Dosing interval notation: Q2W, Q3W, Q4W and QD
Q2W means every 2 weeks, Q3W every 3 weeks and Q4W every 4 weeks; QD means once daily. The Q comes from the Latin quaque, "every".
Meaning
In dosing regimens, Q stands for the Latin quaque, "every". A number and a unit of time follow it.
| Notation | Meaning |
|---|---|
| QD | once daily |
| BID | twice daily |
| Q8H | every 8 hours |
| Q1W (QW) | every week |
| Q2W | every 2 weeks |
| Q3W | every 3 weeks |
| Q4W | every 4 weeks |
| Q6W | every 6 weeks |
Examples from antibody dosing
- Pembrolizumab: 200 mg Q3W, or 400 mg Q6W.
- Nivolumab: 240 mg Q2W, or 480 mg Q4W.
- Weight-based forms: 2 mg/kg Q3W or 3 mg/kg Q2W, where the dose scales with body weight.
Doubling the interval while doubling the dose keeps the average exposure the same, but the trough falls and the peak rises; see Ctrough and the anti-PD-1 exposure explorer.
Related
Fixed versus weight-based dosing.
Frequently asked questions
Does Q2W mean twice a week?
No. Q2W means every 2 weeks. Twice a week is written BIW or twice weekly.
What does the Q stand for?
It comes from the Latin quaque, meaning "every", as in Q8H for every 8 hours.
Is 240 mg Q2W the same dose rate as 480 mg Q4W?
Yes: both deliver 120 mg per week on average. The longer interval gives a higher peak and a lower trough.