Cialis Onset of Action & Tadalafil Levels Demystified

Various clinical studies have proved that Cialis(tadalafil) lasts upto 36 hours. This ‘window of action’ is a significant leap from what Viagra/Sildenafil has clinically exhibited. Lets look at the concentration of the medicine in the bloodstream at various times to understand its window of action.

The graphs(images) released by Eli Lilly was a poor black-white image that needed the users to exercise some imagination to understand the plasma concentration values.

We took their graph and carefully “plotted to scale” to produce an interactive line-graph where-in you can now hover over the points to see the specific tadalafil levels at different intervals.

Deductions from the graph

  • The reason for Cialis'(tadalafil) long window of action(36 hours according to Eli Lilly) is its slow withdrawal from the body.
  • The peak tadalafil plasma levels occurs at around 2 hours. This would apply for most men.
  • From the graph it appears that high concentrations of tadalafil occurs from 1hr to 6hr after ingestion. This is the time when you get the maximum help. So if you expect to get some “action” at 11pm, then it maybe a good idea to take the medication at around 9pm. Sure, it does give you a 36hr window according to clinical studies, but the concentration of the medicine is highest from 1-6 hours – so why not put that to use.
  • The peak level is around 325 and occurs at around the 2hour mark and it becomes about 162 around 17.5 hours. This is the half-life of the medicine.
  • Eli Lilly claims a 36 hour efficacy for the standard 20mg dose. From the graph, the tadalafil level at 36 hours is about 105ug/L. So we suspect they consider 105ug/l as the minimum tadalafil level required by most men to benefit from the medicine.
  • Some men report that Cialis helped them the 3rd evening (around 48 hours). Looking at the graph, there is still about 18% of the medicine in the bloodstream at the 48hour mark. It seems less and way below the minimum level we deduced above. Perhaps men who feel it helps them on the 3rd day are the ones who are very receptive to the medication and should consider milder doses.



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