Short answer: The Fosamax label says that if you miss a once-weekly dose, take one tablet on the morning after you remember. Do not take two tablets on the same day, and go back to taking one tablet a week on your usual day. The Patient Information says not to take it later in the day.
| Situation | What the label says |
|---|---|
| Schedule | 70 mg once weekly (or 10 mg daily) for osteoporosis treatment (2.1) |
| Missed the weekly tablet | Take one on the morning after you remember (2.8) |
| Later the same day | Do not take it (Patient Information) |
| Doubling up | Never 2 tablets on the same day (2.8) |
| After catching up | Return to your usual weekly day (2.8) |
Section 2.8 says that if a once-weekly dose is missed, take one dose on the morning after you remember. Do not take two doses on the same day, and return to one dose a week on your chosen day. The Patient Information adds: do not take it later in the day.
Example: your Fosamax day is Sunday and you remember on Tuesday afternoon. Under the label you would take one tablet Wednesday morning, then your next one on Sunday as usual.
Section 2.6 says to take Fosamax when you get up for the day, with 6 to 8 ounces of plain water only, at least 30 minutes before the first food, drink or other medicine, and not to lie down for at least 30 minutes afterwards. A tablet taken later in the day after eating does not follow those instructions, which is why the label sends a missed dose to the next morning.
Alendronate is stored in bone. The label estimates its terminal half-life in humans at more than 10 years (section 12.3), so one late tablet does not undo treatment. The bigger risk is missing many weeks without noticing.
This page summarizes FDA labeling. It is not personalized medical advice; confirm what to do with your prescriber or pharmacist.