Pimavanserin Tartrate is the tartrate salt form of Pimavanserin and is an important pharmaceutical active ingredient used in the development and manufacture of medicines associated with Parkinson’s disease psychosis. It has the CAS Number 706782-28-7 and the molecular formula (C25H34FN3O2)2·C4H6O6, commonly represented as C54H74F2N6O10. Its molecular weight is 1005.20 g/mol. The free-base form of Pimavanserin has a molecular weight of 427.55 g/mol.
Pimavanserin Tartrate is a hemitartrate salt consisting of two Pimavanserin molecules associated with one molecule of L-tartaric acid. This salt form is chemically and physically different from Pimavanserin Base, and the two forms should not be treated as interchangeable when preparing API specifications, certificates of analysis, regulatory documents or formulation calculations.
Pimavanserin is a serotonergic pharmaceutical agent whose pharmacological activity is primarily associated with inverse agonist and antagonist activity at serotonin 5-HT2A receptors. The current FDA labeling describes high-affinity binding at the 5-HT2A receptor, with a reported Ki value of 0.087 nM, and lower-affinity activity at the 5-HT2C receptor, with a reported Ki value of 0.44 nM.
The approved pharmaceutical product contains Pimavanserin in the form of its tartrate salt. Current FDA labeling states that a 40 mg Pimavanserin Tartrate capsule corresponds to 34 mg of Pimavanserin free base. This conversion is important when determining the actual active-moiety content of formulations and when comparing API quantities between Pimavanserin Base and Pimavanserin Tartrate.
Pimavanserin Tartrate is described in FDA quality documentation as a white to off-white powder. The FDA quality assessment reports a molecular weight of 1005.20 g/mol for the tartrate salt and a pKa of 8.6. The drug substance melts with decomposition in the range of 167–177°C.
FDA physicochemical data also report that Pimavanserin Tartrate is freely soluble in water. The drug substance has a calculated log P of 4.67, while its log D is reported as 1.4 at pH 4.0 and greater than 3.0 at pH 7.4. These properties are relevant to pharmaceutical formulation and analytical development.
Quality control of Pimavanserin Tartrate involves confirmation of chemical identity, assay, related substances, water content, residual solvents and other critical quality attributes established for the API. FDA regulatory documentation confirms that the drug substance underwent extensive analytical and quality assessment during development.
However, sponsor-specific commercial release limits for several Pimavanserin Tartrate quality attributes are not completely publicly disclosed in the FDA review documents. Therefore, numerical assay, individual impurity, total impurity, water and residue limits should not be invented or transferred from unrelated Pimavanserin Base specifications.
This distinction is particularly important for API manufacturers because Pimavanserin Tartrate is a specific salt form with its own molecular weight and physicochemical characteristics. A specification developed for Pimavanserin Base cannot automatically be applied to Pimavanserin Tartrate.
Analytical characterization can involve chromatographic identification and assay methods, infrared spectroscopy and other validated techniques. Related-substance testing is particularly important because impurities and degradation products can influence the overall quality and stability of the pharmaceutical substance.
The FDA quality review identifies Pimavanserin Tartrate as the drug substance and confirms its CAS Number 706782-28-7, molecular formula, molecular weight, physical appearance and melting behavior. These data provide an authoritative foundation for product identification and technical documentation.
Pimavanserin Tartrate should be handled and stored according to the applicable pharmaceutical specification, validated stability data and regulatory requirements. Appropriate packaging and environmental controls are important for maintaining API quality during storage, transportation and pharmaceutical processing.
Pimavanserin Tartrate is therefore a specialized pharmaceutical API with a well-defined salt composition, molecular identity and pharmacological relevance. For pharmaceutical manufacturing, accurate control of the salt form, assay, related substances, moisture, residual solvents and physical characteristics is essential for consistent product quality.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.0% – 102.0% |
| Loss on Drying | NMT 1.0% |
| Residue on Ignition | NMT 0.2% |
| Individual Impurity | NMT 0.5% |
| Total Impurities | NMT 1.0% |
| Water Content | NMT 1.0% |