The titration schedule is a tolerability instrument, not an efficacy one. Nothing in the ladder is there to make the compound work better; every step exists to make the gastrointestinal adverse-event curve survivable.
Steady state, worked: with a half-life of about seven days and weekly administration, the accumulation ratio is roughly 1/(1 − 0.5) = 2, and you get to within about 97 per cent of steady state after five half-lives, so around thirty-five days — five weeks — after any dose change. A four-week step interval therefore has you escalating at roughly 94 per cent of the previous dose’s steady state, which is close enough to be sensible and not so close as to be conservative.
Weekly dosing accumulation, 7-day half-life
| Week | Fraction of steady state | Trough as × dose |
|---|
| 1 | 50 % | 0.50 |
| 2 | 75 % | 0.75 |
| 3 | 88 % | 0.88 |
| 4 | 94 % | 0.94 |
| 5 | 97 % | 0.97 |
| 6 | 98 % | 0.98 |
This is why a four-week step interval is approximately, but not exactly, steady state.
More usefully, missing a dose by three days on a weekly schedule takes the trough down by less than a factor of 1.35, which is well inside the variation you would see between two on-time weeks. Missing it by five or more days is where the label instructions start to differ between agents, and the reason is how close the next scheduled dose is rather than any mechanistic threshold.
Escalate on tolerability, hold when it costs you, and do not confuse a flattening curve with a failing drug.