Medication Calculations Drug Dosages n Drug Dose Formula

Medication Calculations

Drug Dosages n Drug Dose Formula Dx. Q= A ¨D = dose ordered ¨A = dose available (or H for on Hand) ¨Q = quantity dose available in

Drug dose formula n Proportion formula: ¨ Dose available = ¨ Amount available Dose desired Amount needed

Nonparenteral n Lactulose 1500 mg ordered. Available medication is 10 g/10 m. L. How many m. L will you give? n Ambien 10 mg ordered. Available medication is available in 0. 005 g tablets. How many will you give? n Cipro 750 mcg po bid for sinusitis. Supplied in 0. 75 mg/tablet. How many will you give?

Nonparenteral n Lactulose 1500 mg ordered. Available medication is 10 g/10 m. L. How many m. L will you give? 1500/10000 X 10= 1. 5 m. L ¨ Or n Ambien 10 mg ordered. Available medication is available in 0. 005 g tablets. How many will you give? 10 mg/5 mg = 2 tablets ¨ or n 1. 5 g/10 g x 10= 1. 5 m. L 0. 01 g/0. 005 g= 2 tablets Cipro 750 mcg po bid for sinusitis. Supplied in 0. 75 mg/tablet. How many will you give? ¨ 750 mcg/750 mcg = 1 tablet ¨ Or 0. 75 mg/0. 75 mg= 1 tablet

Nonparenteral – proportions Lactulose: n 10 g = 1500 mg 10 ml x ml n 10000 mg = 1500 mg 10 ml x ml n 10000 x = 15000 n X=1. 5 ml n Ambien: n 0. 005 g = 10 mg 1 tab x tab n 5 mg = 10 mg 1 tab x tab n 5 x = 10 n X=2 n Now, try the Cipro problem on your own using proportions

Nonparenteral n Wellbutrin 100 mg po for smoking cessation. Medication supplied in 200 mg tablets. How many will you administer? n Synthroid 400 mcg po qdaily for hypothyroidism. The medication is supplied in 0. 2 mg/tablets. How many will you give? n Acetaminophen 600 mg po every 4 -6 hours for temp >101 F. Supplied in gr X tablets. How many tablets will the nurse administer?

Calculating m. L/hr n 750 m. L of D 5 ¼ NS w/ 20 meq is ordered to be given over an 3 hrs 15 minutes. n 1. 5 L of 1/4 NS with 2 amps of bicarb is to be given over 7 1/2 hours. n 0. 75 L over 120 minutes

Calculating m. L/hr n 750 m. L of D 5 ¼ NS w/ 20 meq is ordered to be given over an 3 hrs 15 minutes. 750 m. L = 230. 76 or 231 m. L/hr 3. 25 hrs n 1. 5 L of 1/4 NS with 2 amps of bicarb is to be given over 7 1/2 hours. ¨ n First convert liters to m. L, 1000 m. L in liter so 1. 5 L = 1500 m. L= 200 m. L/hr 7. 5 hrs 0. 75 L over 120 minutes Again, convert liters to m. L so 0. 75 L = 750 m. L ¨ Second convert minutes to hours 120 minutes = 2 hrs 750 m. L= 375 m. L/hr 2 hrs ¨

Calculating m. L/hr n 3 quarts over 10 hours. Calculate m. L/hr n 2000 m. L of D 5 NS over 180 minutes. Calculate m. L/hr. n 1. 5 L of D 51/4 NS over 4 hours. Calculate m. L/hr.

Calculating m. L/hr n 3 quarts over 10 hours. Calculate m. L/hr First: 3 qts = 3 L, convert liters to m. L: 1000 m. L= 1 L so 3 L = 3000 m. L = 300 m. L/hr 10 hrs n 2000 m. L of D 5 NS over 180 minutes. Calculate m. L/hr. First convert minutes to hours: 180 min = 3 hrs 2000 m. L = 666. 66 or 667 m. L/hr 3 hrs n 1. 5 L of D 51/4 NS over 4 hours. Calculate m. L/hr. First convert liters to m. L: 1. 5 L = 1500 m. L= 375 m. L/hr 4 hrs

m. L/hr n Ampicillin 1. 5 g in 100 m. L over 45 minutes ¨ how n many m. L/hr? Zosyn 2 g in 250 m. L over 3 hrs 15 minutes ¨ How many m. L/hr?

m. L/hr n Ampicillin 1. 5 g in 100 m. L over 45 minutes ¨ how many m. L/hr? First, think about what you need from this equation: all you need is volume in m. L and time in hours (so 45 minutes is 0. 75 hrs) 100 m. L = 133. 33 m. L/hr 0. 75 hrs n Zosyn 2 g in 250 m. L over 3 hrs 15 minutes ¨ How many m. L/hr? ¨ Need volume in m. L (250 m. L) and time in hrs so 3. 25 hrs 250 m. L= 76. 9 or 77 m. L/hr 3. 25

FORMULA: DROPS/MIN Volume in m. L x Drop Factor = gtt/min time in minutes i. e. 1000 m. L over 8 hours with a drop factor (tubing size) of 15 drops/ m. L 1000 (volume) x 15 (drops/m. L) = 31. 25 drops (gtts)/min 480 minutes

Calculating Drops per Min n 75 m. L over 0. 5 hr with a drop set (tubing size) of 15 drops /m. L n 450 m. L over 25 minutes with a microdrip tubing set n ½ qt over 3 hrs with a drop set of 10 drops/m. L n 550 m. L over 1. 25 hrs with a drop set of 60 drops/m. L

Calculating Drops per Min n 75 m. L over 0. 5 hr with a drop set (tubing size) of 15 drops /m. L First, what do you need: volume in m. L (75 m. L), time in minutes (30 min), and drop factor (15) 75 m. L x 15 =37. 5 gtt/min 30 min n 450 m. L over 25 minutes with a microdrip (microdrip is always 60 gtts/m. L, macro can be 10, 15 or 20 gtts/m. L) tubing set 450 m. L x 60= 1080 gtts/min 25 min n ½ qt (1 qt is equivalent to one liter, which is = 1000 m. L) over 3 hrs with a drop set of 10 drops/m. L First convert qts to m. L= 500 m. L, then 3 hrs to minutes 180 min 500 m. L x 10 = 27. 77 or 28 gtts/min 180 min n 550 m. L over 1. 25 hrs with a drop set of 60 drops/m. L 550 m. L x 60 = 440 gtts/min 75 min

Calculating Drops per minute n 1000 m. L 09%NS at 200 m. L/hr for dehydration. Calculate flow rate in gtts/min (tubing: 10 gtts/m. L). n Ampicillin 1 g in 100 m. L of D 5 W IVPB to infuse over 20 minutes. Calculate the flow rate in gtts/min (tubing: 15 gtts/m. L) n 2. 5 L to infuse over 4 hours. Calculate flow rate in gtts/min (tubing: 60 gtts/m. L)

Calculating Drops per minute n 1000 m. L 09%NS at 200 m. L/hr for dehydration. Calculate flow rate in gtts/min (tubing: 10 gtts/m. L). First, it already gives you m. L/hr so have to use that: 200 m. L/hr so 200 m. L, 60 min, drop factor 10 200 m. L x 10 = 33. 33 or 34 gtts/min 60 min n Ampicillin 1 g in 100 m. L of D 5 W IVPB to infuse over 20 minutes. Calculate the flow rate in gtts/min (tubing: 15 gtts/m. L) First fine volume: 100 m. L, then time in minutes 20, the drop factor 15 100 m. L x 15 = 75 gtts/min 20 min n 2. 5 L to infuse over 4 hours. Calculate flow rate in gtts/min (tubing: 60 gtts/m. L) First convert liters to m. L (2. 5 L = 2500 m. L) then convert time to min (4 hrs= 240 min), the drop factor is 60 (microdrip) 2500 m. L x 60 = 625 gtts/min 240 min

Drops per minute (gtts/min) n 1, 000 m. L D 5 0. 33%NS in 6 hours. The drop factor is 15 gtt/m. L. Determine drops per minute n Vancomycin 500 mg IVPB (reconstituted 50 mg/ml) 100 m. L D 5 W to infuse over 1 hr drop factor 15 gtt/m. L ¨ Determine rate in gtt/min to be infused

Drops per minute (gtts/min) n 1, 000 m. L D 5 0. 33%NS in 6 hours. The drop factor is 15 gtt/m. L. Determine drops per minute ¨ First find volume in m. L (1000 m. L) , convert time to minutes (6 x 60= 360 minutes), drop factor 15 ¨ n 1000 m. Lx 15 = 41. 66 or 42 gtts/min 360 min Vancomycin 500 mg IVPB (reconstituted 50 mg/ml) 100 m. L D 5 W to infuse over 1 hr drop factor 15 gtt/m. L ¨ Determine rate in gtt/min to be infused ¨ First, find volume in m. L (100 m. L), then time in minutes (1 hr= 60 min), drop factor 15 100 m. L x 15 = 25 gtts/min 60 min

Formula: Critical Care (mcg/kg/min) n To Calculate m. L/hr: Ordered mcg/kg/min x patient’s weight in kg x 60 min ________________________ Medication concentration (# of mcg/1 m. L) i. e. dopamine 10 mcg/kg/min, patient weighs 50 kg, dopamine available in 2 g in 250 m. L of 0. 9% NS First, fill in top numbers 10 mcg/50 kg/60 min Then convert 2 grams into mcg for denominator (there are 1, 000 mcq in one gram so 2 g= 2, 000 mcg) 10 mcg x 50 kg x 60 min x 250 m. L 2, 000 mcg = 3. 75 m. L/hr

Critical Care n Dobutamine 12 mcg/kg/min ¨ Pt weighs 75 kg ¨ Concentration 1 n g in 250 m. L of D 5 W Neosynephrine 5 mcg/kg/min ¨ Pt weights 80 kg ¨ Concentration 2 g in 250 m. L of D 5 W

Critical Care n Dobutamine 12 mcg/kg/min ¨ Pt weighs 75 kg ¨ Concentration 1 g in 250 m. L of D 5 W First plug in numbers 12 mcg x 75 x 60 min Then convert 1 g to mcg = 1, 000 mcg 12 mcg x 75 kg x 60 min 1, 000 mcg n x 250 m. L = 13. 5 m. L/hr Neosynephrine 5 mcg/kg/min ¨ Pt weights 80 kg ¨ Concentration 2 g in 250 m. L of D 5 W Plug in numbers 5 mcg/80 kg/60 min Then convert 2 g to mcg = 2, 000 5 mcg x 80 kg x 60 min 2, 000 mcg x 250 m. L= 3 m. L/hr

Critical Care n Propofol 30 mcg/kg/min. Pt weighs 75 kg. Propofol concentration is 15 mg/m. L. How many m. L/hr should you program the pump for? n Nitroprusside 3 mcg/kg/min ordered. Pt weighs 70 kg. Available solution is 50 mg in 250 m. L. How many m. L/hr should you program the pump for?

Critical Care n n n Propofol 30 mcg/kg/min. Pt weighs 75 kg. Propofol concentration is 15 mg/m. L. How many m. L/hr should you program the pump for? First plug in numbers 30 mcg/75 kg/60 min Then convert 15 mg to mcg = 15, 000 mcg 30 mcg x 75 kg x 60 min x 1 m. L= 9 m. L/hr 15, 000 mcg n Nitroprusside 3 mcg/kg/min ordered. Pt weighs 70 kg. Available solution is 50 mg in 250 m. L. How many m. L/hr should you program the pump for? Convert mg to mcg = 50, 000 mcg n 3 mcg x 70 kg x 60 min x 250 m. L=63 m. L/hr 50, 000 mcg

Critical Care n Nitroglycerin at 10 mcg/min. Concentration available is 100 mg in 500 m. L of D 5 W. How many m. L/h should the IV be programmed for? n Levophed ordered at 10 mcg/min. Concentration available is 2 mg/250 m. L. How many m. L/hr should you program the pump for?

Critical Care n Nitroglycerin at 10 mcg/min. Concentration available is 100 mg in 500 m. L of D 5 W. How many m. L/h should the IV be programmed for? Plug in numbers: 10 mcg/60 min, convert 100 mg to mcg for denominator = 100, 000 mcg 10 mcg x 60 min x 500 m. L= 3 m. L/hr 100, 000 mcg n Levophed ordered at 10 mcg/min. Concentration available is 2 mg/250 m. L. How many m. L/hr should you program the pump for? Convert 2 mg to mcg (2, 000 mcg) 10 mcg x 60 min x 250 m. L= 75 m. L/hr 2, 000 mcg

Calculating mg/hr to m. L/hr Using basic formula: D/A x V = Dose ordered (mg/hr) X volume = Dose Available (amount of on hand) i. e. 500 mg in 500 m. L. MD orders 50 mg/hr x 500 m. L= 50 m. L/hr 500 mg

Drip Rates (converting mg/hr to m. L/hr) n 225 mg of Dilantin in 100 m. L of NS. The infusion must be set at 15 mg/hr. What is rate m. L/hr? n 75 mg of ampicillin in 125 m. L of Dextrose. The infusion must be set at 10 mg/hr. What is the rate m. L/hr? n 500 mg of Vancomycin in 1000 m. L of Dextrose. The infusion must be set at 125 mg/hr. What is the rate m. L/hr?

Drip Rates (determining mg/hr to m. L/hr) n n n 225 mg of Dilantin in 100 m. L of NS. The infusion must be set at 15 mg/hr. What is rate m. L/hr? USE D x Q = formula for these A Doctor orders 15 mg/hr, what is available: 225 mg/100 m. L 15 mg/hr x 100 m. L= 6. 66 m. L/hr or 7 m. L/hr 225 mg n 75 mg of ampicillin in 125 m. L of Dextrose. The infusion must be set at 10 mg/hr. What is the rate m. L/hr? Dr. orders 10 mg/hr, available: 75 mg/125 m. L 10 mg/hr x 125 m. L = 16. 66 or 17 m. L/hr 75 mg n n 500 mg of Vancomycin in 1000 m. L of Dextrose. The infusion must be set at 125 mg/hr. What is the rate m. L/hr? 125/500 x 1000= 250 m. L/hr

Determining mg/hr to m. L/hr n 125 mg of cardizem in 250 m. L of NS. The infusion must be set at 20 mg/hr. What is rate m. L/hr? n 750 mg of vancomycin in 500 m. L of Dextrose. The infusion must be set at 50 mg/hr. What is the rate m. L/hr? n 200 mg of Acyclovir in 250 m. L of Dextrose. The infusion must be set at 5 mg/hr. What is the rate m. L/hr?

Determining mg/hr to m. L/hr n 125 mg of cardizem in 250 m. L of NS. The infusion must be set at 20 mg/hr. What is rate m. L/hr? 20 mg/hr x 250 m. L= 40 m. L/hr ¨ 125 mg n 750 mg of vancomycin in 500 m. L of Dextrose. The infusion must be set at 50 mg/hr. What is the rate m. L/hr? 50 mg/hr x 500 m. L=33. 33 m. L/hr 750 mg n 200 mg of Acyclovir in 250 m. L of Dextrose. The infusion must be set at 5 mg/hr. What is the rate m. L/hr? 5 mg/hr x 250 m. L= 6. 25 m. L/hr ¨ 200 mg

Units per hour to m. L/hr n Heparin 1000 Units/hr ¨ n Insulin 8 units/hr ¨ n Concentration 25, 000 Units in 250 m. L 0. 9% NS Concentration 100 units in 250 m. L/NS Heparin 8 units/kg/hr ¨ Concentration 5, 000 units in 100 m. L 0. 9% NS. Wt 60 kg.

Units per hour to m. L/hr USE D/A x Q formula for these too. n Heparin 1000 Units/hr Concentration 25, 000 Units in 250 m. L 0. 9% NS 1000 u/hr x 250 =10 m. L/hr 25, 000 units ¨ n Insulin 8 units/hr Concentration 100 units in 250 m. L/NS 8 units/hr X 250 m. L= 20 m. L/hr 100 units ¨ n Heparin 8 units/kg/hr ¨ ¨ Concentration 5, 000 units in 100 m. L 0. 9% NS. Wt 60 kg. (8 units x 60 kg = 480) 480 units x 100 m. L= 9. 6 m. L/hr 5000 units

Converting m. L/hr to units/hr or mg/hr n 40 units of Regular insulin in 100 m. L 0. 9% NS to infuse at 10 m. L/hr ¨ How many units will be delivered per hour? ¨ Can use proportion: n 40 units: 100 m. L : : X units: 10 m. L ¨ 100 x = 400 units ¨ 400/100= 4 units/hr ¨ Or can determine how many units per m. L n 40/100=0. 4 then multiply by rate i. e. 10 x 0. 4= 4 units hour

Converting m. L/hr to mg/hr n Morphine is infusing at 15 m. L/hr. Concentration is 100 mg/200 m. L. How many mg/hr is patient receiving? n Dilantin is infusing at 20 m. L/hr. Concentration is 50 mg/250 m. L. How many mg/hr is patient receiving?

Converting m. L/hr to mg/hr n Morphine is infusing at 15 m. L/hr. Concentration is 100 mg/200 m. L. How many mg/hr is patient receiving? ¨ 100 mg: 200 m. L: : X mg: 15 m. L ¨ 200 x =1500 (so 1500/200= 7. 5 mg/hr) n Dilantin is infusing at 20 m. L/hr. Concentration is 50 mg/250 m. L. How many mg/hr is patient receiving? 50 mg: 250 m. L : : Xmg: 20 m. L= ¨ 250 X = 1000 (so 1000/250 = 4 mg/hr)

m. L/hr to mg/hr n 800 mg in 500 m. L D 5 W at rate of 30 m. L/hr ¨ How n many mg/hr is patient receiving? Heparin is infusing at 8 m. L/hr. Concentration is 25, 000 units/250 m. L. ¨ How many units is he receiving each hour?

m. L/hr to mg/hr n 800 mg in 500 m. L D 5 W at rate of 30 m. L/hr ¨ How many mg/hr is patient receiving? 800 mg: 500 m. L : : x mg: 30 m. L 500 x: 24000= (so 24000/500= 48 mg) n Heparin is infusing at 8 m. L/hr. Concentration is 25, 000 units/250 m. L. ¨ How many units is he receiving? 25000 units: 250 m. L: : X units: 8 m. L 250 X: 200000= (so 200000/250= 800 units/hr)

m. L/hr to mg or units/hr n Protonix 100 mg/150 m. L is hanging, pump is set for 25 m. L/hr. How many mg/hr is patient receiving? n NS with 40 m. Eq of K+ is hanging, pump is set at 60 m. L/hr. How may m. Eq of K+ is the patient receiving each hour?

m. L/hr to mg or units/hr n Protonix 100 mg/150 m. L is hanging, pump is set for 25 m. L/hr. How many mg/hr is patient receiving? n 100 mg: 150 m. L: : X mg: 25 m. L 150 X=2500 150 n = 16. 67 mg/hr or about 17 mg/hr 1 L NS with 40 m. Eq of K+ is hanging, pump is set at 60 m. L/hr. How may m. Eq of K+ is the patient receiving each hour? 1000 m. L: 40 m. Eq: : 60 m. L: X m. Eq 1000 X = 2400 = 2. 4 m. Eq/hr 1000