Dosage calulations part 1

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Dosage calulations part 1

  1. 1. 1Dosage CalculationsPart 1• TODAY WE WILL PROCEED WITHDOSAGE CALCULATIONS.• THIS PART IS THE REAL NURSINGSTUFF!!!!
  2. 2. Dosage Variations• Reconstitution of powered drugs; single andmulti-strength• Pediatric meds• BSA• IV formulas• Heparin• Critical care medications2
  3. 3. Reconstitution of Powered Medications• Solute• Solvent• Directions1. Read labelinstructions2. Add diluent3. Label and calculatedose to administer3
  4. 4. 4Reconstitution of Powdered DrugsExample: Bottle of Oxacillin 2 g powderDirections on label: add 11.5ccsterile H20 for injectionEach 1.5 cc = 250 mgDose ordered is 500mg IMHow many________ cc’s will we give?250 mg: 1.5cc :: 500 mg : Xcc250X = 500mg x 1.5250X= 750X = 3cc
  5. 5. Reconstituting Medications• For Calculating Purposes:• DO NOT USE the added diluent for calculating yourdose. (see previous example)• INSTEAD USE THE RESULTINGCONCENTRATION, e.g. in the previous example itsaid the resulting concentration will be, 250mg =1.5 ml5
  6. 6. 6Single Dose ReconstitutionExample 2Order reads• Give 750mg of Ampicillin q4h IV.On hand• Ampicillin 1 g vial in powered form.• Reconstitution directions say:add 2ml sterile water for injection. Each ml contains500mg Ampicillin.How many ml would you give each dose
  7. 7. 7Reconstitution cont.• Don’t worry about the addedamount, just use resulting concentration( 500mg/ml)• 500 mg : 1ml :: 750 mg : x ml500x = 750x = 1.5 mlSo we would give 1.5ml for ordered dose.
  8. 8. 8Multiple Strength SolutionsOrder readsPenicillin G 2,250,000 units IM now.ON HandPenicillin 20 million unit vialReconstitution reads:• Add 11.5cc for 1,000,000 units/ml, 33cc for 500,000units/ml, and 75cc for 250,000 units/ml• Using the appropriate concentration, how many cc’sshould be given for this dose
  9. 9. Label Example9
  10. 10. 10Multiple Strength cont.• Choose 1,000,000 units/ml• since it is the closest. SO,1,000,000units :1cc :: 2,250,000units : x cc1,000,000 x = 2,250,000x = 2.25cc• So give 2.25 cc to administer dose.• Ok for IMInjection ?
  11. 11. 11MEDICAL QUESTION OF THE DAY• QUESTION:• WHAT IS AN ELIXIR
  12. 12. 12MEDICAL HUMOR• ANSWER:: WHAT A DOG DOES TOHIS MASTER.• LOL 
  13. 13. 13DOSAGE CALCUATIONBY WEIGHTORDER:Vancomycin IV 5 mg/kgPatient weights 209 lbs209 ÷ 2.2 = 95 kg95 kg X 5 mg = 475 mg
  14. 14. 14Pediatric Medications
  15. 15. 15Dosage Calculation3 Steps1. Convert lbs. – kgs. divide by 2.22. Calculate daily dosage3. Compare to recommended safe dose.
  16. 16. 16Order: Amoxicillin 125 mgP.O. q.8***Patient weight 22 lbsIS THIS DOSE SAFE?STEPS:1. 22 ÷ 2.2 = 10 kg2. 125mg q 8hr. = 125 mg x 324 hrs ÷q 8 hrs. = 3 x /day= 375 mg per day
  17. 17. 17
  18. 18. 18Pediatric Dosage3. Recommended safe dose of Amoxicillin is20-40 mg/kg/day.20mg x 10kg = 200mg /day40 mg x 10 kg = 400mg /daySo daily safe range is200mg – 400mg /dayPatient’s daily dose is 375 mg/daySo patient’s daily dose falls within SAFE range
  19. 19. Pediatric DosageExample 2• Order reads: Oxycodone 3mg p.o. now• Patient weighs 30 lbs.• Recommended safe dose of Oxycodone is0.15 mg/kg/doseIs this dose safe?19
  20. 20. 20Example 2Pediatric dosage1. 30 lbs / 2.2 = 13.64 kg.2. Ordered dose is 3 mg.3. Recommended dose is 0.15 mg/kg/dose0.15 x 13.64 = 2 mg is the maximum safedoseThis dose is not safe!
  21. 21. Example 3• Order reads: Gentamycin 5mg/kg/day divided in2 doses.• The infant weighs• 22lbs.• On hand is: Gentamycin 80mg/2ml• How many cc’s should the infant receive perdose?21
  22. 22. Example 3 (cont.)• Infant weight in kg = 22/2.2 or 10 kg• 5mg x 10mg = 50 mg /day in 2 divided doses =25 mg per dose• On hand we have Gentamycin80mg/2mlSO, 80mg : 2ml :: 25 mg: xml80x = 50x = 0.625ml per dose22
  23. 23. 23DOSAGE SAFETY• A TRAGIC MEDICATIONERROR LED TO DEATH OF 9- MONTH OLD INFANT.THE DR. ORDERED .5mg IV MSO4THE person who transcribed med DID NOT SEE THE DECIMAL MADE ITA (5 mg)DOSE ON MAR. (Medicine administration record)BABY received 2 (5mg) DOSESTWO HOURS APART.THIS IS 10 TIMES THE NORMAL DOSE TWICE!! BABY DIED!!New System POE many safety features !! Electronic recordsimproving safety
  24. 24. 24BSA(Body Surface Area)Noted as M2
  25. 25. 25Example** If you are given a recommended pediatric doseand BSA, use this formula**Drug A : 15 mg/M2(Recommended Pediatric Dose)Pts. BSA = 0.48 M2Just multiplyDosage: 15 x 0.48(BSA) =7.2 mg
  26. 26. 26Recommended AdultDose OnlyFormula on sheetIF NO RECOMMENDED CHILD DOSEIS AVAILABLE USEChild’s BSA X (times)1.7 M² adult dose(average adult BSA)WILL GIVE YOU CHILD’S DOSE
  27. 27. 27Example with no recommendedpediatric dose givenDRUG C = 25 mg( RECOMMENDED ADULTDOSE OF DRUG)CHILD’S BSA = 0.47 M ²0.47 M ² X 25 mg = 7 mg1.7 M ² CHILD’SDOSE
  28. 28. 28Example #2• Child BSA = 0.6m²• Recommended Adult dose of• Keflex = 500 mg• Find the child dose
  29. 29. 29ANSWER BSA0.6 X 500 =1.7176.47 MG = CHILDDOSE
  30. 30. 30NON-METRICBSA =wt (lbs) x ht (in)3131METRICBSA =WT (kg) x ht (cm)3600**May use to calculate adult orpediatric dose
  31. 31. 31AVERAGE 4YR OLD17KG and 103 CM360010317x3600175149..486. or.697m2or 0.7m2===
  32. 32. 32BSA• Example 2• Calculate the BSA for adult whoweighs 200lbs and is 59”tall
  33. 33. 33ANSWERUse non metric formulaBSA =200x593131= 3.768Answer = 1.94 is the BSA
  34. 34. 34MEDICAL HUMOR• QUESTION• WHAT IS A MICROGRAM
  35. 35. 35MEDICAL HUMOR• ANSWER :• A SMALL CRACKER• LOL again 

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