Same drug family, different clocks: sildenafil works about 4 hours and prefers an empty stomach (per MedlinePlus: take roughly 1 hour before), while tadalafil can last up to 36 hours per the NHS and also comes as a low daily dose that removes timing entirely.
Sildenafil: no more than once in 24 hours, high-fat meals slow it. Tadalafil: food is irrelevant; daily low-dose option suits spontaneity. Shared cautions: the nitrate interaction is dangerous for both, headaches and flushing are the common side effects, and neither works without arousal. Both are generics now, so the price gap mostly closed.
What to do
Common questions
What is the difference between Viagra and Cialis?
Same family - both are PDE5 inhibitors doing the same job - but the clocks differ enough to change how you live with them. Sildenafil (Viagra): per MedlinePlus, take it about 1 hour before sexual activity (the window runs 30 minutes to 4 hours before), it lasts around 4 hours, a high-fat meal slows it down, and you should not take it more than once in 24 hours. Tadalafil (Cialis): per the NHS, its effects can last up to 36 hours - the "weekend pill" framing - food does not matter, and uniquely it also comes as a low daily dose you take at the same time every day, per MedlinePlus, which removes the timing question entirely for people with frequent or spontaneous sex. The choice tends to follow lifestyle: planned occasions lean sildenafil, spontaneity leans tadalafil or the daily version. Shared cautions: the nitrate interaction is dangerous for both, headaches and flushing are the common side effects, and neither causes automatic arousal - they support the response to stimulation. Both are generics now, so the price gap mostly closed. Pymander, a free AI doctor available 24/7 by text, can help you think through which pattern fits.