Drug Delivery and IV Rates Calculations PDF

Drug Delivery and IV Rates Drug Dose Calculations Drug dosage calculations are required when the amount of medication ordered (or desired) is different from what is available on hand for the nurse to administer. When medication is given in tablets, the QUANTITY = 1 Tablet or 1 since the a...

Drug Delivery and IV Rates Drug Dose Calculations Drug dosage calculations are required when the amount of medication ordered (or desired) is different from what is available on hand for the nurse to administer. When medication is given in tablets, the QUANTITY = 1 Tablet or 1 since the amount of medication available is specified per Example 1: Toprol XL, 50 mg PO (by mouth), is ordered. Toprol XL is available as 100 mg per tablets. How many tablets would the nurse administer? Example 1: Toprol XL, 50 mg PO, is ordered. Toprol XL is available as 100 mg per tablets. How many tablets would the nurse administer? Step 1: Determine your givens. Amount desired (D) = 50 mg Amount on hand (H) = 100 mg tablets Quantity = 1Tablet Step 2: Plug in what you know into the formula and simplify. x 1Tablet = 0.5 tablets Example 2: 1200 mg of Klor-Con is ordered. This medication is only available as 600 mg per tablet. How many tablets should the nurse give?  Example 2: 1200 mg of Klor-Con is ordered. This medication is only available as 600 mg per tablet. How many tablets should the nurse give? Step 1: Determine your givens. Amount desired (D) = 1200 mg Amount on hand (H) = 600 mg Quantity = 1 tablet Step 2: Plug in what you know into the formula and simplify. x 1 tablet = 2 tablets Example 3: Dilantin-125 is available as 125 mg/5 mL. Dilantin-125, 0.3 g PO, is ordered. How much should the nurse administer to the patient? Example 3: Dilantin-125 is available as 125 mg/5 mL. Dilantin-125, 0.3 g PO, is ordered. How much should the nurse administer to the patient? Step 1: Determine your givens. Amount desired (D) = 0.3 g Amount on hand (H) = 125 mg Quantity = 5 mL Step 2: Convert 0.3 g to mg (since the ordered dose is in grams but the drug is available on hand in milligrams). 0.3 g x = 300 mg Step 3: Plug in what you know into the formula and simplify. x 5mL = 12 mL Example 4: Furosemide is available as 40 mg in 1 mL. 10 mg is ordered to be administered through an IV. What amount of furosemide should the nurse administer? Example 4: Furosemide is available as 40 mg in 1 mL. 10 mg is ordered to be administered through an IV. What amount of furosemide should the nurse administer? Step 1: Determine your givens. Amount desired (D) = 10 mg Amount on hand (H) = 40 mg Quantity = 1 mL Step 2: Plug in what you know into the formula and simplify. x 1mL = 0.25 ml Dosage Calculations based on Body Weight Dosage calculations based on body weight are required when the dosage ordered and administered is dependent on the weight of the patient. For example, many pediatric drugs are ordered and given per weight (usually in kg). Dosage calculations based on body weight are calculated in two main stages. Dosage Calculations based on Body Weight Example 1: Medrol 4 mg/kg is ordered for a child weighing 64.8 lb. Medrol is available as 500 mg/4mL. How many milliliters of medication must the nurse administer?  Step 1: Determine your givens. Weight: 64.8 lb Dosage ordered: 4mg/kg Available on hand: 500 mg/4mL Step 2: Convert 64.5 lb to kg 64.8 lb = 29.45 kg infant’s weight Step 3: Calculate the required dosage (mg) of medication based on the child’s weight. Weight (kg) x Dosage Ordered (per kg) = Y (Required dosage) 29.45 kg x = 117.8 mg required dosage of medication Step 4: Calculate the volume of medication (mL) to be administered based on what’s available on hand. x Quantity = Y x 4 mL = 0.942 mL lb→kg→mg drug→ml 64.8 lb x = 0.942 mL Example 2: A doctor prescribes 250 mg of Ceftin to be taken by a 20.5 lb infant every 8 hours. The medication label indicates that 75-150 mg/kg per day is the desired dosage range. Is this doctor's order within the desired range? Example 2: A doctor prescribes 250 mg of Ceftin to be taken by a 20.5 lb infant every 8 hours. The medication label indicates that 75-150 mg/kg per day is the desired dosage range. Is this doctor's order within the desired range? Step 1: Determine your givens. Weight: 20.5 lb Dosage ordered: 250 mg every 8 hours Desired dosage range: 75-150 mg/kg per day Step 2: Convert 20.5 lb to kg 20.5 lb = 9.32 kg  Step 3: Calculate the minimum and maximum dosage for a 9.32 kg infant. Minimum dosage: 9.32 kg x = 699 mg Maximum dosage: 9.32 kg x = 1398 mg Step 4: Calculate the amount of medication the doctor has ordered for one day or24hours. 24 hr ÷ 8 hr = 3 times per day The doctor has ordered the medication to be given 3 times per day. Every dose is 250 mg. 250 mg x 3 = 750 mg the doctor has ordered 750 mg of medication per day. Step 5: Compare the total amount of medication ordered for one day to the dosage range listed on the medication label. 750 mg is within the desired range of 699- 1398 mg since 699 < 750 < 1398 Therefore, the doctor has ordered a dosage within the desired range. Calculation of Intravenou s Drip Rates Calculation of Intravenous Drip Rates In these types of calculations, for a given volume, time period, and drop factor (gtts/mL), the required IV flow rate in drops per minute (gtts/min) is calculated. Note: Since a fraction of a drop is not possible to give to a patient, it is usual to round the answers to the nearest whole number. Example 1: Calculate the IV flow rate for 250 mL of 0.5% dextrose to be administered over 180 minutes. The infusion set has drop factor of 30 gtts/mL.  Step 1: Determine your givens. Volume: 250 mL Time: 180 min Drop Factor: 30(gtts/mL) Step 2: Use the formula to calculate the IV flow rate. No unit conversions are required. Remember to round the final answer to the nearest whole number. Drop Factor (gtts/mL) = Y (Flow Rate in gtts/min) 30(gtts/mL)=41.66 (gtts/mL) Therefore, the IV flow rate is 42 gtts/min. Example 2: The infusion set is adjusted for a drop factor of 15 gtts/mL. Calculate the IV flow rate if 1500 mL IV saline is ordered to be infused over 12 hours.  Step 1: Determine your givens. Volume: 1500 mL Time: 12 hours Drop factor: 15 gtts/mL Step 2: Convert 12 hours into minutes. 12 h x 60 min/h = 720 min Step 3: Use the formula to calculate the IV flow rate (gtts/min). 15 gtts/mL =31.25 gtts/mL Therefore, the IV flow rate is 31 gtts/min. Calculation of Flow Rate for an Infusion Pump Calculation of Flow Rate for an Infusion Pump Infusion pumps do not have a calibrated drop factor. The flow rate depends on the volume of fluid ordered and the time of infusion. Example 1: 1200 mL D5W IV is ordered to infuse in 10 hours by infusion pump. Calculate the flow rate in milliliters per hour. Example 1: 1200 mL D5W IV is ordered to infuse in 10 hours by infusion pump. Calculate the flow rate in milliliters per hour. Step 1: Determine your givens. Volume: 1200 mL Time: 10 h Step 2: Since the volume is given in mL and the time is given in hours, the flow rate can be calculated in one step using the formula. Step 3: Use the formula to calculate the flow rate (ml/h). =120 ml/h Example 2: 600 mL of antibiotic is to be infused over the 180 minutes by an infusion pump. Calculate the flow rate (mL per hour).  Step 1: Determine your givens. Volume: 600 mL Time: 180 min Step 2: Convert 180 min into hours since the flow rate must be stated in mL/h. 180 min = 3 h Step 3: Calculate the flow rate in mL/h using the formula. = 200 ml/h Preparing Dosages  Preparing Dosages Example: If a 32.4 lbs patient requires 10 mL oral suspension of an antibiotic to be taken twice daily for 10 days, and the recommended dosage is 15.0 mg/kg, then how many grams of this antibiotic needs measured out and dissolved in the 200 mL solutions?  Given: body mass: 32.4 lb Desired dosage: 15.0 mg/kg 10 ml ,twice daily, 10 days → 200 ml plan: Lb → kg (body mass)→ mg (drug) → g (drug) 32.4 lbs × × × × × 10 days = 4.418 g  Combining all of the previous formulas Example: A 175 lb patient is on an IV drip, which is set at 0.5 ml/min. The recommended dosage of the prescribed drug to be delivered is 25 mg/kg and the solution contains 150 mg/ml solution of the drug. How many minutes do you set the IV drip for? Worked- Examples 500 mg drug A is ordered for the patient. Drug A is available as 25 mg/5 mL. How much should you administer to the patient? 5 ml = 100 ml Dilantin-125 is available as 25 mg in 1 mL. The doctor order 225 mg be administered. How much should you administer? 1 ml = 9 ml Furosemide, which label indicates the dose is 2 mg/kg, is ordered for a patient weighing 100 lb. It is available as 25 mg/2 mL. How much should you administer? plan: Lb → kg (body mass)→ mg (drug) → ml (drug) 100 lbs × × × = 7.27 ml If a 40lb patient required 10 mL of Medrol 4 times a day for 3 days and the recommended dosage is 10 mg/kg. How many milligrams of Medrol must you dissolve in 120 mL? plan: Lb → kg (body mass)→ mg (drug) 40 lbs × × × 3 days =2181.8 mg = 2200 mg Aggrastat at 12.5 mg in 250 mL is prescribed to be infused at a rate of 6.0 mg/kg over 1 hr in a patient who weighs 100.0 lb. What is the flow rate in mL/hr? Given numbers: 12.5 mg in 250 mL is prescribed rate of 6.0 mg/kg over 1 hr patient who weighs 100.0 lb flow rate in mL/hr? plan: Lb → kg (body mass)→ mg (drug) → ml (drug)→ flow rate(ml/h) 100.0 lbs × × × = 5454.54 ml/h = 5500 ml/h If a 110.0 lb patient is prescribed a drug to be administered over 150 min by an IV drip. The recommended dose is 40 mg/kg and the drugs is prepared as 25 mg/ml. How many milliliters need to be administered and what would be the flow rate of the IV (mL/min)? Given numbers: 110 lb patient, 150 min , 40 mg/kg , 25 mg/ml plan: Lb → kg (body mass)→ mg (drug) → ml (drug)→ flow rate(ml/h) 110.0 lbs × × × = 80 ml flow rate of the IV (mL/min) = = 0.53 ml/min = 0.5 ml/min If a 95 lbs patient requires 20mL oral of an antibiotic to be taken twice daily for 10 days, and the recommended dosage is 25 mg/kg, then how many grams of this antibiotic needs measured out and dissolved in the 400 mL solutions. Given numbers: 95 lb patient, 25 mg/kg , 20mL twice daily for 10 days plan: Lb → kg (body mass)→ mg (drug) → g (drug) 95 lbs × × × × 10 days= 21.59 g 22 g A 125 lb patient is on an IV drip, which is set at 1.0 ml/min to be delivered over 360 min. The recommended dosage of the prescribed drug to be delivered is 60 mg/kg. What concentration of the drug should be prepared (in mg/ml)? Given numbers: 125 lb patient 60 mg / kg is prescribed rate of 1.0 ml/min over 360 min plan: Lb → kg (body mass)→ mg (drug) → mg/ml (drug) 125 lbs × × × = 9.46969696969697 mg/ml 9 mg/ml If 1.4% of the mass of a human body is calcium, how many kilograms of calcium are there in a 125-pound man? Given numbers: 1.4 kg calcium/100 kg of body mass 125 lbs body mass plan: Lb → kg (body mass)→ kg calcium 125 lbs × × = 0.795 kg calcium