Although Viagra is generally only effective for a few hours, it can still linger in your system, so wait at least 24 hours. Although you should not take Cialis and Viagra simultaneously or within 36 hours, it may be okay to alternate outside this timeframe. Erectile dysfunction (ED) affects millions of people and can significantly influence relationships and self-confidence. Many find it challenging to identify the appropriate treatment that works effectively for them. Viagra and Cialis are two well-known medications for ED, but some suggest the possibility of combining them. This combination may provide improved results for certain individuals when used cautiously under medical supervision.