Short answer: Not in the usual sense. The Viagra label has no schedule: it is taken as needed, about 1 hour before sexual activity, anywhere from 30 minutes to 4 hours before. The label says the most it should be taken is once per day, so a second tablet the same day is not a catch-up option.
| Situation | What the label says |
|---|---|
| Schedule | As needed, about 1 hour before sexual activity (2.1) |
| Window | 30 minutes to 4 hours before sexual activity (2.1) |
| Most per day | Once per day (2.1) |
| Usual dose | 50 mg; may go up to 100 mg or down to 25 mg (2.1) |
| Half-life | About 4 hours (12.3) |
No, because Viagra is not taken on a schedule. Section 2.1 says the usual dose is 50 mg taken as needed, approximately 1 hour before sexual activity, and that it may be taken anywhere from 30 minutes to 4 hours before. The Patient Information says the same.
Section 2.1 says the maximum recommended dosing frequency is once per day, and the Patient Information says do not take Viagra more than 1 time a day. The label gives no exception for a dose that was taken too early or did not seem to work.
Section 12.3 says sildenafil and its active metabolite both have terminal half-lives of about 4 hours. The Patient Information adds that after a high-fat meal Viagra may take a little longer to start working.
Daily Cialis (tadalafil) is the scheduled option with its own missed-dose instruction. See the Cialis missed-dose page for that rule.
This page summarizes FDA labeling. It is not personalized medical advice; confirm what to do with your prescriber or pharmacist.