Rimonabant is a synthetic small-molecule cannabinoid receptor type 1 (CB1) antagonist, also known as SR141716 or SR141716A. It was developed as an anti-obesity pharmaceutical and selectively targets the CB1 receptor. PubChem identifies Rimonabant as a CB1 receptor antagonist/inverse agonist with molecular formula C22H21Cl3N4O and molecular weight 463.8 g/mol.
Rimonabant was previously marketed as Acomplia in the European Union. The European Commission granted marketing authorization in 2006, but the authorization was suspended in November 2008 and formally withdrawn on 16 January 2009 following safety concerns, particularly psychiatric adverse effects.
Accordingly, Rimonabant should not be presented as a currently authorized anti-obesity medicine in the EU. It remains a chemically characterized pharmaceutical compound of interest for analytical, reference-standard and research applications.
Rimonabant is a chlorinated pyrazole carboxamide compound. Its chemical name is 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-N-(piperidin-1-yl)-1H-pyrazole-3-carboxamide. PubChem lists CAS No. 168273-06-1, formula C22H21Cl3N4O, and molecular weight 463.8 g/mol.
| Property | Details |
|---|---|
| Product Name | Rimonabant |
| API Name | Rimonabant |
| CAS Number | 168273-06-1 |
| Molecular Formula | C22H21Cl3N4O |
| Molecular Weight | 463.8 g/mol |
| Alternative Name | SR141716 / SR141716A |
| FDA UNII | RML78EN3XE |
| Category | Small-Molecule Pharmaceutical API |
| Pharmacological Class | CB1 Cannabinoid Receptor Antagonist |
| Former Therapeutic Application | Anti-obesity |
| Appearance | Off-white to white crystalline solid/powder |
| Water Solubility | Very low |
| Organic Solubility | Soluble/freely soluble in selected organic solvents |
PubChem reports an experimental solubility of approximately 2.00 × 10⁻³ g/L and identifies Rimonabant as a solid.
Rimonabant is a highly lipophilic, chlorinated pyrazole derivative. PubChem reports an XLogP3-AA value of 6.5, hydrogen-bond donor count of 1, hydrogen-bond acceptor count of 3, four rotatable bonds and a topological polar surface area of 50.2 Ų.
The compound exists in different crystalline forms and can also form solvates and hydrates. Scientific studies have identified at least two closely related polymorphic modifications, with reported melting transitions around 156°C. Rimonabant monohydrate has also been structurally investigated.
This solid-state behavior is important when controlling the pharmaceutical material because crystal form, hydration and solvation can influence analytical results and physical properties.
| Parameter | Value |
|---|---|
| Active Compound | Rimonabant |
| Molecular Formula | C22H21Cl3N4O |
| Molecular Weight | 463.8 g/mol |
| XLogP3-AA | 6.5 |
| H-Bond Donors | 1 |
| H-Bond Acceptors | 3 |
| Rotatable Bonds | 4 |
| Topological Polar Surface Area | 50.2 Ų |
| Physical State | Solid |
| Appearance | White/off-white crystalline material |
| Water Solubility | Approximately 0.002 g/L reported experimentally |
| Primary Target | Cannabinoid CB1 receptor |
Rimonabant was developed primarily for the management of obesity and associated metabolic risk factors through antagonism of the CB1 receptor.
The former EU product Acomplia was authorized as an adjunct to diet and exercise for obese patients or overweight patients with associated risk factors such as type 2 diabetes or dyslipidaemia.
However, the EMA concluded that the benefits no longer outweighed the risks and recommended suspension of the marketing authorization in 2008. The authorization was subsequently withdrawn in January 2009.
Therefore, current Rimonabant API applications should be described carefully as:
It should not be marketed as an actively approved anti-obesity medicine.
Rimonabant API quality assessment can include identity, assay/purity, related substances, moisture, residual solvents and physical-form characterization.
Published manufacturing literature reports a Rimonabant preparation with 99.0% HPLC purity, 98.47% titrimetric assay, and loss on drying of 0.0% for the reported batch. The same process reported a melting point of 154–155°C. These are process/analytical results rather than a universal pharmacopoeial API specification.
A separate commercial reference material reports >99% purity and an off-white crystalline powder, while its sample COA reports 99.5% purity and loss on drying of NMT 0.5%.
Because different crystalline forms of Rimonabant have been documented, melting-point values from commercial sources should not automatically be treated as a universal release specification.
Typical analytical controls include:
Rimonabant is a specialized synthetic pharmaceutical compound requiring control of chemical purity, related substances and solid-state form.
A suitable Rimonabant API manufacturing and analytical program should include:
Because Rimonabant is no longer an EU-authorized medicinal product, regulatory status and intended use should be considered carefully when sourcing or supplying the material.
Rimonabant API should be packaged in suitable well-closed pharmaceutical containers, protected from excessive moisture, heat and light.
Storage conditions should be established from the validated stability data for the specific material and solid form. Commercial research material is commonly supplied under controlled storage conditions, but no single universal regulatory storage temperature was identified that should be applied to every Rimonabant API batch.
Packaging may include:
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | NLT 99.0% |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |
| Heavy Metals | NMT 10 ppm |
| Melting Point | 154–157°C |
| Solubility | Approximately 0.002 g/L in water; soluble in selected organic solvents |