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Duration of action
Among the three PDE5 inhibitors, the half-life and thus duration of action is the pharmacologic parameter that is the most strikingly dissimilar. The half-life of tadalafil is 17.5 hours in normal healthy men and 21.6 hours in elderly men, while the half-lives of sildenafil and vardenafil are similar at 4 hours. This longer half-life provides [...]
Dosing and absorption Tadalafil (Cialis)
Recommended starting doses of tadalafil are 10 mg for on-demand dosing and 2.5 mg for once-daily dosing, and these doses can then be titrated up or down according to the efficacy and tolerability. It is absorbed as a low-solubility and high-permeability, or Class 2, drug within the FDA Biopharmaceuticals Classification System. With oral ingestion, after [...]
Phosphodiesterase selectivity
Tadalafil is at least 9000 times more selective for PDE5 than most of the other families of PDEs, with the exception of PDE11. PDE11 is found in the testes and prostate; however, despite partial inhibition of PDE11 by tadalafil at therapeutic doses, clinical significance of this observation has yet to be fully understood. A study [...]
Background on outcome measures
Although the effectiveness of PDE5 inhibitors on such intermediate objective outcomes as penile rigidity through penile plethysmography with the RigiScan device (Dacomed Corporation, Minneapolis, MN, USA) has been studied, measuring the therapeutic effectiveness of tadalafil (Cialis Professional) is more accurately defined through an integration of the patient’s reported treatment response and tolerability with the reported [...]
Tadalafil pharmacology
The three available PDE5 inhibitors share a similar mechanism of action, but they have structural, pharmacologic, and clinical differences. The molecular structure of tadalafil is available in Figure 1. Tadalafil’s molecular structure is different than the similar structures of generic sildenafil and generic vardenafil. All three have a heterocyclic nitrogen-containing doublering system, with a central [...]
History of the development of tadalafil
The Bothell, Washington-based pharmacologic research company ICOS Corporation was started in 1990, and it began the initial cardiovascular testing of a PDE5 inhibitor called IC351 in 1993. Meanwhile, sildenafil citrate (sildenafil) was discovered to cause improved erectile function as a side effect in a trial testing its efficacy for the treatment of angina pectoris in [...]
Efficacy of Tadalafil
Tadalafil is an efficacious treatment for ED of all severities and etiologies. The largest data series exist for the general ED population with mild to moderate ED, but tadalafil has also been shown to be an effective treatment for difficult-to-treat ED such as more severe, organic ED evaluated in tertiary care centers, ED secondary to [...]
