Understanding Trough Concentration
Trough concentration is the estimated drug level at the end of a dosing interval. It is often checked just before the next dose. This calculator uses a one compartment, first order model. The model is simple, but it is useful for planning and teaching. It can estimate a trough from a dose plan. It can also estimate a trough from a measured peak.
Why Inputs Matter
The most important inputs are dose, interval, half life, volume, and infusion time. These values describe how much medicine enters the body, how fast it leaves, and how long it has to fall before the next dose. Bioavailability is included for non intravenous dosing. Clearance can also be entered. When clearance and volume are supplied, the tool shows the related elimination rate.
Timing and Steady State
Timing matters because a sample taken early can look high. A sample taken late can look low. The calculator displays the time gap used in the decay step. It also shows an accumulation factor for repeated dosing. This helps users see why steady state troughs differ from a single dose estimate.
Reading the Result
The result should be read as an estimate, not a medical order. Real patients may have changing kidney function, fluid balance, absorption, protein binding, or interacting medicines. Those factors can change the true level. Laboratories may also report different units. Always match units before using the number.
Target Range Check
Use the target fields as a checking aid. Enter the lower and upper target values used by your service, if any. The tool will mark the result as below, within, or above that range. It does not choose a dose for a patient. It only organizes the math.
Review Assumptions
Review the assumptions before saving a report. The calculated curve assumes steady dosing and a constant elimination rate. It does not replace measured levels. It works best when doses are given on time and the sample time is known. Record missed doses, delayed infusions, or uncertain sample times in the notes field.
Reports and Notes
The export buttons help with records. The CSV file is useful for spreadsheets. The PDF file is useful for a report. Keep the timing notes with every result. A trough without timing context can be misleading. Confirm any therapeutic decision with a qualified clinician and local protocol.