Formoterol Fumarate API is the fumarate salt of formoterol, a long-acting selective β₂-adrenergic receptor agonist used in pharmaceutical formulations for bronchodilator therapy. Formoterol Fumarate is supplied predominantly as the dihydrate and has the molecular formula (C₁₉H₂₄N₂O₄)₂·C₄H₄O₄·2H₂O and molecular weight 840.92 g/mol. The anhydrous form has a molecular weight of 804.89 g/mol. The USP monograph specifies 98.5%–101.5% formoterol fumarate on an anhydrous basis.
Formoterol Fumarate is a racemic formoterol fumarate salt containing two formoterol molecules for each molecule of fumaric acid, with two water molecules in the dihydrate form. FDA's substance record confirms the molecular composition and racemic stereochemistry.
Formoterol Fumarate Dihydrate has CAS Number 183814-30-4, while the anhydrous form is identified by CAS Number 43229-80-7. The dihydrate has a molecular weight of 840.92 g/mol and the anhydrous form has a molecular weight of 804.89 g/mol.
The USP specification requires an assay of 98.5%–101.5%, calculated on the anhydrous basis. USP also specifies pH 5.5–6.5, water 4.0%–5.0%, and residue on ignition NMT 0.1%.
The USP related-substances procedure includes specific limits for Formoterol Related Compounds A, C, D and I, together with limits for unspecified impurities.
Formoterol Fumarate is used as an active pharmaceutical ingredient in inhalation formulations and acts as a long-acting β₂-adrenergic agonist with bronchodilator activity.
Formoterol Fumarate API should be manufactured and tested according to the applicable pharmacopoeial or approved manufacturer specification. Batch-specific quality should be confirmed using the relevant Certificate of Analysis (CoA).
| Parameter | Specification |
|---|---|
| Appearance | White to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 98.5% – 101.5% |
| Loss on Drying | NMT 5.0% |
| Residue on Ignition | NMT 0.1% |
| Heavy Metals | NMT 20 ppm |
| pH (1% Solution) | 5.5 – 6.5 |
| Melting Point | About 231°C (decomposition) |