function calculateVancoPK() {
var age = parseFloat(document.getElementById('vanco_age').value);
var weight = parseFloat(document.getElementById('vanco_weight').value);
var scr = parseFloat(document.getElementById('vanco_scr').value);
var gender = document.getElementById('vanco_gender').value;
var dose = parseFloat(document.getElementById('vanco_dose').value);
var interval = parseFloat(document.getElementById('vanco_interval').value);
if (isNaN(age) || isNaN(weight) || isNaN(scr) || isNaN(dose)) {
alert('Please enter valid numerical values.');
return;
}
// Cockcroft-Gault CrCl
var crcl = ((140 – age) * weight) / (72 * scr);
if (gender === 'female') {
crcl *= 0.85;
}
// Elimination rate constant (ke) – Matzke equation
var ke = (0.00083 * crcl) + 0.0044;
// Half life
var thalf = 0.693 / ke;
// Volume of distribution (Vd) – standard 0.7 L/kg
var vd = 0.7 * weight;
// PK calculations (Steady State One-Compartment)
// Assume 1 hour infusion time (tinf = 1)
var tinf = 1;
var peak = (dose / (tinf * vd * ke)) * (1 – Math.exp(-ke * tinf)) / (1 – Math.exp(-ke * interval));
var trough = peak * Math.exp(-ke * (interval – tinf));
// AUC24 calculation
var dailyDose = dose * (24 / interval);
var auc = dailyDose / (ke * vd);
document.getElementById('res_crcl').innerText = crcl.toFixed(1);
document.getElementById('res_ke').innerText = ke.toFixed(4);
document.getElementById('res_half').innerText = thalf.toFixed(1);
document.getElementById('res_vd').innerText = vd.toFixed(1);
document.getElementById('res_peak').innerText = peak.toFixed(1);
document.getElementById('res_trough').innerText = trough.toFixed(1);
document.getElementById('res_auc').innerText = auc.toFixed(1);
document.getElementById('vanco_results').style.display = 'block';
}
Understanding Vancomycin Pharmacokinetics
Vancomycin is a glycopeptide antibiotic primarily used to treat serious infections caused by Gram-positive bacteria, including MRSA. Because it has a narrow therapeutic index, calculating its pharmacokinetic (PK) profile is essential to maximize efficacy and minimize nephrotoxicity.
Key Parameters in Vanco PK
Creatinine Clearance (CrCl): Since vancomycin is primarily excreted by the kidneys, CrCl is the most important predictor of vancomycin clearance. This calculator uses the Cockcroft-Gault equation.
Elimination Rate Constant (ke): This represents the fraction of drug removed from the body per hour. It is directly related to the patient's renal function.
Volume of Distribution (Vd): Represents the apparent volume in which the drug is dissolved. In most adults, this is approximately 0.7 L/kg.
AUC/MIC Ratio: Modern guidelines recommend an AUC24/MIC ratio of 400 to 600 as the primary target for treating serious MRSA infections, rather than relying solely on trough levels.
Clinical Example
Consider a 70-year-old male patient weighing 80kg with a Serum Creatinine of 1.2 mg/dL. If prescribed 1250 mg every 12 hours:
ke Determination: (0.00083 × 64.8) + 0.0044 = 0.0582 hr-1.
Steady State Trough: Predicted based on the decay from the peak concentration over the 12-hour dosing interval.
Disclaimer: This calculator is for educational and clinical reference purposes only. Clinical decisions should be made by qualified healthcare professionals based on individual patient assessment and local institutional protocols.