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Updated: May 11, 2026

Thermostabilization, Expression, Purification, and Crystallization of the Human Serotonin Transporter Bound to S-citalopram

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Paroxetine hydrochloride: polymorphs and solvatomorphs.

Harry G Brittain¹

¹Center for Pharmaceutical Physics, Milford, NJ, USA.

Profiles of Drug Substances, Excipients, and Related Methodology

|May 15, 2013

Summary

Researchers evaluated the crystal forms of paroxetine hydrochloride, identifying four distinct polymorphic and four solvatomorphic structures. This study clarifies the known solid-state landscape for this important pharmaceutical compound.

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Area of Science:

Solid-state chemistry
Pharmaceutical sciences
Crystallography

Background:

Paroxetine hydrochloride is a widely used antidepressant.
Understanding its solid-state forms (polymorphs and solvates) is crucial for drug formulation and efficacy.
Previous characterization of paroxetine hydrochloride crystal forms has been fragmented.

Purpose of the Study:

To comprehensively evaluate the polymorphic and solvatomorphic landscape of paroxetine hydrochloride.
To determine the total number of authentic crystal forms discovered for paroxetine hydrochloride.
To consolidate existing knowledge on paroxetine hydrochloride's solid-state forms.

Main Methods:

Extensive literature and patent survey.
Critical analysis of reported crystal structures.
Identification and classification of distinct polymorphic and solvatomorphic forms.

Main Results:

Four genuine nonsolvated polymorphic forms of paroxetine hydrochloride have been identified.
Four fully characterized solvatomorphic forms of paroxetine hydrochloride have been documented.
The study provides a clear overview of the discovered crystal forms.

Conclusions:

The polymorphic and solvatomorphic landscape of paroxetine hydrochloride is well-defined with a total of eight characterized forms.
This consolidation aids in understanding and controlling the solid-state properties of paroxetine hydrochloride.
Further research may focus on the stability and interconversion of these identified forms.