Lesson 24 — Math for Pharmacology

Half B · HLT420B·Kinn's Ch 14·NHA: Foundational Knowledge & Basic Science (10%)

Source

All procedural steps, PURPOSE rationales, and topic content below are verbatim from MedCerts HLT420B Storyline modules. Quiz items have been normalized to multiple-choice format with verbatim source rationales. Reference textbook: Niedzwiecki & Pepper, Kinn's The Clinical Medical Assistant, 15th ed., Chapter 14. No outside material added.

Learning Objectives — NHA-aligned
Module L24-01 · Procedural skill

Basic Math

Goal: To calculate the correct dose amount and choose the correct equipment to complete the provider's order.

Equipment
  • Patient's record
  • Provider's drug order
  • Premixed syringes of Bicillin, available as 0.6 million International Units/syringe in a 1-mL syringe
  • Premixed syringes of Bicillin, available as 1.2 million International Units/syringe in a 1-mL syringe
  • Pencil and paper
  1. Verify the order with the provider. Read the order in quiet surroundings to make sure you fully understand it.
  2. Examine the drug labels to see what strengths and amounts are available.
  3. The premixed Bicillin in a 1-mL syringe with a strength of 1.2 million International Units/syringe is the closest to the 1 million International Units ordered by the provider.
  4. If you chose the syringe with 0.6 million International Units, you would have to give the patient two injections—a single 0.6 million International Unit syringe plus part of another 0.6 million International Unit syringe—to administer the 1 million International Units ordered.
  5. Write down the standard formula.
    Purpose

    To eliminate the chance of error, orders should never be carried out unless the calculations have been completed in writing.

  6. Rewrite the formula, placing the known quantities into the proper place in the formula.
  7. The unknown value (x) will be the amount of the drug to give.
  8. Work the proportion problem by cross-multiplying to solve for x.
  9. To solve for x, divide each side of the equation by 1.2 million International Units.
Module L24-02 · Procedural skill

Dosage Calculations

Goal: To choose the correct system of measurement and calculate the correct dose amount per the provider's order.

Equipment
  • Patient's record
  • Provider's drug order
  • Amoxicillin solution, 50 mg per 1 mL
  • Pencil and paper
  • Standard mathematical formula
  • Conversion equivalent: 5 mL = 1 tsp
  1. Verify the order with the provider. Read the order in quiet surroundings to make sure you fully understand it.
  2. Write out the order.
  3. Examine the drug labels to see what strengths and amounts are available.
  4. Convert the ordered system of measurement to the system of measurement on the label.
  5. Place the amount ordered on the left side of the equation and the conversion factor on the right side so that similar units (in this problem, mL) can be cancelled.
  6. The label states that there are 50 mg of amoxicillin in every 1 mL of solution.
  7. To determine how many mg the child will receive in each dose, use the standard formula.
  8. Write out the formula first.
    Purpose

    To eliminate the chance of error, orders should never be carried out unless the calculations have been completed in writing.

  9. Rewrite the formula, placing the known quantities into the proper place in the formula, and using the system of measurement on the label.
  10. The unknown (x) will be the amount of the drug to give (amount to give).
  11. Work the proportion problem by cross-multiplying to solve for x. The mL units of measure will cancel each other out.
  12. The child should receive 0.8 tsp of amoxicillin, measured in a pediatric oral syringe, which contains 200 mg per dose.
Practice quiz · verbatim from MedCerts

Knowledge-check items

Click an answer to lock it in — you'll see the rationale below. Reset any time to re-attempt. Items originally formatted as true/false, fill-in-blank, or drag-and-drop have been normalized to multiple choice; the source format is noted in the eyebrow.

L24-01 · Basic Math

Q1 · L24-01 · normalized from fitb
The physician orders a 195 mg dose of Phenobarbital to be administered to a patient. The strength of the Phenobarbital available is 64.8 mg/tablet. How many tablets should be given to the patient?
Rationale
"To eliminate the chance of error, orders should never be carried out unless the calculations have been completed in writing."

Using the standard proportion formula (dose ordered ÷ strength available × quantity = amount to give), 195 mg ÷ 64.8 mg × 1 tablet = 3 tablets. This calculation applies the mathematical formula taught in the lesson to determine the correct tablet quantity.

Source: L24-01 Knowledge Check

L24-02 · Dosage Calculations

Q1 · L24-02 · normalized from fitb
The physician orders an injection of 200 mg of Clindamycin to be administered to a patient. The strength of the injectable Clindamycin available is 300 mg/6 mL. How many mL should be given to the patient by injection?
Rationale
"To eliminate the chance of error, orders should never be carried out unless the calculations have been completed in writing."

Using the standard proportion formula with the available strength, 200 mg ÷ 300 mg × 6 mL = 4 mL. This calculation applies the mathematical formula and unit conversion principles taught in the lesson to determine the correct injection volume.

Source: L24-02 Knowledge Check