Missed dose (revision 3)
Old revision·10:13, 17 Oct 2024·Chromatokid
| Missed dose | |
|---|---|
| Governing quantity | Half-life relative to dosing interval |
| Weekly agents | Long half-life; concentration falls slowly |
| Daily agents | Steady state re-established within days |
| Topic infobox · conventions | |
A missed dose is a scheduled administration that is not taken. How much it matters depends almost entirely on the ratio between the drug's half-life and its dosing interval: a long half-life relative to the interval means concentrations fall slowly and a single omission changes exposure little.[1]
For a weekly agent with a half-life of several days, the concentration at the end of a normal dosing interval has fallen to a substantial fraction of its peak, and a missed week extends that decline rather than producing a sudden loss of exposure. For a daily agent with a half-life of hours, a missed day is a larger proportional change but is corrected within a day or two of resuming.[2]
The governing arithmetic
[edit]After a dose, concentration falls by half each half-life. For a peptide with a half-life of seven days on a weekly schedule, trough concentration is about half the peak and steady-state accumulation is roughly two-fold. Omitting one dose allows a further halving before the next dose is taken.[2]
| Half-life | Interval | Fall over one missed interval |
|---|---|---|
| ≈7 days | Weekly | To about half |
| ≈5 days | Weekly | To about two fifths |
| ≈13 hours | Daily | To a few per cent |
| ≈2.4 hours | Twice daily | Essentially complete |