Steady state and accumulation

A single-dose half-life curve is only part of the picture. Many real uses involve repeated dosing. When doses overlap, the concentration-time curve becomes the sum of multiple decays.

Accumulation in plain language

If you take another dose before the previous dose has mostly declined, the remaining amount adds to the new dose. That overlap is called accumulation. Longer half-lives produce more overlap for the same dosing interval.

Steady state as a balance

In a simplified first-order model, steady state is reached when the amount entering per interval equals the amount eliminated per interval. The curve still rises and falls within each interval, but the peaks and troughs stop drifting upward.

The “4–5 half-lives” rule of thumb

A common approximation is that it takes about 4–5 half-lives for a first-order process to get close to its long-run behavior. This is not a guarantee and does not apply cleanly to multi-compartment kinetics, variable dosing, or changing physiology.

What HalfLifeDB does and does not do

• HalfLifeDB can visualize a single-dose decay.
• HalfLifeDB does not currently model repeated dosing schedules or titration.
• HalfLifeDB is not a dosing tool and does not provide medical advice.

If you want a deeper conceptual explanation of the equation, see half-life math.