Physicochemical characterization of solid dispersion systems of tadalafil with poloxamer 407 VIKRANT VYAS

the treatment of erectile dysfunction (1). It is a selective, potent and reversible competitive inhibitor of the enzyme phosphodiesterase-5 (PDE5), which causes inactivation of cyclic guanosine monophosphate (cGMP) (2). Due to longer duration of its action (approximately 36 hours) and minimum potential to cause vision abnormalities, tadalafil has gained wide clinical acceptance. However, it has very low aqueous solubility (practically insoluble), which leads to its poor dissolution in the gastrointestinal tract, resulting in variable bioavailability. Polymorphism may be the major cause of low aqueous solubility of tadalafil. Poor bioavailability often results in limited or irreproducible clinical response of the drug. It was therefore undertaken to develop effective methods for improvement of the dissolution rate of tadalafil. Many methods have been reported for the enhancement of aqueous solubility and dissolution rate of poorly water-soluble drugs, including the use of surfactants (3), in-