PHAR W2

MEDICATIONS and CALCULATIONS

• The systems of measurement are very important.
• When calculating drugs, it is very important that we know conversion and the calculation of weight, volume, and height
• You have to know the different abbreviations for these measurements
  • Universally-accepted only
  • Most are small letters

SYSTEMS OF MEASUREMENT

• METRIC SYSTEM

  • Internationally-recognized system of measurement known as the international system of units
  • Decimal system based on the power of ten
  • Most manufacturers of drugs use this system

• APOTHECARY SYSTEM

  • Historically-used
  • Before it is used in medical recipes by physicians and scientists
  • Occasionally, V = oz and W = g are used

• HOUSEHOLD SYSTEM

  • What we see as being used in the kitchen
  • Not as accurate as metric system due to lack of standardization of utensils

METRIC SYSTEM

• WEIGHT

  • gram (g, G) > 1000g = 1kg
  • kilogram (kg, Kg)
  • milligram (mg) > 1000mg = 1g
  • microgram (mcg) > 1000mg = 1mg
  • nanogram (ng) > 1,000,000 ng = 1 mg

• VOLUME

  • liter (l, L)
  • milliliter (ml, mL) > 1000ml = 1L

• HEIGHT

  • meter (m, M)
  • centimeter (cm) > 100cm = 1m
  • millimeter (mm) > 1,000mm = 1m

• Mass, length, distance, area, speed, time

APOTHECARY SYSTEM

• WEIGHT

  • grain (gr) > 1gr = 60mg
  • pound (lb) > 1kg = 2.2 lb

• VOLUME

  • ounce (oz) > 1oz = 30ml
  • dram (dr) > 8 dr = 1oz
  • minim (min) > 1min = 1 drop
  • quart (qt) > 1 qt = 1000 ml
  • pint (pt) > 1pt = 500 ml

• HEIGHT

  • inches (in) > 1 inch = 2.54 cm

HOUSEHOLD SYSTEM

• WEIGHT

  • pound (lb)

• VOLUME

  • teaspoon (t, tsp) > 1tsp = 5ml
  • tablespoon (T, tbsp) > 1tbsp = 15ml
  • cup (c, C) > 1 cup = 180 ml
  • glass > 1 glass = 240 ml
  • drop (gt, gtt, gtts) > 15 drops = 1ml

• HEIGHT

• Inches (in)

BASIC FORMULA

To be able to compute how much you are going to give to a patient, memorize this formula.

• D

  • Desired dose
  • Dose that are needed to be given to a patient
  • Doses are actually weight (g, kg, mg)

  \

• H

  • Stock dose, dose on hand
  • Commercially-available dose available made from the pharmaceutic company

• Q or V

  • Quantity, volume, drug form
  • mL, cc (liquids)
  • Tablet or capsule (solids)

• X or A

  • Amount to be given

  • Also in quantity

  • Oral drugs – capsule or tablet

  • Liquid drug – mL, cc

  • Especially for the syringes:

    \

STANDARD/UNIVERSAL RULE:

• For every 100mg of powder drug, you incorporate 1 ml of sterile water.
  • Not every drug follows this rule because sometimes there are drugs that are too painful to inject.
  • Mas advantage if i-dilute para medyo mas maging malabnaw

• • X or A o Amount to be given o Also in quantity o Oral drugs – capsule or tablet o Liquid drug – mL, cc ▪ Especially for the syringes 𝐷 𝐻 × 𝑄 = 𝑋 BASIC FORMULA: EXAMPLES ORAL DRUGS, CAPSULES QUESTION Give 0.5 of cefaclor (antibiotic) PO BID GIVEN: D = 0.5g H = 250mg Q = 1 cap REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 SOLUTION: 0.5𝑔 250𝑚𝑔 × 1 𝑐𝑎𝑝 = 𝑋 • Convert the bigger unit (g) into the smaller unit (mg). 500𝑚𝑔 250𝑚𝑔 × 1 𝑐𝑎𝑝 = 𝑋 ANSWER: X = 2 CAPS ORAL DRUGS, TABLETS QUESTION Give Aspirin (NSAID) 650 mg PO Q4 PRN. • Aspirin o NSAID (non-steroidal antiinflammatory drug) o For fever and pain o Among adults, can be used as antiplatelet drug as thinner GIVEN: D = 650mg H = 325mg Q = 1 tablet REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 SOLUTION: 650𝑚𝑔 325𝑚𝑔 × 1 𝑡𝑎𝑏𝑙𝑒𝑡 = 𝑋 ANSWER: X = 2 TABLETS MYOS | 2B-BSN ORAL DRUGS, LIQUIDS Physician orders 1500 mg of liquid ibuprofen (NSAID; for fever and pain) for a child. Preparation is 100 mg per 5 ml, how many will you administer? GIVEN: D = 1500mg H = 100mg Q = 5ml REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 SOLUTION: 1500𝑚𝑔 100𝑚𝑔 × 5𝑚𝑙 = 𝑋 ANSWER: X = 75ml (Too big for a child but it’s only an example) PARENTERAL DRUGS, LIQUID FORM: Order is Furosemide (diuretic) 10 mg IV Q12. The solution is available in a 4 ml bottle. GIVEN: D = 10mg H = 10mg Q = 1ml REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 SOLUTION: 10𝑚𝑔 10𝑚𝑔 × 1 𝑚𝑙 = 𝑋 ANSWER: X = 1ml PARENTERAL DRUGS, POWDER FORM: Amoxicillin should be given 0.5 g IM Q8. The nurse incorporated 5 ml of sterile water in a 500 mg powder of drug in a vial. o If you are the nurse incorporating the water in the drug, you should note the bottle; some of the content can be used by other patients, shift, or dose; if the next nurse gets the vial, how would she know the times cue? Note the amount of diluent added as a previous nurse GIVEN: D = 0.5g H = 500mg Q = 5ml (what has been added) REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 MYOS | 2B-BSN SOLUTION: 0.5𝑔 500𝑚𝑔 × 5 𝑚𝑙 = 𝑋 ANSWER: X = 5ml • STANDARD RULE: Per 100mg drug, 1mL of sterile water is incorporated BASIC FORMULA (CONT.) • To Consider Body Weight o There are medications that are given by the doctor depending on the weight of the client, particularly children o We have to remember that the dosage (mg) you want per day (F/day) is divided into the weight of the patient (kg) 𝑚𝑔 × 𝑘𝑔 𝐹 ∕ 𝑑𝑎𝑦 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒) CONSIDERING BODY WEIGHT: EXAMPLES QUESTION 1 You are to give fluorouracil 12 mg/kg/day IV not to exceed 800 mg/day. Client weighs 132 lbs. Give the drug BID. How much dosage will be prepared per administration of drug? GIVEN: mg = 12 mg kg = 60kg (132lbs.) F/day = 2 REQUIRED: D EQUATION: 𝑚𝑔 × 𝑘𝑔 𝐹 ∕ 𝑑𝑎𝑦 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒) SOLUTION: 12𝑚𝑔 × 60𝑘𝑔 2 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒 ) ANSWER: D = 360mg CHECKING: “Not to exceed 800mg/day” GIVEN: D = 360MG F/day = 2 SOLUTION: 360mg x 2 (f/day) ANSWER: 720mg/day Therefore, the medication is accurate because it is lesser than 800mg/day. QUESTION 2 A ten-year-old child is prescribed 125 mg of a drug four times daily. The child weighs 88 pounds. How many milligrams per kilogram per day will be ordered for this child? GIVEN: mg = 125mg kg = 40kg (88lbs.) F/day = 4 REQUIRED: mg/kg/day EQUATION: MYOS | 2B-BSN 𝑌 𝑚𝑔 × 𝑛 (𝑔𝑖𝑣𝑒𝑛) 𝑘𝑔 𝑓/𝑑𝑎𝑦 = 𝐷 SOLUTION: 𝑌 𝑚𝑔 × 40𝑘𝑔 4 = 125𝑚𝑔 𝑌 𝑚𝑔 × 40𝑘𝑔 4

125𝑚𝑔 1 Cross multiply. 40𝑦 = 500 Cancel out by dividing by 40 on both sides. 40𝑦 = 500 40 ANSWER: Y = 12.5mg/kg/day QUESTION 3 Lanoxin 0.15 mg po Q 12h is ordered as a maintenance dose for a 9-year-old child who weighs 70 lbs. The recommended maintenance pediatric dosage of Lanoxin tablets is 7 to 10 mcg/kg/day divided and given in 2 equal doses per day. What is the minimum daily dosage for this child? GIVEN: mg = 0.15 mg kg = 31.8kg (70lbs.) REQUIRED: mcg/kg/day or minimum daily dosage EQUATION: • Recommended maintenance pediatric dosage is 7-10 mcg/kg/day given in 2 equal doses o Minimum = 7 mcg/kg/day o Maximum = 10 mcg/kg/day 𝑀𝑖𝑛. 𝑚𝑐𝑔 × 𝑛 (𝑔𝑖𝑣𝑒𝑛)𝑘𝑔 𝑑𝑎𝑦 SOLUTION: 7𝑚𝑐𝑔 × 31.8𝑘𝑔 1 𝑑𝑎𝑦 = 222.6 𝑚𝑐𝑔/𝑑𝑎𝑦 Convert 222.6mcg to mg. 222.6 𝑚𝑐𝑔 × 1𝑚𝑔 1000𝑚𝑐𝑔 ANSWER: 0.22 mg/day CHECKING: GIVEN: D = 0.15mg F/DAY = 2 SOLUTION: 0.15mg * 2 ANSWER: 0.30 mg/day It is correct because it is smaller than the minimum daily dosage needed for the child. BODY SURFACE AREA • Body surface area (BSA) unit is in m2. Same formula when considering body weight, but change kg to m2 instead. 𝑚𝑔 × 𝑚2 𝐹 ∕ 𝑑𝑎𝑦 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒) MYOS | 2B-BSN BODY SURFACE AREA: EXAMPLES QUESTION 1 Order is mephenytoin 200 mg/m2/day PO in 3 divided doses. The drug comes in a 10 ml solution bottle of 20 mg/2 ml. If child is 47 inches tall and weighs 40.5 kg, what is the amount to give per administration? GIVEN: Height: 47 inches Weight: 40.5kg mg = 200mg/m2/day f/day = 3 REQUIRED: Amount to give per administration EQUATION: 𝑚𝑔 × 𝑚2 𝐹 ∕ 𝑑𝑎𝑦 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒) To get BSA in m2, determine height and weight first. Then get BSA in m2 using a nomogram. SOLUTION: 200𝑚𝑔 × 1.2 𝑚2 3 = 𝐷( 𝑚𝑔 𝑑𝑜𝑠𝑒) ANSWER: D = 80mg (DESIRED DOSE) Finding the amount to give per administration… GIVEN: D = 80mg H = 20mg Q = 2ml REQUIRED: X EQUATION: 𝐷 𝐻 × 𝑄 = 𝑋 SOLUTION: 80𝑚𝑔 20𝑚𝑔 × 2𝑚𝑙 = 𝑋 ANSWER: X = 8ml VIALS AND AMPULES, SYRINGES, INTRAVENOUS DRUGS, AND FLUIDS • Glass vials • Plastic vials • Ampules VIALS AND AMPULES MYOS | 2B-BSN VIALS AND AMPULES: EXAMPLE QUESTION 1 Ampicillin vial contains 500 mg of powder solution. The nurse incorporates 5 ml of sterile water. The client should receive 125 mg of the drug through IV q8h for 7 days. How many Ampicillin vials will the client consume to finish the drug regimen? Computation for the Number of Doses per Vial GIVEN: H = 500mg D = 125mg REQUIRED: No. of vials EQUATION: 𝐻 𝐷 = 𝐷𝑜𝑠𝑒𝑠/𝑣𝑖𝑎𝑙 SOLUTION: 500𝑚𝑔 125𝑚𝑔 ANSWER: 4 DOSES/VIAL In 7 days, how many vials will the patient use? GIVEN: Q8H = 3 doses a day Entire regimen = 7 days REQUIRED: How many vials in 7 days? EQUATION/SOLUTION: 3 𝑑𝑜𝑠𝑒𝑠 𝑑𝑎𝑦 ∗ 7 𝑑𝑎𝑦𝑠 = 21 𝑑𝑜𝑠𝑒𝑠 21 𝑑𝑜𝑠𝑒𝑠 4 𝑑𝑜𝑠𝑒𝑠 𝑣𝑖𝑎𝑙 = 5.25 𝑣𝑖𝑎𝑙𝑠 ANSWER: 6 VIALS (ROUND UP) SYRINGES o The higher the gauge, the smaller the needle • Prefilled Syringe MYOS | 2B-BSN INTRAVENOUS DRUG AND FLUIDS • IVF Rate (gtts/min) 𝑚𝑙 ℎ𝑟 𝑥 𝐷𝐹 ( 𝑔𝑡𝑡𝑠 𝑚𝑙 ) 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 o Manual regulation • Drop Factor (gtts/ml) o Macroset ▪ 15 gtts/ml or depends on manufacturer ▪ Big drop from the plastic o Microset ▪ 60 gtts/ml ▪ Small drop from the needle • Calibrated Cylinders o Also called soluset o Intended for children o Sterile o Are microsets (60gtts/ml) • Infusion (top) pump, syringe pump (below) o When you have the machine, you don’t need the formula. o Can input ml/hr • Secondary or intermittent line MYOS | 2B-BSN INTRAVENOUS DRUGS AND FLUIDS: EXAMPLES QUESTION 1: MACROSET The nurse must give D5LR 1 L for 8 hours using a macroset of 15 gtts/ml. At what rate will the nurse regulate the IVF? GIVEN: ml = 1L = 1000ml hr = 8 hours DF = 15 gtts/ml REQUIRED: Gtts/min EQUATION: 𝑚𝑙 ℎ𝑟 𝑥 𝐷𝐹 ( 𝑔𝑡𝑡𝑠 𝑚𝑙 ) 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 SOLUTION: 1000𝑚𝑙 8ℎ𝑟 𝑥 15𝑔𝑡𝑡𝑠/𝑚𝑙 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 ANSWER: 31.25 gtts/min = 32 gtts/min (ROUND UP) QUESTION 2: MICROSET The doctor orders 500 ml of D5IMB to be given for 12 hours using a soluset. The nurse must set the IV fluid at what rate? GIVEN: ml = 500ml hr = 12 hours DF = 60 gtts/ml REQUIRED: Gtts/min EQUATION: 𝑚𝑙 ℎ𝑟 𝑥 𝐷𝐹 ( 𝑔𝑡𝑡𝑠 𝑚𝑙 ) 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 SOLUTION: 500𝑚𝑙 12ℎ𝑟 𝑥 60𝑔𝑡𝑡𝑠/𝑚𝑙 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 ANSWER: 41.67 gtts/min = 42 gtts/min (ROUND UP) QUESTION 3 At what rate will the nurse regulate a client’s IV fluid if the doctor orders a bolus of 600 ml of D5LR to run for 3 hours. The administration set delivers 25 gtts/ml. GIVEN: ml = 600 hr = 3 hours DF = 25 gtts/ml REQUIRED: Gtts/min EQUATION: 𝑚𝑙 ℎ𝑟 𝑥 𝐷𝐹 ( 𝑔𝑡𝑡𝑠 𝑚𝑙 ) 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 SOLUTION: 600𝑚𝑙 3ℎ𝑟 𝑥 25𝑔𝑡𝑡𝑠/𝑚𝑙 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 ANSWER: 83.33 gtts/min = 84 gtts/min (ROUND UP) QUESTION 4 A client’s 500 ml bottle of IV runs at 50 gtts/min in a microset. How long will this fluid be consumed? GIVEN: ml = 500ml gtts/min = 50 gtts/min REQUIRED: How long will this fluid be consumed? (hr) EQUATION: 𝑚𝑙 𝑦 ℎ𝑟 𝑥 𝐷𝐹 ( 𝑔𝑡𝑡𝑠 𝑚𝑙 ) 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 SOLUTION: 500𝑚𝑙 𝑦 ℎ𝑟 𝑥 60 𝑔𝑔𝑡𝑠 𝑚𝑙 60 𝑚𝑖𝑛𝑢𝑡𝑒𝑠 = 50 𝑔𝑡𝑡𝑠/𝑚𝑖𝑛 Cross multiply. 500 = 60 60𝑦 = 50 500 = 50 50 MYOS | 2B-BSN ANSWER: y = 10 hours QUESTION 5 The 6 am nurse upon arrival checks a client’s 1 L of IVF bottle and reads its level at 400 cc at 25 gtts/min. The order is for the bottle to be consumed for 10 hours using a macroset of 15 gtts/ml. Given the level at 6 am, what time should the remaining fluid be consumed? GIVEN: ml = 1L = 1000ml Current level = 400 cc = 400ml Gtts/min = 25 gtts/min Hr = 10hrs REQUIRED: Time before consumption of the remaining fluid (400ml) EQUATION: 𝑚𝑙 ℎ𝑟 SOLUTION: 1000𝑚𝑙 10ℎ𝑟 ANSWER: 100ml/hr CHECKING: 𝟒𝟎𝟎𝒎𝒍 𝟏𝟎𝟎𝒎𝒍/𝒉𝒓 = 𝟒 𝒉𝒓𝒔 4 hrs + 6am (the time the nurse checked the level) = 10AM ANSWER: 10AM QUESTION 6 The nurse regulates Lactated Ringer’s 1,500 ml IV for 12 hours at 125 ml/hr. Drop factor is 20 gtts/min. After 6 hrs, how much solution is still remaining in the bottle? GIVEN: ml/hr = 125ml/hr hr = 6 hours REQUIRED: Remaining solution after n hours EQUATION: 𝑚𝑙 ℎ𝑟 𝑥 ℎ𝑜𝑢𝑟𝑠 SOLUTION: 125𝑚𝑙 1ℎ𝑟 × 6 ℎ𝑜𝑢𝑟𝑠 = 750 𝑚𝑙 1500 ml (full amount of IV) – 750 ml (after 6 hours) = 750 ml (after another 6 hours) ANSWER: 750ml QUESTION 7 The nurse must give a 40 ml of metronidazole antibiotic for 30 minutes to a client. Using an infusion pump, at what rate will the nurse set the machine? GIVEN: ml = 40ml hr = 30 mins = 0.5 hr REQUIRED: Rate in infusion pump EQUATION: 𝑚𝑙 ℎ𝑟 SOLUTION: 40𝑚𝑙 0.5ℎ𝑟 ANSWER: 80ml/hr QUESTION 8 A child with AB+ blood needs a transfusion of PRBC 50 cc to run for 4 hours. The nurse, using a syringe pump, will set the machine at what rate? GIVEN: ml = 50cc = 50ml hr = 4 hours REQUIRED: Rate in syringe pump EQUATION: 𝑚𝑙 ℎ𝑟 SOLUTION: 50𝑚𝑙 4ℎ𝑟 ANSWER: 12.5ml/hr MYOS | 2B-BSN FLUID INTAKE: EXAMPLES A client drank 4 oz of juice and 1 pt of ice cream for an 8-hour shift. The nurse also noted an IVF of D5LR 1 L for the whole shift and amikacin drip of 20 cc for 30 minutes. • What is the total oral intake? 4 oz of juice + 1 pt. of ice cream = 30ml of juice + 500ml of ice cream = 620ml • What is the total IVF intake? 1L + 20cc = 1000ml + 20ml = 1020ml • What is the total fluid intake? 620ml + 1020ml = 1640ml METRIC UNITS OF MEASUREMENT UNIT NAMES AND ABBREVIATIONS MEASUREMENTS Gram (weight) 1 kilogram (kg, Kg) 1000 g 1 gram (g, gm, G, Gm) 1 g 1 milligram (mg) 0.001 g 1 microgram (mcg) 0.000001 g 1 nanogram (ng) 0.000000001 g Liter (volume) 1 kiloliter (kl, KL) 1000 L (l) 1 liter (L, l) 1 L (l) 1 milliliter (mL) 0.001 L (l) Meter (length) 1 kilometer (km) 1000 m 1 meter (m, M) 1 m 1 centimeter (cm) 0.01 m 1 millimeter (mm) 0.001 m NOTE: 1 mL (milliliter) = 1 cc (cubic centimeter). Values are the same in drug and fluid therapy. 1 mg (milligram) = 1000 mcg (micrograms). HOUSEHOLD EQUIVALENTS IN FLUID VOLUME 1 MEASURING CUP 8 OUNCES (oz) 1 medium-size glass (tumbler size) 8 ounces (oz) 1 coffee cup (c) 6 ounces (oz) (varies with cup size) 1 ounce (oz) 2 tablespoons (T) 1 tablespoon (T) 3 teaspoons (t) 1 teaspoon (t) 60 drops (gtt)* 1 drop (gt) 1 minim (min, or m) APPROXIMATE METRIC, APOTHECARY, AND HOUSEHOLD EQUIVALENTS METRIC SYSTEM APOTHECARY SYS-TEM HOUSEHOLD SYSTEM Weight 1 kg 1000 g 2.2 lb 2.2 lb *1 g 1000 mg 15 (16) gr 0.5 g 500 mg 7 1/2 gr 0.3 g 300 (325) mg 5 gr 0.1 g 100 mg 1 1/2 gr *0.06 g 60 (65) mg 1 gr 0.03 g 30 (32) mg ½ gr 0.01 g 10 mg 1/6 gr 0.6 mg 1/100 gr 0.4 mg 1/150 gr 0.3 mg 1/200 gr Volume 1 L; 1000 mL 1 qt; 32 oz (fl oz) 0.5 L; 500 mL 1 pt; 16 oz (fl oz) 0.24 L; 240 mL 8 fl oz 1 glass 0.18 L; 180 mL 6 fl oz 1 c *30 mL 1 fl oz; 8 fl dr 2 T; 6 t 15 mL ½ fl oz; 4 fldr 1 T; 3 t †5 mL 1 t 4 mL 1 fl oz; 60 ♏︎ 1 t 1 mL 15 (16) ♏︎ 15-16 gtt Height/distance 2.54 cm 1 in 1 in 25.4 mm 1 in 1 in MYO