{"id":3901,"date":"2022-10-25T08:34:02","date_gmt":"2022-10-25T08:34:02","guid":{"rendered":"https:\/\/modafinil.pl\/?post_type=product&p=3901"},"modified":"2026-10-03T05:41:06","modified_gmt":"2026-10-03T05:41:06","slug":"sildenafil-citrate","status":"publish","type":"product","link":"https:\/\/modafinil.pl\/en\/sklep\/sildenafil-citrate\/","title":{"rendered":"Sildenafil Citrate (CAS 171599-83-0) \u2014 Chemical Reagent 1000 mg, Purity \u2265 99%"},"content":{"rendered":"

Sildenafil citrate<\/strong> (a salt of citric acid and sildenafil), crystalline powder, 1000 mg package in a sealed aluminum zip-lock bag. The material is intended exclusively for in vitro laboratory and analytical research<\/strong>. The product is not intended for human or animal consumption<\/strong>, and is not a medicinal product, dietary supplement, foodstuff, or cosmetic.<\/p>\n

Three Different Entities That Must Not Be Confused<\/h2>\n

Sildenafil is one of the most frequently confused entries in catalogs of this type, because the same chemical name simultaneously functions as the active ingredient of widely known medicinal products distributed through pharmaceutical channels<\/strong>. Three contexts, three entirely different legal statuses:<\/p>\n\n\n\n\n\n\n\n
Separating the layers: substance \u2014 medicinal product \u2014 reagent<\/caption>\n
Entity<\/th>\nWhat it is<\/th>\nWhat it concerns<\/th>\n<\/tr>\n<\/thead>\n
Chemical substance
sildenafil citrate, CAS 171599-83-0<\/th>\n		A chemical concept \u2014 the salt of the sildenafil molecule with citric acid. On its own it is neither a drug nor a reagent; its status is conferred by the form in which it was manufactured and approved.<\/td>\nchemistry, substance registries<\/td>\n<\/tr>\n
Medicinal product
including Viagra, Revatio, Caverta<\/th>\n		Pharmaceutical preparations: a defined pharmaceutical form and strength (active ingredient concentration), manufacturing under GMP, registration documentation, and safety oversight. Registered in various countries for two separate indications (erectile dysfunction and pulmonary arterial hypertension, under separate trade names). It is these preparations that the clinical trials involving human subjects<\/strong> cited in the literature concern.<\/td>\ntherapeutics, pharmaceutical trade<\/td>\n<\/tr>\n
Chemical reagent
the material offered here<\/th>\n		A material for laboratory and analytical work. It does not have, and cannot have, approval for use in humans or animals<\/strong> \u2014 it has no pharmaceutical form or medicinal product documentation.<\/td>\nanalytics, chemistry, reference standards<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The consequence is unambiguous.<\/strong> The research results cited later on this page were obtained either using a registered medicinal product<\/strong> (clinical trials involving human subjects), or under conditions of an analytical or environmental experiment<\/strong>, in which the substance was treated as an object of determination, not as a drug administered to an organism. None of these studies was conducted using the offered analytical reagent as a substance for consumption<\/strong>, and none of these results carries over to the way the offered material may be used. The reagent is not the form in which the substance was ever administered to humans, and it cannot be used in that way.<\/p>\n

Reagent Identification Card<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n\n
Registry data and identifiers \u2014 sildenafil citrate<\/caption>\n
Systematic name (IUPAC)<\/th>\n5-[2-ethoxy-5-(4-methylpiperazin-1-yl)sulfonylphenyl]-1-methyl-3-propyl-6H-pyrazolo[4,5-d]pyrimidin-7-one; 2-hydroxypropane-1,2,3-tricarboxylic acid (salt)<\/td>\n<\/tr>\n
Common name<\/th>\nsildenafil citrate<\/td>\n<\/tr>\n
CAS Number (salt, offered material)<\/th>\n171599-83-0<\/td>\n<\/tr>\n
Molecular formula (salt)<\/th>\nC28<\/sub>H38<\/sub>N6<\/sub>O11<\/sub>S<\/td>\n<\/tr>\n
Molar mass (salt)<\/th>\n666.7 g\u00b7mol\u22121<\/sup><\/td>\n<\/tr>\n
Monoisotopic mass<\/th>\n666.2319 Da<\/td>\n<\/tr>\n
InChIKey<\/th>\nDEIYFTQMQPDXOT-UHFFFAOYSA-N<\/td>\n<\/tr>\n
SMILES<\/th>\nCCCC1=NN(C2=C1N=C(NC2=O)C3=C(C=CC(=C3)S(=O)(=O)N4CCN(CC4)C)OCC)C.C(C(=O)O)C(CC(=O)O)(C(=O)O)O<\/td>\n<\/tr>\n
PubChem CID<\/th>\n135413523<\/a><\/td>\n<\/tr>\n
ChEMBL<\/th>\nCHEMBL3650565<\/a><\/td>\n<\/tr>\n
Form<\/th>\ncrystalline powder, white to off-white<\/td>\n<\/tr>\n
Packaging<\/th>\nsealed aluminum zip-lock bag<\/td>\n<\/tr>\n
Purity<\/th>\n\u2265 99%<\/td>\n<\/tr>\n
Intended use<\/th>\nresearch reagent \u2014 not for human or animal consumption<\/strong><\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

The Molecule’s Origin: An Angina Drug That Never Reached Cardiology<\/h2>\n

The history of this molecule is among the most frequently cited examples of an accidental pharmacological discovery. The parent compound was synthesized in the late 1980s at Pfizer’s laboratories in Sandwich, United Kingdom, under the development code UK-92,480<\/strong>, as part of a program searching for phosphodiesterase type 5 (PDE5) inhibitors intended for the treatment of angina pectoris and arterial hypertension \u2014 the mechanism was meant to dilate coronary vessels by intensifying the nitric oxide\u2013cGMP pathway.<\/p>\n

The Side Effect That Changed the Direction of Research<\/h3>\n

In early phase I clinical trials, the compound did not confirm the original cardiological hypothesis \u2014 it did not show sufficient efficacy in angina pectoris. Trial participants instead reported an atypical side effect that redirected further work toward erectile dysfunction. The PDE5-inhibition mechanism and early pharmacological characterization of the compound were described by Boolell and colleagues in 1996 [1<\/a>]; the history of the research pivot itself \u2014 from cardiology to urology \u2014 is presented in a 2019 review by Goldstein et al. [2<\/a>].<\/p>\n

In March 1998, the compound was registered as a medicinal product for the treatment of erectile dysfunction \u2014 the first PDE5 inhibitor registered worldwide for this indication (trade names are listed in the table above). The same substance was later also registered under a separate trade name for a different indication \u2014 pulmonary arterial hypertension. Two different preparations, two different indications, one molecule.<\/p>\n

Why the Offered Material Is a Salt, Not the Free Base<\/h3>\n

Sildenafil as the free base (CAS 139755-83-2, formula C22<\/sub>H30<\/sub>N6<\/sub>O4<\/sub>S, molar mass 474.6 g\u00b7mol\u22121<\/sup>) and the sildenafil citrate offered on this page (CAS 171599-83-0) are two different registry records of the same active molecule<\/strong>, differing solely in salt form. The addition of citric acid increases the number of groups capable of forming hydrogen bonds and raises water solubility compared with the free base \u2014 a standard pharmaceutical technique used to facilitate oral formulation. The material offered in this catalog is the salt (citrate), consistent with the CAS number given in the title and the identification card above.<\/p>\n\n\n\n\n\n\n\n\n\n
Comparison: free base vs. sildenafil citrate<\/caption>\n
Parameter<\/th>\nSildenafil (free base)<\/th>\nSildenafil citrate (offered material)<\/th>\n<\/tr>\n<\/thead>\n
CAS Number<\/th>\n139755-83-2<\/td>\n171599-83-0<\/td>\n<\/tr>\n
Molecular formula<\/th>\nC22<\/sub>H30<\/sub>N6<\/sub>O4<\/sub>S<\/td>\nC28<\/sub>H38<\/sub>N6<\/sub>O11<\/sub>S<\/td>\n<\/tr>\n
Molar mass<\/th>\n474.6 g\u00b7mol\u22121<\/sup><\/td>\n666.7 g\u00b7mol\u22121<\/sup><\/td>\n<\/tr>\n
InChIKey<\/th>\nBNRNXUUZRGQAQC-UHFFFAOYSA-N<\/td>\nDEIYFTQMQPDXOT-UHFFFAOYSA-N<\/td>\n<\/tr>\n
PubChem CID<\/th>\n135398744<\/td>\n135413523<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Data for the free base were verified directly in PubChem (query by compound name) \u2014 included solely to distinguish it from the offered salt; the material in this catalog is exclusively the citrate with CAS number 171599-83-0.<\/em><\/p>\n

Timeline<\/h2>\n\n\n\n\n\n\n\n\n\n\n\n
Timeline: the molecule’s origin and dissemination<\/caption>\n
late 1980s<\/th>\nsynthesis of the parent compound (code UK-92,480) at Pfizer’s laboratories in Sandwich, as part of an angina pectoris research program<\/td>\n<\/tr>\n
early 1990s<\/th>\nphase I trials do not confirm cardiological efficacy; observation of an atypical side effect changes the program’s direction<\/td>\n<\/tr>\n
1996<\/th>\npublication describing the compound’s PDE5-inhibition mechanism [1<\/a>]<\/td>\n<\/tr>\n
March 1998<\/th>\nregistered as a medicinal product for the treatment of erectile dysfunction \u2014 the first PDE5 inhibitor registered for this indication<\/td>\n<\/tr>\n
2000s<\/th>\nregistration of the same substance under a separate trade name for a different indication \u2014 pulmonary arterial hypertension<\/td>\n<\/tr>\n
2003\u20132013<\/th>\ndevelopment of bioanalytical methods: HPLC-MS in biological fluids [3<\/a>], RP-HPLC in laboratory animal plasma [4<\/a>], fragmentation studies in mass spectrometry [5<\/a>]<\/td>\n<\/tr>\n
2009\u20132014<\/th>\na series of studies on detecting new sildenafil analogs as adulterants in dietary supplements [6<\/a>][7<\/a>][8<\/a>][9<\/a>][10<\/a>]<\/td>\n<\/tr>\n
2015\u20132021<\/th>\nsolid-state chemistry and analogs: improved synthesis [11<\/a>], isosteres [12<\/a>], cocrystals [13<\/a>]<\/td>\n<\/tr>\n
2021<\/th>\nforensic characterization using nuclear methods (IBA, INAA) [14<\/a>]<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Three Strands of Literature, Not One Center<\/h2>\n

Unlike molecules with a narrow, geographically concentrated body of literature, the literature on this substance is internationally dispersed and organized more around research method than around a single laboratory. For a reader searching databases, this has practical significance \u2014 it is worth combining a topical query, not just the compound name.<\/p>\n

Chemistry of the Drug and Its Derivatives<\/h3>\n

A strand covering synthesis, structural analogs, and solid-state chemistry: improved synthetic routes [11<\/a>], isosteres of the parent molecule [12<\/a>], and cocrystals that alter the substance’s physicochemical properties without changing the molecular structure [13<\/a>].<\/p>\n

Analytics and Adulterant Detection<\/h3>\n

The strand most characteristic of this molecule: sildenafil and its synthetic analogs are among the most frequently detected adulterants in dietary supplements and herbal preparations advertised as potency aids. This has given rise to a distinct area of analytical chemistry devoted to the structural identification of new analogs \u2014 by LC-UV\/LC-MS [7<\/a>], high-resolution Orbitrap mass spectrometry [9<\/a>], combined MS\/MS and NMR [10<\/a>], and a decade-long review of such detections [8<\/a>].<\/p>\n

Forensic Toxicology, Biopharmaceutics, and the Environment<\/h3>\n

The third strand covers determinations in biological fluids and environmental material: bioanalytical methods in saliva and plasma [3<\/a>][4<\/a>], forensic characterization using nuclear analysis methods [14<\/a>], and studies on the ecotoxicity of chlorination products in water [15<\/a>] \u2014 an area rarely associated with this molecule, yet genuinely present in the literature.<\/p>\n

Disclaimer for the entire section above.<\/strong> This describes the history of scientific research and the development of analytical methods. The studies involving human subjects cited in this section concerned exclusively the registered medicinal product<\/strong>, not the chemical reagent. This is not a description of the properties of the offered material<\/strong> and it cannot form the basis for any use of it outside the laboratory.<\/p>\n

Chemistry: A Salt Without a Stereogenic Center<\/h2>\n

A Molecule With No Enantiomers<\/h3>\n

Unlike some other entries in this catalog, the sildenafil core does not contain a stereogenic center<\/strong>. The sulfonamide group (S(=O)2<\/sub>N) is symmetric with respect to both oxygen atoms and does not generate chirality \u2014 unlike a sulfoxide, in which the sulfur atom bears four different substituents. The piperazine ring is symmetric, and the propyl chain on the pyrazole ring does not form a carbon with four different substituents. The practical consequence: the material does not require enantiomer separation or enantioselective methods when confirming identity \u2014 this simplifies standard qualification compared with compounds having a sulfoxide stereogenic center.<\/p>\n

Physicochemical Characterization of the Salt and Its Implications<\/h3>\n\n\n\n\n\n\n\n\n\n\n\n
Computed descriptors and their analytical significance \u2014 sildenafil citrate<\/caption>\n
Parameter<\/th>\nValue<\/th>\nWhat this means<\/th>\n<\/tr>\n<\/thead>\n
Partition coefficient (XLogP)<\/th>\nno computed value available in the source used<\/td>\nwe do not extrapolate from the free base \u2014 data are given only where verified for the salt itself<\/td>\n<\/tr>\n
Topological polar surface area (TPSA)<\/th>\n250 \u00c52<\/sup><\/td>\nvery high \u2014 an effect of adding the citric acid moiety; indicates good water solubility<\/td>\n<\/tr>\n
Hydrogen bond donors<\/th>\n5<\/td>\nthe sum of groups from the sildenafil molecule and from citric acid \u2014 the free base alone has fewer<\/td>\n<\/tr>\n
Hydrogen bond acceptors<\/th>\n15<\/td>\na high number typical of polycarboxylic acid salts<\/td>\n<\/tr>\n
Rotatable bonds<\/th>\n12<\/td>\na flexible structure \u2014 several possible conformations in solution<\/td>\n<\/tr>\n
Heavy atoms<\/th>\n46<\/td>\na large molecule for an analytical standard \u2014 relevant when interpreting high-resolution MS spectra<\/td>\n<\/tr>\n
Solubility<\/th>\ngood in water and DMSO, poorer in nonpolar solvents<\/td>\nthe salt form was chosen partly for this reason \u2014 the opposite of many lipophilic reagents in this catalog<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

Fragmentation in Mass Spectrometry<\/h3>\n

This molecule’s behavior under electrospray ionization is atypical: direct intramolecular gas-phase transfer reactions are observed during fragmentation, described in detail for sildenafil and its thio-analogs [5<\/a>]. For a laboratory implementing LC-MS\/MS methods, this has practical significance \u2014 the fragmentation spectrum cannot always be predicted by the simple additive rule known from other compound classes, as was also described in the structural identification of new sildenafil analogs by high-resolution Orbitrap spectrometry [9<\/a>].<\/p>\n

Nomenclature and Identifiers<\/h2>\n