Promethazine Hydrochloride is the hydrochloride salt of promethazine, a first-generation H1-antihistamine belonging to the phenothiazine class. It is chemically identified as N,N-dimethyl-1-(10H-phenothiazin-10-yl)propan-2-amine hydrochloride and has the molecular formula C₁₇H₂₀N₂S·HCl, corresponding to C₁₇H₂₁ClN₂S. Its molecular weight is approximately 320.88 g/mol, and its CAS Number is 58-33-3.
Promethazine Hydrochloride is an established pharmaceutical active ingredient with antihistaminic, antiemetic and anticholinergic properties. It has been used in pharmaceutical preparations for the management of allergic conditions, nausea and vomiting, motion sickness and other conditions where an H1-receptor antagonist is indicated.
The hydrochloride form is the pharmaceutical API form and should be distinguished from free-base Promethazine, which has CAS 60-87-7 and a different molecular weight. The API specification, assay basis and quality documentation should therefore always refer specifically to Promethazine Hydrochloride.
Product Name: Promethazine Hydrochloride
Synonyms: Promethazine HCl; Promethazine Hydrochloride; Promethazine hydrochloride [USP/JAN]
CAS Number: 58-33-3
Molecular Formula: C₁₇H₂₀N₂S·HCl
Molecular Weight: 320.88 g/mol
API Class: H1 Antihistamine / Phenothiazine derivative
Chemical Type: Hydrochloride salt
Appearance: White to faint yellow crystalline powder
Parent Compound: Promethazine
PubChem describes Promethazine Hydrochloride as an odorless white to faint-yellow crystalline powder and confirms CAS 58-33-3 and molecular weight approximately 320.9 g/mol.
Promethazine Hydrochloride contains a phenothiazine ring system substituted with a dimethylaminopropyl side chain. Formation of the hydrochloride salt provides the form commonly used for pharmaceutical manufacturing.
The API acts primarily as an H1 histamine-receptor antagonist and also possesses anticholinergic and sedative properties. Its pharmacological characteristics make it useful in pharmaceutical products intended for antihistaminic and antiemetic applications.
Promethazine Hydrochloride is sensitive to light, and the USP monograph specifically requires protection using tight, light-resistant containers.
Promethazine Hydrochloride is used as an active pharmaceutical ingredient in formulations intended for:
The finished dosage form, concentration and route of administration depend on the formulation and applicable regulatory approval. Promethazine Hydrochloride is used in pharmaceutical products including oral preparations and injectable products. USP maintains separate monographs for Promethazine Hydrochloride Injection and other dosage forms.
Promethazine Hydrochloride is covered by a USP-NF drug-substance monograph. The current USP-based specification states that it contains NLT 97.0% and NMT 101.5%, calculated on the dried basis.
Identification includes infrared absorption and the chloride test. The USP monograph also specifies a pH range of 4.0–5.0 using a 50 mg/mL solution, equivalent to a 1-in-20 solution.
Loss on drying is controlled at NMT 0.5%, with drying at 105°C for 4 hours. Residue on ignition is NMT 0.1%.
The USP organic-impurity procedure has been modernized to chromatographic testing. Reported related substances include promethazine sulfoxide, desmethyl promethazine, phenothiazine and unspecified degradation products. A current USP-based presentation identifies limits including promethazine sulfoxide NMT 1.0%, desmethyl promethazine NMT 0.2%, phenothiazine NMT 0.2%, and any individual unspecified degradation product NMT 0.2%.
HPLC methods are also established for determination of promethazine and its related substances, including stability-indicating methods for pharmaceutical formulations.
Promethazine Hydrochloride API manufacturing requires controlled chemical processing, purification, hydrochloride salt formation, drying and analytical testing. A qualified Promethazine Hydrochloride API manufacturer in India can support pharmaceutical development and commercial requirements with controlled manufacturing processes and batch-specific documentation.
Manufacturing controls should include raw-material qualification, process monitoring, purification, drying, physical-property control and final analytical testing.
Particular attention should be given to protection from light during processing, testing, packaging and storage because the USP monograph specifically requires light-resistant packaging.
Each batch should be evaluated against an approved specification covering identity, assay, moisture, residue on ignition, pH and related substances.
Promethazine Hydrochloride should be packed in suitable pharmaceutical containers that protect the API from moisture, contamination and light.
The USP requirement is tight, light-resistant containers.
Commercial storage conditions should be established according to validated stability data, packaging configuration and applicable regulatory requirements.
Typical documentation for Promethazine Hydrochloride API may include:
All documentation should clearly identify Promethazine Hydrochloride, CAS 58-33-3, to distinguish it from Promethazine free base and other phenothiazine APIs.
Promethazine Hydrochloride is an established antihistaminic API with recognized pharmacopoeial requirements. The current USP-based monograph specifies 97.0–101.5% assay on the dried basis, NMT 0.5% loss on drying, NMT 0.1% residue on ignition, and pH 4.0–5.0 in a 50 mg/mL solution.
A qualified Promethazine Hydrochloride API manufacturer in India can provide pharmaceutical-grade material supported by controlled manufacturing, analytical testing and batch-specific quality documentation.
| Parameter | Specification |
|---|---|
| Appearance | white to off-white crystalline powder |
| Identification | IR & HPLC compliant |
| Assay (HPLC) | 97.0–101.5%, |
| Loss on Drying | NMT 0.5% |
| Residue on Ignition | NMT 0.1% |