Dosing Interval Designer (Peak/Trough Ratio)

Dosing Interval Designer (Peak/Trough Ratio) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Health
Input types: select, number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

Dosing Interval Designer calculates the dosing interval from a target steady-state peak/trough ratio or calculates the resulting ratio from a chosen interval. It uses linear one-compartment kinetics at steady state with a fixed dose and interval, and is not medical advice.

When to use

Estimate the dosing interval needed for a target peak/trough concentration ratio.
Calculate within-interval fluctuation for a proposed dosing interval.
Check pharmacokinetic assumptions using a known elimination half-life.

How it works

1Enter the elimination half-life in hours.
2Choose From peak/trough ratio → τ or From τ → peak/trough ratio.
3Enter either the target ratio or dosing interval, depending on the selected mode.
4The tool calculates the result using k = ln2 / t½ and returns JSON with the interval, ratio, elimination rate constant, method, and model details.

Use cases

Pharmacokinetic modeling of steady-state concentration fluctuation.
Comparing proposed dosing intervals using a known half-life.
Teaching or checking the relationship between half-life, interval, and peak/trough ratio.

Examples

1. Design a 12-hour interval from a target ratio

Pharmacokinetics student

Background

A one-compartment linear model uses a drug half-life of 6 hours and requires a steady-state peak/trough ratio of 4.

Problem

Find the dosing interval that produces the target ratio.

How to use

Select From peak/trough ratio → τ, enter a half-life of 6 hours and a ratio of 4, then calculate.

{"mode":"ratio-to-tau","halfLife":6,"ratio":4,"decimalPlaces":4}

Outcome

The tool returns a dosing interval of 12 hours and an elimination rate constant of approximately 0.1155 h⁻¹.

2. Evaluate fluctuation at an interval equal to half-life

Pharmacokinetics analyst

Background

A proposed dosing interval is 8 hours for a drug with an 8-hour elimination half-life.

Problem

Determine the resulting steady-state peak/trough ratio.

How to use

Select From τ → peak/trough ratio, enter a half-life of 8 hours and an interval of 8 hours, then calculate.

FAQ

What does this tool calculate?

It calculates a dosing interval from a target peak/trough ratio or calculates the peak/trough ratio from a chosen interval.

What is the peak/trough ratio?

It is the steady-state concentration ratio Cmax,ss/Cmin,ss across one dosing interval.

What inputs are required?

A positive half-life is always required. Mode A requires a ratio greater than 1, while Mode B requires a positive dosing interval.

Is the peak/trough ratio the accumulation index?

No. It describes fluctuation within one interval and is not the accumulation index.

Does this provide medical advice?

No. The calculation is for pharmacokinetic modeling and should not be used as medical advice.

{"mode":"tau-to-ratio","halfLife":8,"interval":8,"decimalPlaces":4}

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Design a 12-hour interval from a target ratio

2. Evaluate fluctuation at an interval equal to half-life

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