Amlodipine Besylate is a third-generation dihydropyridine calcium channel blocker (CCB) originally developed by Pfizer and marketed under the trade name Norvasc®. It is one of the most widely prescribed antihypertensive drugs globally. The drug selectively inhibits L-type calcium channels on vascular smooth muscle cell membranes, reducing transmembrane calcium ion influx, thereby dilating peripheral arteries and coronary arteries to lower blood pressure and improve myocardial perfusion.
Amlodipine Besylate is characterized by its slow onset, prolonged duration of action, and high vascular selectivity. Following oral administration, peak plasma concentration is reached within 6–12 hours, with a terminal elimination half-life of 35–50 hours. Once-daily dosing achieves 24-hour stable blood pressure control. The amlodipine tablet was first approved in the United States in 1990 and subsequently launched in China in June 1994. With over 30 years of clinical use, it has accumulated the most extensive evidence among all CCB-class drugs. In 2020, Pfizer Upjohn merged with Mylan to form Viatris, to which the product rights were transferred. As a National Essential Drug List and National Reimbursement Drug List (NRDL) product, amlodipine besylate has long held a leading market share in China's domestic antihypertensive market, serving as a foundational therapy for hypertension and coronary artery disease.
Basic Information
Chemical & Pharmaceutical Properties
Reference Listed Drug (RLD)
In accordance with the Catalogue of Reference Listed Drugs for Generic Drugs published by the National Medical Products Administration (NMPA), amlodipine besylate tablets (5 mg and 10 mg) listed in the catalogue are selected as the RLD. The marketing authorization holder is Viatris (formerly Pfizer), with the trade name Norvasc®. This is the originator product marketed in China, with approval numbers GuoYaoZhunZi H10950224 (5 mg) and GuoYaoZhunZi H20093660 (10 mg), manufactured by Viatris Pharmaceuticals (Dalian) Co., Ltd.
Synthesis Process Route
The synthesis of amlodipine besylate employs the classical Hantzsch reaction route. Through years of process optimization and technological iteration, a mature and stable industrial production system has been established. The process development focus of this project is centered on three directions: yield improvement, impurity control, and cost optimization.
Hantzsch Cyclization
Starting from [2-(2,5-dimethylpyrrol-1-yl)ethoxy]ethyl acetoacetate, o-chlorobenzaldehyde, and methyl 3-aminocrotonate in isopropanol at reflux temperature, the Hantzsch reaction proceeds for approximately 20 hours with a molar feed ratio of 1:1:1. The improved process splits the conventional one-pot Hantzsch reaction into two stages—first synthesizing the Schiff base intermediate, followed by cyclization—thereby significantly enhancing reaction controllability and intermediate purity. The intermediate yield was improved from 29.12% to over 55.8%.
Deprotection & Salt Formation
The pyrrole protecting group is converted to the free amino group under hydroxylamine conditions without affecting the adjacent ester protecting groups, substantially increasing the deprotection yield. Subsequently, amlodipine free base is reacted with benzenesulfonic acid in an appropriate solvent for salt formation. Reaction temperature, addition rate, and solvent system are carefully controlled to ensure complete salt formation and acquisition of the target crystal form. The salt formation step is critical to final product quality and requires stringent control of pH and crystallization conditions.
Crude Product Purification
Ethyl acetate and n-hexane are employed as crystallization solvents. By controlled cooling (gradient temperature reduction) and optimized stirring speed, amlodipine besylate crystals of high purity and uniform particle size are obtained. Key control parameters during purification include related substances content, residual solvents, and crystal form consistency, ensuring the finished product meets pharmacopoeia specifications. The optimized overall yield stabilizes above 45%.
Primary production equipment includes: glass-lined stirred reaction vessels, concentration tanks, crystallization vessels, centrifuges, and vacuum drying ovens. The entire process complies with ICH Q11 guidelines for API development, employing temperature-gradient reaction technology to achieve intermediate purification rates exceeding 98%. Critical process parameters (CPPs) have been comprehensively validated to ensure process stability and reproducibility.
Quality Control
Quality control of amlodipine besylate API strictly follows the Chinese Pharmacopoeia 2025 Edition, Vol. II, and relevant international pharmacopoeias (USP, EP). The quality control system encompasses full-process monitoring from starting materials and intermediates to finished product. Key quality control indicators are as follows:
| Test Item | Specification | Method |
|---|---|---|
| Appearance | White or off-white crystalline powder | Visual inspection |
| Identification | UV absorption & IR spectrum consistent with reference standard | UV / IR |
| Assay | 98.0%–102.0% (calculated on anhydrous basis) | HPLC |
| Related Substances | Total impurities ≤ 1.0%, any single impurity ≤ 0.3% | HPLC |
| Water Content | ≤ 0.5% | Karl Fischer titration |
| Residue on Ignition | ≤ 0.1% | Residue on ignition test |
| Heavy Metals | ≤ 10 ppm | Atomic Absorption / ICP-MS |
| Residual Solvents | Compliant with ICH Q3C limits | GC |
| Crystal Form | Consistent with RLD | XRPD / DSC |
| Particle Size Distribution | D90 within specified range | Laser diffraction |
System suitability requirements: The retention time of the amlodipine peak in the chromatogram is approximately 18 minutes. The resolution between the amlodipine peak and the amlodipine impurity I peak (relative retention time ~0.5) must exceed 4.5; theoretical plates calculated from the amlodipine peak must be at least 3,000. Impurity profiling covers both process-related and degradation impurities, with a comprehensive impurity profile database established to ensure product quality consistent with the originator product.
Patent Landscape
The core compound patent for amlodipine besylate (US 4,572,866) expired in 2007, substantially eliminating compound patent barriers and providing a favorable window for generic drug development. However, attention must be paid to the following process- and crystal form-related patents, which should be circumvented during process design:
| Publication No. | Type | Filing Date | Title | Applicant | Legal Status |
|---|---|---|---|---|---|
| CN101367759 | Preparation | 2008.09 | High-Purity Synthesis of Amlodipine Besylate | Related Company | Granted |
| CN108456160A | Preparation | 2018.02 | Synthesis Process for Amlodipine Besylate | Related Company | Granted |
| US6784297B2 | Preparation | 2002.09 | Preparation of Amlodipine Besylate (Anti-ischemic & Antihypertensive) | Pfizer | Expired |
| CN110944979B | Crystal Form/Prep. | 2017.08 | Crystal Form of Amlodipine Besylate and Preparation Thereof | Related Company | Granted |
Comprehensive patent searching and FTO (Freedom to Operate) analysis have been conducted during the process route design phase of this project. The selected synthetic route and crystal form fall outside the protection scope of the above active patents, ensuring that product commercialization will be free of intellectual property risks. Detailed patent analysis reports are available upon request from our technical team.
Product Advantages
- Established Clinical Position: Amlodipine besylate is one of the most prescribed antihypertensive drugs globally, supported by multiple large-scale evidence-based studies including ALLHAT, ASCOT, VALUE, and CAMELOT. It has demonstrated robust evidence in reducing cardiovascular events such as stroke and myocardial infarction, and is recommended as a first-line antihypertensive agent by multiple domestic and international hypertension management guidelines.
- Favorable Pharmacokinetic Profile: With an elimination half-life of 35–50 hours, once-daily dosing achieves 24-hour stable blood pressure reduction, with peak-to-trough ratio approaching unity and high patient compliance. Oral bioavailability reaches 64–90% and is not affected by food intake.
- Excellent Safety Record: Does not affect sinus node or atrioventricular conduction function; does not increase cardiovascular morbidity or mortality in heart failure patients (PRAISE study); demonstrates favorable safety in elderly patients and those with hepatic or renal impairment; minimal drug-drug interactions.
- Large Market Volume: As a National Essential Drug and NRDL-listed product, demand continues to grow under the backdrop of normalized volume-based procurement (VBP), offering broad market opportunities for the API sector.
- Mature and Controllable Process: This project employs an optimized two-stage Hantzsch reaction route with stable process performance, yield exceeding 45%, well-controlled critical impurities, and competitive cost—well-suited for large-scale manufacturing.
Market Overview
Amlodipine besylate is one of the best-selling antihypertensive agents globally with an enormous market size. In the domestic China market, the amlodipine besylate tablet market reached approximately USD 1.13 billion in 2024, while the out-of-hospital market (urban retail pharmacies) exceeded RMB 2 billion in sales, representing 2.68% year-on-year growth. In 2022, national sales of this product reached RMB 5.5 billion, consistently ranking among the top antihypertensive products.
From a global perspective, according to QYResearch statistics and projections, the global amlodipine besylate capsule market reached USD 200 million in 2024 and is projected to reach USD 265 million by 2031, with a CAGR of 4.2% during 2025–2031. The Chinese market has maintained steady growth in recent years.
As China's population aging accelerates, the hypertensive patient population continues to expand. According to the National Center for Cardiovascular Diseases, China has over 245 million hypertensive patients. The national promotion of tiered diagnosis and treatment has made primary-level hospitals key sites for chronic disease management, driving demand growth for this product in county-level and below markets. Furthermore, the national Volume-Based Procurement (VBP) policy has accelerated the substitution of originator drugs with generics, continuously increasing API demand and creating broad market opportunities for enterprises with large-scale manufacturing capabilities.
Project Progress
- Small-scale process research has been completed, establishing a stable and reproducible synthetic route with an overall yield consistently above 45%.
- Quality standards for starting materials and key intermediates have been established; comprehensive impurity profiling has been completed.
- Finished product quality studies have been completed; all specifications comply with the requirements of the Chinese Pharmacopoeia 2025 Edition, Vol. II.
- Pilot-scale-up research and process validation are currently underway.
For detailed technical documentation and process parameters of this project, please contact our technical team for further discussion. Taikomed has extensive technical expertise and industrialization experience in API process development, and provides one-stop technical services spanning from process development to regulatory filing.