Abstract
Tadalafil is an oral selective phosphodiesterase type-5 inhibitor with demonstrated efficacy and safety that is used to treat erectile dysfunction. The purpose of this study is to compare the pharmacokinetic properties of tadalafil after conventional oral tablet administration and novel intranasal administration in beagle dogs. Fourteen 13-month-old male beagle dogs were randomly divided into two groups, and were given 5 mg tadalafil orally or intranasally in a parallel design. Blood samples were collected before and 0.5, 1, 1.5, 2, 4, 6, 8, 12, 24, and 36 h after administration. The plasma concentration of tadalafil was determined via liquid chromatography-tandem mass spectrometry (LC-MS/MS). The systemic exposure and absorption rate of tadalafil were significantly greater in the intranasal administration group than in the oral administration group. A one-compartment model with first-order absorption and elimination was sufficient to explain the pharmacokinetic characteristics observed after both oral and intranasal administration. This study indicates that the development of tadalafil nasal delivery systems is feasible and may lead to better results than the conventional oral route.
Highlights
Tadalafil is a selective inhibitor of phosphodiesterase type-5 (PDE5), an enzyme that inactivates cyclic guanosine monophosphate, and has demonstrated efficacy and safety as an oral therapy for erectile dysfunction (ED) [1,2]
Tadalafil has a greater selectivity for PDE5 than sildenafil, the first approved PDE5 inhibitor, and one of the most widely used PDE5 inhibitors worldwide [3]
The original formulation of tadalafil was released in 2003 as a film-coated tablet for oral administration [5]. This formulation has been inconvenient for patients, as it must be swallowed with water
Summary
Tadalafil is a selective inhibitor of phosphodiesterase type-5 (PDE5), an enzyme that inactivates cyclic guanosine monophosphate (cGMP), and has demonstrated efficacy and safety as an oral therapy for erectile dysfunction (ED) [1,2]. Tadalafil has a prolonged half-life, with a low volume of distribution, slow hepatic clearance, and approximately 80% bioavailability in human. The original formulation of tadalafil was released in 2003 as a film-coated tablet for oral administration [5]. This formulation has been inconvenient for patients, as it must be swallowed with water. As ED is frequently associated with depression, increased anxiety, poor self-esteem, and compromised interpersonal relationships [6], ED patients require a treatment that has a rapid onset and a long half-life, allowing for easy administration
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