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 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 0700-0900  1200-1400 Dose 200mg Route IV Start Date 18.05.07 End Date 1600-1800 2200-2400 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 0700-0900  1200-1400  Dose 250mg Route IV Start Date 18.05.07 End Date 1600-1800 2200-2400  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

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 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 0700-0900  1200-1400 Dose 200mg Route IV Start Date 18.05.07 End Date 1600-1800 2200-2400 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 0700-0900 1200-1400 Dose 25 micrograms/ minute Route IV Start Date 18.05.07 End Date 1600-1800 2200-2400 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……