Daily: Daily tadalafil is taken once per day and comes in a low dose (2.5mg or 5mg dosage), which gradually builds up in your system. This means that you can be ready for sex at any time instead of waiting for a pill to kick in.
As-Needed: Take the as-needed (or "episodic") dose of tadalafil when you want to be ready for the bedroom. Take this pill before you plan to have sex (for most men it reaches peak effect 2 hours after it's taken) and be aware that its effects can last for up to 36 hours. It comes in a higher dose than daily-use tadalafil (5mg, 10mg or 20mg dosages) so it's best to avoid using it on several consecutive days.