Problem 72 - Calculate With Confidence

Question

Determine the dosage in the following problems. Round dosages to the nearest tenth as indicated. The recommended dose for acyclovir is \(250 \mathrm{mg}\) per \(\mathrm{m}^{2}\). The child has a BSA of \(0.82 \mathrm{~m}^{2}\)

Step-by-Step Solution

Answer

The dosage is 205.0 mg.

Step 1: Understand the Problem

The problem asks us to calculate the dosage of acyclovir for a child with a given body surface area (BSA). We know the recommended dose per square meter and need to apply this to the actual BSA provided.

Step 2: Set Up the Calculation

To determine the total dosage needed, multiply the recommended dosage per square meter by the child's BSA. The formula is: \[ \text{Total Dosage} = \text{Dose per } \mathrm{m}^2 \times \text{BSA} \] In this case, that means \[ 250 \mathrm{~mg/m}^2 \times 0.82 \mathrm{~m}^2 \].

Step 3: Perform the Multiplication

Carry out the multiplication of the two numbers: \[ 250 \times 0.82 = 205 \] This means the calculated dosage is 205 mg.

Step 4: Round the Dosage

The problem asks us to round the calculated dosage to the nearest tenth. In this case, 205 is already a whole number, so expressed as 205.0 when rounded to the nearest tenth.

Key Concepts

Acyclovir Dosage

Acyclovir is a medication used to treat viral infections such as herpes simplex virus infections. When it comes to prescribing this medication,
it's important for healthcare providers to calculate the correct dosage to ensure it's effective and safe. The recommended dose for acyclovir is often given in terms of milligrams per square meter of body surface area (\( ext{mg/m}^2 \)).To determine the appropriate acyclovir dosage for a patient, you need two key pieces of information:

• The recommended dose per square meter, which in this case is \( 250 \text{ mg/m}^2 \).
• The patient's body surface area (BSA), which might vary from child to adult.

By multiplying these two factors, you find the total milligrams of acyclovir needed. For example, a child with a BSA of 0.82 \( ext{m}^2 \) would need a total dosage of \( 250 \times 0.82 = 205 \text{ mg} \). Rounding to the nearest tenth, as often required, doesn't change this total since 205 is already a whole number.

Body Surface Area

Body surface area (BSA) is a measure used in medicine to help calculate dosages of medications, such as acyclovir, especially in pediatric patients. BSA is considered a better measure of metabolic mass than body weight alone because it accounts for the distribution of tissues.The most common way to calculate BSA is by using a formula like the Du Bois or Mosteller formula:

• Du Bois Formula: \[ ext{BSA} = 0.007184 imes ext{Height}^{0.725} imes ext{Weight}^{0.425} \]
• Mosteller Formula: \[ ext{BSA} = rac{ ext{Height} ( ext{cm}) imes ext{Weight} ( ext{kg})}{3600} \]

This measure is used to adjust medication dosages to ensure they're appropriate for the patient's level of body tissue, providing safer and more effective treatment by reducing the risk of overdose.
Accurate calculation of BSA is crucial, as miscalculation can lead to incorrect dosing, potentially causing either under-treatment or adverse effects.

Pharmaceutical Calculations

Pharmaceutical calculations are essential skills for healthcare professionals, ensuring patients receive the correct drug dosages. These calculations often include determining dosages based on a patient's body measurements, like weight or body surface area (BSA).When you calculate a pharmaceutical dosage, follow these general steps:

• Identify the dosage requirements per unit (such as \( ext{mg/m}^2 \) in the case of acyclovir).
• Obtain the patient's body measurements, such as BSA or weight.
• Use the formula to calculate the total dosage necessary.
• Finally, round the result to the nearest appropriate unit.

In the example of acyclovir dosage, the calculation involves multiplying the given dosage (\( 250 \text{ mg/m}^2 \)) by the child's BSA (0.82 \( ext{m}^2 \)), giving a total dosage of 205 mg. Always verify results and round-off calculations to ensure clarity and precision when administering medications, as this can significantly affect treatment outcomes.