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To the Editor: An estimated 20 million men worldwide have been prescribed sildenafil for erectile dysfunction, and there is a growing market in "natural" alternatives.¹ We analyzed the chemical content of one such product, Actra-R_x, which has been advertised as "100% natural."^2-6

Methods
We used mass spectrometry to analyze samples from a bottle of Niagra Actra-R_x and a bottle of Actra-R_x (Body Basics, Los Angeles, Calif) for the presence of sildenafil. The first bottle was purchased as an over-the-counter natural product in a local store. The second bottle was purchased directly from the vendor via the Internet (http://www.bodybasics.net) and was placed under a chain of custody to protect its integrity. A total of 3 random tablets were analyzed from each of the 2 bottles. The reference material, sildenafil citrate, was obtained from a 25-mg tablet purchased from a local pharmacy with a physician's prescription. Samples from both bottles (Niagra Actra-R_x and Actra-R_x) were tested under full-scan mode liquid chromatography mass spectrometry (LC/MS) and compared with the reference sildenafil citrate. Technical details of the analysis are available from the authors.

Results
The full-scan spectra of the capsules purchased from the vendor showed retention time, fragmentation pattern, ion ratios, and pseudomolecular ion [M + H]⁺ 475 identical to that of the sildenafil reference material. Figure 1 represents a typical chromatographic profile of a single specific random capsule; the other 5 capsules yielded identical results. Figure 2 represents a full-scan mass spectra of a single capsule; all other capsules yielded identical results.

View larger version (12K): [in this window] [in a new window] Figure 1. Chromatographic Separation of Sildenafil and Internal Standard by Liquid Chromatography Mass Spectrometry

View larger version (23K): [in this window] [in a new window] Figure 2. Liquid Chromatography Mass Spectrometry Full-Scan Spectra of Reference Sildenafil Citrate and Niagra Actra-Rx A, Spectra of sildenafil from Niagra Actra-Rx showing a matching spectrum with pseudomolecular ion [M + H]+ 475. B, Spectra of sildenafil citrate from Viagra tablet showing pseudomolecular ion [M + H]+ 475 and fragmentation pattern.

The amount of of sildenafil in the capsules from the second bottle (ie, that under chain of custody) was quantified by LC/MS and compared with the reference sildenafil standard. The average values of each of 3 capsules tested in triplicate were 55.2, 52.8, and 56.7 mg per capsule.

Comment
We found that samples of a "100% natural product" for erectile dysfunction contained an average of 55 mg of sildenafil per capsule. The use of such nonprescription substances may present health risks for individuals with contraindications to the use of sildenafil.

Acknowledgment: We thank Luis Valle Martinez, PhD, at El Centro de Estudios para del Desarrollo de la Quimica at the University of Chile.

Alberto J. Sabucedo, PhD
sabucedo{at}fiu.edu
Department of Chemistry and Biochemistry
International Forensic Research Institute

Mauricio A. Gutierrez, MA
School of Journalism and Mass Communication

Keith C. Mueller, BS; Brandi L. Bellissima, BS; Ya-Li Hsu, MS; Stefan Rose, MD; Kenneth G. Furton, PhD
Department of Chemistry and Biochemistry
International Forensic Research Institute
Florida International University
Miami

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Letters Section Editor: Stephen J. Lurie, MD, PhD, Senior Editor.

JAMA. 2004;291:560-562.