Dosage Calculations Part 3
Dosage Calculations: Part 3
Introduction to Dimensional Analysis
- The session begins with a focus on dimensional analysis as a method for dosage calculations, emphasizing the importance of understanding conversion factors.
- An example is presented using amoxicillin, where the calculation involves converting dosages from milligrams to milliliters based on available stock.
Example Calculation: Amoxicillin
- The instructor discusses how to calculate the number of tablets needed for acetaminophen (Tylenol), highlighting that one gram equals one thousand milligrams.
- The calculation shows that for a desired dose of one gram, approximately three tablets are required after rounding down from 3.07 tablets.
Individualized Drug Dosages
- Transitioning to individualized drug dosages, the discussion includes calculating based on body weight and surface area.
- A specific example is given involving enoxaparin (Lovenox), where patient weight in pounds is converted to kilograms for accurate dosing.
Weight Conversion and Dosage Calculation
- The instructor explains how to convert 200 pounds into kilograms (approximately 91 kg), which is then used to determine the appropriate dosage of enoxaparin at 1 mg/kg.
- Further calculations show that this results in a total dosage of 91 mg, demonstrating practical application of the formula.
Additional Examples and Safety Checks
- Another example involves fluorouracil with a maximum daily dose limit; calculations confirm that a prescribed dose remains within safe limits.
- A final case study presents cannabisin dosing based on patient weight, reinforcing the need for careful conversions and calculations in medication administration.
Pediatric Dosage Considerations
Calculating Pediatric Dosage Based on Body Surface Area
Understanding Body Surface Area (BSA) Calculation
- The calculation begins with the height and weight of a patient, where the height is noted as 50 cm and the corresponding weight is measured in kilograms. The intersection of these values leads to a body surface area (BSA) of 0.4 m².
- The formula for calculating BSA involves using a constant value; here, it’s stated that the normal adult dose is 250 mg. This dosage will be adjusted based on the calculated BSA.
Calculating Pediatric Dosage
- To find the pediatric dosage, the formula applied is: textPediatric Dose = left( fractextBSA1.7 right) times textAdult Dose . Substituting in values gives 0.4/1.7 times 250 = 58.8. However, this value needs rounding for practical application in pediatrics.
- After recalculating, it was confirmed that 0.4/1.7 = 0.2, leading to a final pediatric dosage of approximately 50 mg after proper adjustments are made from initial calculations which were incorrect initially at higher values like 58 mg due to miscalculations during steps taken earlier in the process.
Final Confirmation of Correct Dosage