Dosage Calculations Book

Medication Dosage Calculator (Weight-Based)

This calculator helps determine the precise volume of liquid medication to administer based on a patient's weight and the medication's concentration. Accurate dosage calculation is critical in healthcare to ensure patient safety and therapeutic effectiveness, especially in pediatrics.

function calculateDosage() { var prescribedDosePerKg = parseFloat(document.getElementById('prescribedDosePerKg').value); var patientWeightKg = parseFloat(document.getElementById('patientWeightKg').value); var medAvailableMg = parseFloat(document.getElementById('medAvailableMg').value); var medVolumeMl = parseFloat(document.getElementById('medVolumeMl').value); var resultDiv = document.getElementById('dosageResult'); // Input validation if (isNaN(prescribedDosePerKg) || isNaN(patientWeightKg) || isNaN(medAvailableMg) || isNaN(medVolumeMl) || prescribedDosePerKg <= 0 || patientWeightKg <= 0 || medAvailableMg <= 0 || medVolumeMl <= 0) { resultDiv.innerHTML = 'Please enter valid positive numbers for all fields.'; return; } // Step 1: Calculate the total dose needed for the patient in mg var totalDoseNeededMg = prescribedDosePerKg * patientWeightKg; // Step 2: Calculate the concentration of the available medication in mg/mL var concentrationMgPerMl = medAvailableMg / medVolumeMl; // Step 3: Calculate the volume to administer in mL var volumeToAdministerMl = totalDoseNeededMg / concentrationMgPerMl; resultDiv.innerHTML = 'Volume to Administer: ' + volumeToAdministerMl.toFixed(2) + ' mL' + '(Total Dose Needed: ' + totalDoseNeededMg.toFixed(2) + ' mg, Available Concentration: ' + concentrationMgPerMl.toFixed(2) + ' mg/mL)'; }

Understanding Dosage Calculations

Dosage calculations are fundamental skills for healthcare professionals, including nurses, pharmacists, and doctors. They involve using mathematical formulas to determine the correct amount of medication to give a patient. Errors in these calculations can lead to serious adverse effects, making accuracy paramount.

Key Components of Dosage Calculation:

• Prescribed Dose: This is the amount of medication ordered by the physician, often expressed as a quantity per unit of body weight (e.g., mg/kg) or per unit of time (e.g., mg/day).
• Patient Weight: For many medications, especially in pediatric or critical care, the dose is individualized based on the patient's weight in kilograms (kg).
• Medication Concentration (Available Dose & Volume): This refers to how much medication is present in a given volume or form. For liquid medications, it's typically expressed as mg per mL (e.g., 250 mg / 5 mL).
• Desired Unit: The final form in which the medication needs to be administered (e.g., mL, tablets, capsules).

The Formula Used:

The calculator uses a two-step process for weight-based liquid medication:

1. Calculate Total Dose Needed:
   Total Dose (mg) = Prescribed Dose (mg/kg) × Patient Weight (kg)
2. Calculate Volume to Administer:
   Volume (mL) = Total Dose (mg) ÷ (Medication Available (mg) ÷ Medication Volume (mL))

Example Scenario:

A physician orders Amoxicillin 15 mg/kg for a child weighing 20 kg. The pharmacy supplies Amoxicillin suspension labeled 250 mg / 5 mL. How many mL should be administered per dose?

• Prescribed Dose (mg/kg): 15 mg/kg
• Patient Weight (kg): 20 kg
• Medication Available (mg): 250 mg
• Medication Volume (mL): 5 mL

Using the calculator:

1. Total Dose Needed = 15 mg/kg × 20 kg = 300 mg
2. Concentration = 250 mg ÷ 5 mL = 50 mg/mL
3. Volume to Administer = 300 mg ÷ 50 mg/mL = 6 mL

Therefore, 6 mL of Amoxicillin suspension should be administered per dose.

Important Disclaimer:

This calculator is for educational purposes only and should not replace professional medical advice or judgment. Always double-check calculations and consult with a qualified healthcare professional before administering any medication. Patient safety is the highest priority.