¹Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, Nashville, Tennessee, USA

Correspondence: SH. Francis, Department of Molecular Physiology and Biophysics, Ph.D., Light Hall Room 702, Vanderbilt University School of Medicine, Nashville, TN 37232-0615, USA E-mail: sharron.francis@vanderbilt.edu

Received 18 March 2003; Accepted 22 May 2003.

Abstract

Sildenafil, the active ingredient in Viagra™, ahs been purified from commercially available tablets. The purification, using Sephadex G25 chromatography under conditions of low ionic strength, is simple and inexpensive. Sildenafil purified according to this protocol has been characterized with respect to its IC₅₀ for PDE5, its ultraviolet absorption profile, and by collision-induced dissociation fingerprinting, positive ion nanospray, and MALDI mass spectrometry. Tritated sildenafil (6 Ci/mmol) was prepared commercially using the sildenafil purified by this protocol and was verified to retain the potency of unlabeled sildenafil. This protocol and similar procedures will allow investigators to easily isolate sufficient amounts of sildenafil or other PDE5 inhibitors for conducting biochemical and in vitro studies of drug action.