND THAT THIS DOSE WILL NORMALLY BE ADDED TO A BAG, GIVEN AS AN INTERMITTENT INFUSION WILL DISCUSS LATER ON SLIDE 11 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)

Aciclovir CONCENTRATION
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? Aciclovir Time Dose 250mg Route IV Start Date End Date Other Time Signature of Doctor Additional Comments P.Rescriber Final Concentration 5mg/mL EMPHASISE THAT INFORMATION ON CONCENTRATION WOULD BE FOUND IN THE IV MONOGRAPHS What we HAVE CONCENTRATION

Answer What you HAVE (mg) CONCENTRATION (mg/mL) 250mg 5mg/mL = 50 mL
NOW WE ARE GOING TO DISCUSS DRUG STRENGTHS

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 REMIND STAFF THAT WE WANT 500mL

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? THIS RATIO IS ONLY RELEVANT TO ADRENALINE

1g = 10,000mL 1000mg = 10,000mL Divide both sides by 1000 1mg = 10mL POSSIBLY DRAW THIS ON THE FLIPCHART

SECTION 4: Duration of Infusion Stated rate (dose per min) Infusion rate (mL/hr)
Dose (mg) = Time Rate (mg/min)

Furosemide must be administered at a rate no faster than 4mg/minute
Furosemide must be administered at a rate no faster than 4mg/minute. How many minutes would it take to give 200mg of this drug? Furosemide Time Dose 200mg Route IV Start Date End Date Other Time Signature of Doctor Additional Comments P.Rescriber Rate of 4mg/minute DOSE(mg) Furosemide 250mg/10mL INFORMATION ON RATE OF INFUSION WILL BE FOUND IN THE IV MONOGRAPHS 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

Acetylcysteine (Parvolex ®) 7
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

Glyceryl Trinitrate 50mg/50mL
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 have GOT Glyceryl Trinitrate Time Dose 25 micrograms/ minute Route IV Start Date End Date Other Time Signature of Doctor Additional Comments P.Rescriber Continuous Infusion What we WANT Glyceryl Trinitrate 50mg/50mL 60 mins per hr 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……