01What a second swallow cannot replace
A second 50 mg the same day cannot replace missing stimulation. Once per day still caps the calendar.
If desire is gone for other reasons, that is a different visit.
02Does the tablet start an erection alone
No. Plasma is not rigidity. A 50 mg swallow on a quiet sofa does not create an erection by the clock.
Giving up at 40 minutes without stimulation writes a false miss.
03What nitric oxide release the label requires
Erection physiology on the insert starts with nitric oxide release in the corpus cavernosum during sexual stimulation. Sildenafil then slows cGMP breakdown. Without the first step, the second step has nothing to enhance.
That is why the tablet is taken about one hour before sexual activity, not one hour before a nap.
04How a quiet night is a missed trial
Two rushed swallows without arousal do not count as a failed 50 mg trial. Neither does a night after enough alcohol that desire is gone.
The next talk about 100 mg needs honest nights, not quiet ones.
05When 25-50 mg still needs the same cue
A 25 mg start is not a 'weaker spontaneous' tablet. A 50 mg start is not a stronger automatic one. Both need stimulation.
The sildenafil 25-50 mg vault repeats that on the monograph.
06Why plasma is not rigidity
Fasted median Tmax near 60 minutes means the drug is often in the blood. It does not mean an erection has started. The RigiScan work that supported efficacy used visual sexual stimulation.
About one hour, window to 4 is the clock. This page is the cue.