| UDCA CAS | 128-13-2 |
|---|---|
| CDCA CAS | 474-25-9 |
| Classification | Both Secondary Bile Acids |
| UDCA Origin | 7-epimerization of CDCA |
| CDCA Origin | Primary bile acid (liver synthesis) |
| UDCA FDA Approved | PBC, gallstone dissolution |
| CDCA FDA Approved | Gallstone dissolution (historical) |
| UDCA Pharmacopoeias | USP, EP, BP, JP, ChP |
| CDCA Pharmacopoeias | EP, BP, JP |
| UDCA Global Production | 600+ MT/year |
| CDCA Global Production | 100-150 MT/year |
Ursodeoxycholic acid (UDCA) and chenodeoxycholic acid (CDCA) are the two most clinically significant bile acid APIs in the pharmaceutical supply chain. They share a biosynthetic pathway but differ substantially in safety profile, regulatory status, and commercial availability. For procurement professionals evaluating which bile acid to source, understanding these distinctions is essential to making an informed supplier decision.
UDCA and CDCA are stereoisomers with the same molecular formula (C24H40O4) and molecular weight (392.57 g/mol). The single structural difference that defines their distinct biological properties is the orientation of the hydroxyl group at the 7-position of the steroid nucleus. This seemingly minor change produces profound differences in hydrophilicity, cytotoxicity, and therapeutic effect.
CDCA has a 7-alpha hydroxyl group, giving it a hydrophobic character. In the physiological bile acid pool, CDCA is one of the two primary bile acids synthesized directly from cholesterol in hepatocytes, along with cholic acid. Its hydrophobicity makes it a potent detergent for dietary fat emulsification, but this same property also enables it to disrupt cell membranes at elevated concentrations, contributing to its hepatotoxic potential at therapeutic doses.
UDCA, by contrast, has a 7-beta hydroxyl group (the epimer of CDCA at C-7). This change reorients the hydroxyl group from the alpha (below the plane) to the beta (above the plane) configuration, substantially increasing the molecule's hydrophilicity. UDCA is approximately 100-fold less cytotoxic to hepatocytes than CDCA in vitro, as demonstrated by Heuman et al. (1991, Gastroenterology). The beta configuration also alters how UDCA interacts with bile acid transporters and nuclear receptors, including FXR (farnesoid X receptor) and TGR5, which underpin its therapeutic mechanism of action.
CDCA is a primary bile acid naturally synthesized in the human liver from cholesterol via the classic (CYP7A1-mediated) pathway. It is present in human bile at concentrations of 20-30% of the total bile acid pool. Historically, pharmaceutical CDCA was isolated from animal bile sources, but modern production relies on semi-synthetic or fully synthetic routes starting from cholic acid or other steroid precursors derived from the bovine bile supply chain.
UDCA is a secondary bile acid produced naturally in small quantities (approximately 1-5% of the human bile acid pool) through 7-epimerization of CDCA by intestinal bacteria, primarily Clostridium and Ruminococcus species. Industrial-scale UDCA production uses chemical 7-epimerization of CDCA as the key synthetic step. This means that CDCA is not only a therapeutic agent in its own right but also the essential precursor for UDCA manufacturing. The availability and cost of CDCA directly influence UDCA production economics, which is a critical factor for procurement teams to understand when analyzing bile acid API sourcing from China.
While UDCA and CDCA both interact with the enterohepatic circulation of bile acids, their mechanisms of action diverge notably at the molecular level, leading to different therapeutic profiles and clinical applications.
Both UDCA and CDCA dissolve cholesterol gallstones by reducing hepatic cholesterol secretion and decreasing biliary cholesterol saturation. CDCA achieves this primarily through suppression of HMG-CoA reductase (the rate-limiting enzyme in cholesterol synthesis) and reduction of intestinal cholesterol absorption. UDCA works through a distinct mechanism: it reduces the intestinal absorption of cholesterol, decreases hepatic cholesterol secretion into bile, and promotes the formation of a liquid crystalline phase that extracts cholesterol from the surface of existing gallstones.
The key clinical difference is that UDCA achieves gallstone dissolution at lower doses (8-10 mg/kg/day) with substantially fewer side effects compared with CDCA (12-15 mg/kg/day). UDCA also induces the formation of a cholesterol-rich liquid crystalline phase at the gallstone surface, whereas CDCA acts primarily through micellar solubilization. This translates to better patient tolerability and higher treatment completion rates with UDCA, which is why CDCA has been almost entirely replaced by UDCA for this indication in modern clinical practice.
UDCA's hepatoprotective effects are well-documented and stem from multiple complementary mechanisms: (1) displacement of toxic endogenous hydrophobic bile acids from the bile acid pool and from hepatocyte membranes, (2) stimulation of hepatobiliary secretion through post-transcriptional regulation of transporter expression, (3) inhibition of hepatocyte apoptosis via stabilization of the mitochondrial membrane and reduction of Bax translocation, and (4) immunomodulatory effects including reduction of aberrant MHC class I expression on hepatocytes. These mechanisms are particularly relevant in cholestatic liver diseases such as primary biliary cholangitis (PBC).
CDCA lacks these hepatoprotective effects entirely. On the contrary, CDCA at therapeutic concentrations can be hepatotoxic, as evidenced by dose-dependent elevations in serum transaminases observed in clinical trials. This is one of the primary reasons CDCA was superseded by UDCA for chronic liver disease indications. The hepatotoxicity risk of CDCA is dose-related and is thought to result from its hydrophobic nature and its detergent effect disrupting hepatocyte and cholangiocyte membranes, particularly in patients with compromised hepatic function.
Oral administration of UDCA at 13-15 mg/kg/day enriches the circulating bile acid pool to approximately 40-60% UDCA content (from a baseline of 1-5%), displacing the more hydrophobic and cytotoxic endogenous bile acids such as CDCA, deoxycholic acid, and lithocholic acid. This enrichment is the cornerstone of UDCA's therapeutic effect in cholestatic conditions.
CDCA administration enriches the bile acid pool with CDCA, which can reach 80-90% of the total pool at therapeutic doses. However, since CDCA is itself a hydrophobic, potentially cytotoxic bile acid, this enrichment does not confer the same protective effect as UDCA enrichment. CDCA's effect on the bile acid pool is primarily a quantitative expansion of the primary bile acid fraction, which explains its efficacy in gallstone dissolution but also its adverse effect profile.
The clinical adoption of UDCA and CDCA has diverged substantially since the 1980s. Understanding the indication-specific data is essential for procurement teams aligning API sourcing with target formulations.
CDCA was the first bile acid approved by the FDA for cholesterol gallstone dissolution, receiving approval in 1980. Early clinical trials demonstrated that CDCA at 12-15 mg/kg/day achieved partial or complete gallstone dissolution in 40-60% of patients with radiolucent gallstones smaller than 15 mm. However, CDCA treatment was associated with dose-dependent diarrhea in 30-50% of patients and mild-to-moderate transaminase elevations in approximately 25% of patients, limiting its clinical utility. The UDCA gallstone dissolution data from the National Cooperative Gallstone Study and subsequent trials showed comparable or superior efficacy at 8-10 mg/kg/day, with diarrhea rates below 5% and no significant hepatotoxicity. For further detail on UDCA's gallstone dissolution applications, see UDCA and Gallstone Dissolution.
UDCA's superior tolerability profile led to its replacement of CDCA as the first-line oral dissolution agent for cholesterol gallstones by the early 1990s. CDCA is now rarely prescribed for this indication, though it remains available in some markets. From a procurement perspective, the global demand for CDCA as a finished drug product API for gallstone treatment is negligible compared with its role as a UDCA synthesis intermediate.
UDCA is the only FDA-approved drug for primary biliary cholangitis (PBC) and is recommended as first-line therapy by the AASLD and EASL clinical practice guidelines. The pivotal evidence comes from combined analysis of three large randomized controlled trials (Poupon et al., 1997, Gastroenterology) involving 548 patients, which demonstrated that UDCA at 13-15 mg/kg/day notably prolonged transplant-free survival in patients with moderate-to-severe PBC. More recent real-world data from the Global PBC Study Group (n=3,902) confirmed that UDCA-responders have survival rates comparable to the age- and sex-matched general population. For a comprehensive review of UDCA's liver disease applications, see UDCA Liver Disease Treatment.
CDCA has no role in PBC treatment. Early investigations of CDCA in PBC were discontinued due to hepatotoxicity. This contrasts sharply with UDCA, which is listed in the WHO Model List of Essential Medicines specifically for PBC. The prescription volume for UDCA in PBC represents the single largest indication by value in the global UDCA market, and procurement teams targeting this indication should ensure their UDCA API supplier holds the relevant DMF and CEP filings for regulated markets.
Beyond gallstone dissolution and PBC, UDCA is investigated or used off-label in several additional indications: primary sclerosing cholangitis (PSC), intrahepatic cholestasis of pregnancy (ICP), cystic fibrosis-associated liver disease, non-alcoholic steatohepatitis (NASH), and as a chemo-preventive agent for colorectal cancer in patients with PSC and ulcerative colitis. CDCA, conversely, has found a niche application in cerebrotendinous xanthomatosis (CTX), a rare inborn error of bile acid synthesis, through the CDCA product Chenodal (approved by the FDA as an orphan drug). CDCA is also under investigation as part of combination therapies (with obeticholic acid or fibrates) but is not a standalone first-line agent for any common hepatobiliary indication.
The side effect profiles of UDCA and CDCA represent the most clinically meaningful differentiator between these two bile acid APIs. The tolerability gap is well-documented in head-to-head clinical trials and directly influences which API a formulator selects for a given drug product.
Diarrhea is the dose-limiting toxicity of CDCA and the principal reason for its therapeutic abandonment. CDCA-induced diarrhea is secretory in nature, resulting from CDCA's stimulation of colonic chloride and water secretion. At the therapeutic dose of 12-15 mg/kg/day, diarrhea occurs in 30-50% of patients, with approximately 10-15% experiencing severe diarrhea requiring dose reduction or treatment discontinuation. The mechanism is well-characterized: CDCA activates colonic epithelial cell cyclic AMP-dependent chloride channels, leading to net fluid secretion into the colonic lumen.
UDCA, by contrast, causes diarrhea in fewer than 5% of patients at standard therapeutic doses. When UDCA-related diarrhea does occur, it is generally mild and self-limiting. This tolerability advantage is a direct consequence of UDCA's greater hydrophilicity and reduced membrane-disrupting potential compared with CDCA. Data from clinical trials consistently show that treatment completion rates are notably higher with UDCA (85-95%) than with CDCA (50-70%).
CDCA causes dose-dependent elevations in serum transaminases (AST, ALT) in approximately 25-30% of patients, with approximately 5-10% of patients developing elevations exceeding three times the upper limit of normal. These transaminase elevations are typically asymptomatic and reversible upon dose reduction or discontinuation, but they represent a meaningful safety signal that limits CDCA's suitability for chronic administration, particularly in patients with pre-existing liver disease.
UDCA does not cause hepatotoxicity at any therapeutic dose. On the contrary, UDCA reduces serum transaminase levels in patients with cholestatic liver disease, an effect that forms part of the biochemical response criteria used to assess treatment efficacy in PBC. The mechanism of UDCA's hepatoprotection (discussed in Section 2.2) explains the absence of hepatotoxicity, and long-term safety data of over 10 years of continuous UDCA use have not revealed hepatic safety signals.
UDCA has an extensive long-term safety record with over 30 years of post-marketing surveillance data. The UDCA safety database includes data from the Global PBC Study Group (median follow-up of 7.8 years, n=3,902) and multiple 10-year extension studies. No late-emerging safety signals were identified. CDCA's long-term safety data are more limited. The Chenodal (CDCA) prescribing information carries a warning regarding hepatotoxicity, and CDCA is contraindicated in patients with known liver disease aside from the specific conditions for which it is indicated.
For a detailed discussion of UDCA's safety profile, see UDCA Side Effects and Safety Profile. For CDCA, the safety documentation is considerably less comprehensive, reflecting its secondary status in the global pharmaceutical market.
Pharmacopoeia coverage is a critical consideration for pharmaceutical procurement. A monograph in a recognized pharmacopoeia defines the quality standard that the API must meet and provides a common reference for buyer-supplier quality agreements.
| Parameter | UDCA | CDCA |
|---|---|---|
| USP Monograph | Yes (Ursodiol) | No (withdrawn) |
| EP Monograph | Yes (monograph 1275) | Yes (monograph 1189) |
| BP Monograph | Yes | Yes |
| JP Monograph | Yes | Yes |
| ChP Monograph | Yes | Yes |
| Assay Specification (EP) | 99.0-101.0% (dried substance) | 98.0-102.0% (dried substance) |
| Related Substances (EP) | CDCA ≤ 0.10%; LCA ≤ 0.15%; total ≤ 0.5% | UDCA ≤ 0.15%; LCA ≤ 0.15%; total ≤ 0.5% |
| Specific Rotation (EP) | +58.0 to +62.0 (anhydrous) | +11.0 to +13.0 (anhydrous) |
| Residual Solvents | ICH Q3C (ethanol ≤ 5000 ppm typical) | ICH Q3C (varies by route) |
| DMF Filing (FDA) | Active Type II DMFs from multiple Chinese manufacturers | Limited DMFs; fewer manufacturers |
| CEP (EDQM) | Active CEPs from 5+ Chinese manufacturers | Limited CEPs; 1-2 Chinese manufacturers |
Data compiled from USP-NF, EP 11, BP 2024, JP 18, and ChP 2020 monographs; DMF/CEP data from FDA and EDQM public databases as of Q2 2026.
The critical difference for procurement is that UDCA has a USP monograph, while CDCA does not (the USP CDCA monograph was withdrawn). For pharmaceutical manufacturers targeting the US market, the absence of a USP monograph for CDCA means that an alternative quality standard (typically EP) must be referenced in the ANDA or NDA filing, which adds a layer of regulatory complexity. UDCA's presence in all major pharmacopoeias makes it the more straightforward choice for global regulatory submissions.
UDCA and CDCA occupy different positions in the global bile acid API supply chain, and these differences have practical implications for procurement strategy.
UDCA is widely available from Chinese manufacturers, with 15+ GMP-certified production sites located primarily in Shandong, Jiangsu, Zhejiang, and Tianjin provinces. Global UDCA production capacity exceeds 600 metric tons annually. The mature supplier base means competition is healthy and alternatives exist if a primary supplier faces quality or delivery issues. CDCA, by contrast, has approximately 5-10 GMP-certified producers globally, with a smaller Chinese manufacturing base. CDCA availability is also indirectly tied to UDCA production demand, since CDCA is the key intermediate for UDCA synthesis.
CDCA is generally less expensive per kilogram than UDCA on the merchant market, reflecting its role as an intermediate rather than a finished drug product API. However, the price differential narrows for pharmaceutical-grade CDCA meeting EP monograph specifications, particularly for smaller order volumes where the fixed costs of GMP documentation and regulatory compliance are amortized over fewer kilograms. UDCA pricing is more transparent and competitive due to the larger number of suppliers and higher market volumes. For the most accurate pricing on either API, contact KingWish for current FOB and CIF quotations based on your specific quality grade and volume requirements.
UDCA quality tiers are well-defined: EP/USP-grade (pharmaceutical), feed/food-grade, and cosmetic-grade. The majority of traded volumes are pharmaceutical grade. CDCA quality tiers are less standardized: EP-grade for pharmaceutical use, industrial-grade for UDCA synthesis intermediate, and research-grade for laboratory applications. Because CDCA frequently is a UDCA precursor, the quality specification for industrial-grade CDCA may differ from EP-grade CDCA, and procurement teams should confirm which specification applies before ordering.
The decision between sourcing UDCA and CDCA depends on the intended application, target market, and regulatory pathway. The table below outlines the primary scenarios.
| Use Case | Recommended API | Reasoning |
|---|---|---|
| Pharmaceutical finished product (gallstone dissolution) | UDCA | Superior safety profile; first-line therapy; USP/EP monographs; broad regulatory acceptance |
| Pharmaceutical finished product (PBC treatment) | UDCA | Only FDA-approved bile acid for PBC; WHO Essential Medicine; extensive clinical evidence |
| UDCA synthesis (in-house) | CDCA | CDCA is the direct precursor for UDCA production via 7-epimerization |
| Cerebrotendinous xanthomatosis (CTX) | CDCA | CDCA is the FDA-approved orphan drug for CTX; UDCA is not effective for this indication |
| US market ANDA filing | UDCA | USP monograph available; multiple active DMFs; established regulatory pathway |
| EU market MAA filing | UDCA (preferred) or CDCA | Both have EP monographs and CEP availability, but UDCA has more CEP holders |
| Dietary supplement formulation | UDCA | Wider supplier base; better pricing; recognized as supplement ingredient in certain markets |
| Combined API procurement (dual-source simplification) | Both from one partner | Consolidate documentation, logistics, and quality management with a single supplier |
In the majority of pharmaceutical procurement scenarios, UDCA is the preferred bile acid API. CDCA remains relevant primarily as a UDCA synthesis intermediate and for the niche CTX indication.
China is the dominant origin for both UDCA and CDCA APIs in the global pharmaceutical supply chain. The country's integrated bile acid supply chain (from bovine bile extraction through to finished API) creates structural cost advantages that competitors in India, Europe, and North America cannot match at scale.
China hosts the world's largest concentration of UDCA API manufacturers, with over 15 GMP-certified producers operating in Shandong, Jiangsu, Zhejiang, and Tianjin provinces. Key factors in evaluating Chinese UDCA suppliers include: (1) GMP certification status (China NMPA GMP minimum; ideally EU GMP or ICH Q7 compliance), (2) FDA DMF filing status (active Type II DMF with recent FDA review cycle completion), (3) EDQM CEP validity, (4) production capacity and batch size consistency, and (5) quality system maturity as evidenced by inspection history from foreign regulatory authorities. The china udca api manufacturer comparison should include review of these five dimensions, not price alone. How to Source UDCA from China provides a detailed supplier evaluation framework.
The UDCA supplier landscape in China is mature and competitive. The largest Chinese producers operate dedicated UDCA production lines with annual capacities exceeding 40 metric tons. KingWish, as China's largest UDCA supplier by volume (40+ MT/year), maintains active DMF and CEP filings and serves pharmaceutical buyers in over 100 countries. For a complete overview of UDCA specifications, indications, and quality standards, see the UDCA Complete Guide and Ursodeoxycholic Acid product page.
China CDCA API supplier availability is more limited than UDCA. The CDCA manufacturing base in China is smaller, with an estimated 5-8 producers of pharmaceutical-grade CDCA meeting EP monograph standards. CDCA production in China is closely linked to UDCA production, since CDCA is the chemical precursor for UDCA synthesis. Many UDCA manufacturers produce CDCA in-house as an intermediate rather than purchasing it on the merchant market. This structural integration means that standalone CDCA suppliers are relatively few.
For pharmaceutical buyers seeking a china cdca api supplier, the evaluation criteria are similar to UDCA: GMP certification, DMF/CEP availability, and quality system maturity. However, buyers should recognize that the CDCA supplier pool is smaller and documentation may be less comprehensive than for UDCA. When sourcing CDCA from China, verifying the synthetic route (to confirm it meets the specification grade required) and the supplier's ability to provide EP-compliant documentation are particularly important.
For pharmaceutical buyers requiring both UDCA and CDCA APIs (for example, manufacturers producing UDCA formulations while also developing CDCA-based products or procuring CDCA as a UDCA synthesis intermediate), there is a practical advantage to sourcing both bile acids from a single qualified Chinese partner. Combined sourcing from one supplier simplifies: (1) supplier qualification and audit management (one quality agreement instead of two), (2) documentation handling (consolidated DMF/CEP/CoA package), (3) logistics (combined shipments reduce freight costs and customs clearance complexity), and (4) commercial terms (volume consolidation may improve pricing and payment terms).
When evaluating a bile acid api China sourcing partner, inquire specifically about the supplier's ability to provide both UDCA and CDCA to the required pharmacopoeia grade, whether the CDCA is produced in-house or sourced from a qualified subcontractor, and whether combined orders can be shipped together. For guidance on navigating the broader landscape of bile acid options including TUDCA, see the full bile acid comparison guide.