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# Drug Calculation

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Drug dose calculations
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# Drug Calculation

my latest presentation which i just recently conducted just this week in the "2nd Critical Care Course for Nurses

my latest presentation which i just recently conducted just this week in the "2nd Critical Care Course for Nurses

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### Drug Calculation

1. 1. Drug Calculation mohammed alhabsi indanan, RN
2. 2. sketch out of my talks <ul><li>Conversion </li></ul><ul><li>Methods of Calculation </li></ul><ul><li>Intravenous Flow rate Calculation </li></ul><ul><li>Continuous Infusion </li></ul><ul><li>Common Drug infusion & how they are given </li></ul><ul><li>Exercises </li></ul>
3. 3. Conversion <ul><li>Nanograms </li></ul><ul><li>Micrograms </li></ul><ul><li>Milligrams </li></ul><ul><li>Grams </li></ul><ul><li>Kilograms </li></ul><ul><li>ml </li></ul><ul><li>L </li></ul>÷ X 1000 1000
4. 4. Methods of Calculation <ul><li>Basic Formula </li></ul><ul><li>Ratio & proportion </li></ul><ul><li>Fractional Equation </li></ul>
5. 5. Basic Formula <ul><li>D = Desired dose </li></ul><ul><li>H = Dose on Hand </li></ul><ul><li>V = Vehicle-tablet or liquid </li></ul><ul><li>D </li></ul><ul><li>H </li></ul>X V = Amount to Give
6. 6. Basic Formula: <ul><li>Example: </li></ul><ul><li>Order – Dilantin 50mg orally TID </li></ul><ul><li>Drug Available-Dilantin 125mg/5ml </li></ul><ul><li>D=50mg H=125mg V=5ml </li></ul><ul><li>50 250 </li></ul><ul><li>125 125 </li></ul>x = = 2ml 5
7. 7. Ratio & proportion Extremes     Means     X : D :: V : H Desired   Known
8. 8. Ratio & proportion <ul><li>HX = DV </li></ul><ul><li> DV </li></ul><ul><li> H </li></ul><ul><li>Order-Keflex 1gm orally TID </li></ul><ul><li>Drug Available-Keflex 250mg/capsule </li></ul><ul><li>D= 1gm (note: need to convert to mg) </li></ul><ul><li>H= 250mg </li></ul><ul><li>V= 1 capsule </li></ul>= X
9. 9. Ratio & proportion: 250X = 1000 1000 250 X = X = 4 capsules X : 1000 :: 1 : 250
10. 10. Fractional Equation <ul><li>Cross multiply & solve for X </li></ul>H V = D X HX = DV = DV H
11. 11. Fractional Equation <ul><li>Order: Digoxin 0.25mg orally per day </li></ul><ul><li>Drug available: 0.125mg per tablet </li></ul><ul><li>D=0.25mg H=0.125mg V=1 tab </li></ul>0.125 1 = 0.25 X 0.125X = 0.25 X = 0.25_ 0.125 X = 2 tablets
12. 12. Intravenous Flow Rate Calculation <ul><li>Step 1- amount of fluid divided by hours to administer = ml/hr </li></ul><ul><li>Step 2- ml/hr x gtts/ml </li></ul><ul><li> 60 min </li></ul><ul><li>Amount of fluid X gtts/ml___ </li></ul><ul><li>hours to administer X min/hr </li></ul>= gtts/min Two step One step
13. 13. Intravenous Flow Rate Calculation <ul><li>1000ml over 8 hrs </li></ul><ul><li>IV set= 15gtts/ml </li></ul><ul><li>Step 1: </li></ul><ul><li>Step 2: </li></ul>1000 8 = 125ml/hr 125x15 60 = 31 gtts/min Two step
14. 14. Intravenous Flow Rate Calculation <ul><li>1000 X 15 15000 </li></ul><ul><li>8hrs X 60 480 </li></ul>= = 31 gtts/min One step
15. 15. Continuous Infusion calculation <ul><li>Note : always look 1 st for DC </li></ul><ul><li>mg/min (Lidocaine, Pronestyl) </li></ul><ul><li>Desired dose X 60 </li></ul><ul><li>Drug mg </li></ul><ul><li>Drug mg X cc/hr_____ </li></ul><ul><li>Solution cc X 60 min/hr </li></ul>= ml/hr = mg/hr
16. 16. Continuous Infusion calculation mg/min (Lidocaine, Pronestyl) 1mg = 7 cc/hr 2 mg = 15 cc/hr 3 mg = 22 cc/hr 4 mg = 30 cc/hr Lidocaine, Pronestyl 2 gms/250 cc D 5 W Rule of Thumb
17. 17. Continuous Infusion calculation <ul><li>mcg/min (For example - Nitroglycerin) </li></ul><ul><li>Desired dose X 60 </li></ul><ul><li>Drug mcg </li></ul><ul><li>Drug mcg X cc/hr____ </li></ul><ul><li>Solution cc X 60min/hr </li></ul>= cc/hr = mcg/hr
18. 18. Continuous Infusion calculation mcg/min (Nitroglycerin) 1 cc/hr = 3.3 mcg/min NTG 50 mg/250 cc 1 cc/hr = 6.6 mcg/min NTG 100 mg/250 cc Rule of Thumb
19. 19. Continuous Infusion calculation <ul><li>mcg/kg/min </li></ul><ul><li>(Dopamine,Dobutamine,Nipride etc.) </li></ul><ul><li>A. To calculate cc/hr </li></ul>
20. 20. <ul><li>mcg/kg/min </li></ul><ul><li>Dopamine 400mg/250ml D 5 W to start </li></ul><ul><li>at 5mcg/kg/min. weight is 86kg. </li></ul><ul><li>Look for Dilution Concentration… </li></ul><ul><li>400mg X 1000mcg = 400,000mcg </li></ul><ul><li> 250ml </li></ul><ul><li> = 1600mcg/ml </li></ul><ul><li>Next step: </li></ul>
21. 21. <ul><li>mcg/kg/min </li></ul><ul><li>Dopamine 400mg/250ml D5W to start </li></ul><ul><li>at 5mcg/kg/min. weight is 86kg. </li></ul><ul><li>5 X 86 X 60 </li></ul><ul><li>1600 </li></ul><ul><li>= 16.1ml/hr </li></ul>
22. 22. <ul><li>mcg/kg/min </li></ul><ul><li>Dopamine 400mg/250cc D5W to start </li></ul><ul><li>at 5mcg/kg/min. weight is 86kg. </li></ul><ul><li>250cc_ </li></ul><ul><li>400,000mcg </li></ul>X 60min X 86kg X 5mcg/kg/min = 16.1ml/hr
23. 23. Continuous Infusion calculation <ul><li>mcg/kg/min </li></ul><ul><li>B. To calculate mcg/kg/min </li></ul><ul><li>Drug mcg/ X cc/hr________ </li></ul><ul><li>Solution cc X 60min/hr X kg </li></ul>=mcg/kg/min
24. 24. Continuous Infusion calculation <ul><li>mcg/kg/min </li></ul><ul><li>Nipride 100mg/250cc D5 was ordered to </li></ul><ul><li>decrease BP. wt 143 lbs, IV pump is set at </li></ul><ul><li>25cc/hr. How many mcg/kg/min of Nipride is </li></ul><ul><li>the pt. receiving? </li></ul><ul><li>100,000mcgX25cc/hr 2,500,000 </li></ul><ul><li>250ccX 60 X 65kg 975,000 </li></ul>= = 2.5mcg/kg/min
25. 25. Continuous Infusion calculation <ul><li>How to calculate mcg/kg/min if you know the rate of infusion? </li></ul><ul><li>Dosage in (mcg/cc/min)Xrate on pump </li></ul><ul><li>Patient’s weight in kg </li></ul><ul><li>Look 1 st for dosage concentration for all drug calculation. </li></ul>=mcg/kg/min
26. 26. Look 1 st for dosage concentration for all drug calculation <ul><li>400mg of Dopamine in 250cc D 5 W </li></ul><ul><li>400,000mcg </li></ul><ul><li>250ml </li></ul><ul><li>1600mcg/ml </li></ul><ul><li>60min/hr </li></ul>=1600mcg/ml =26.6mcg/ml/min
27. 27. How to calculate mcg/kg/min if you know the rate of infusion? <ul><li>If you have a 75kg pt. for example… </li></ul><ul><li>26.6mcg/cc/min X 10ml on pump </li></ul><ul><li>Patient’s weight in kg (75kg) </li></ul><ul><li>= 3.5mcg/kg/min </li></ul>
28. 29. Common Drug infusion & how they are given 0.05 mg/kg/min Esmolol 2 - 10 mcg/min Epinephrine 1 - 20 mcg/kg/min Dopamine 2 - 20 mcg/kg/min Dobutamine 5 - 15 mg/hr Diltiazem 1 - 2 mg/min Bretylium 0.5 mg/min x 24hrs Amiodarone 5 - 15 mcg/kg/min Amrinone 0.5 - 0.7 mg/kg/hr Aminophylline Dosage Medication
29. 30. Common Drug infusion & how they are given 1-4 mg/min Procainamide 0.5 - 30 mcg/min Norepinephrine 0.1 - 5 mcg/kg/min Nitroprusside 10 - 20 mcg/min Nitroglycerin 0.5 - 1 g/hr x 24 hrs Magnesium Sulfate 30 - 50 mcg/kg/min or 2 - 4 mg/min  Lidocaine 2 - 8 mcg/min Labetalol 2 - 10 mcg/min Isoproterenol
30. 31. LET’S DO SOME EXCERCISES.. <ul><li>3 L of IV LR is charted over 12hrs. The drop factor is 15. the IV has been running for 9hrs. 800ml remains. </li></ul><ul><li>How many drops per minute are needed so that the IV finishes in the required time? </li></ul>
31. 32. LET’S DO SOME EXCERCISES.. <ul><li>The doctor has decided to intubate your 100kg patient who has gone into acute respiratory distress. As the doctor prepares to intubate, he ask you to give 2.5mg/kg of propofol (10mg/ml) IVP. How many ml of propofol will you give? </li></ul>
32. 33. LET’S DO SOME EXCERCISES.. <ul><li>A patient has daily fluid allowance of 1500ml. The patient has taken 30%. How many ml is this? </li></ul>
33. 34. LET’S DO SOME EXCERCISES.. <ul><li>A child is prescribed erythromycin. The recommended dosage is 40mg/kg/day , 4 doses daily. If the child’s weight is 15kg, calculate the size of a single dose? </li></ul>
34. 35. LET’S DO SOME EXCERCISES.. <ul><li>Dopamine 400mg in 250cc of D5W to infuse at 5mcg/kg/min. The patient’s weight is 200lbs. How many cc/hr would this be on an infusion pump? </li></ul>
35. 36. LET’S DO SOME EXCERCISES.. <ul><li>The physician orders Ampicillin 500mg q6h orally (po). Ampicillin is available: 250mg capsule (cap). How many capsules would you administer q6h? </li></ul>
36. 37. LET’S DO SOME EXCERCISES.. <ul><li>A 26 yr old man is to be given 2700ml of LR solution IV over a period of 18hrs. In addition, the amount of blood lost every 3hrs is to be replaced by packed RBC during the next 3hrs. Between the hours of 1000H & 1300H, the man lost 120ml. At what rate should fluid be delivered between 1300H and 1600H? </li></ul>
37. 38. <ul><li>MAGSUKUL…. </li></ul>