Deoxycholic Acid

Deoxycholic acid is one of the secondary bile acids, formed when intestinal bacteria remove a hydroxyl group from cholic acid, a primary bile acid that the liver secretes into bile ^[1]. It is a steroid-based acid, appearing as a white crystalline solid in pure form, and it circulates in bile alongside the other bile acids.

As a natural detergent, deoxycholic acid helps emulsify fats in the intestine so that they can be broken down and absorbed. That same surfactant property makes its sodium salt, sodium deoxycholate, a common laboratory reagent for lysing cells and dissolving cellular and membrane components.

A purified, synthetic version of the acid, developed as ATX-101 and marketed as Kybella and Belkyra, is injected to reduce moderate-to-severe fat below the chin, the so-called double chin ^[1][2]. Approved in 2015, it was the first drug approved for this purpose; several large phase III trials enrolling more than a thousand patients demonstrated measurable reduction of submental fat using validated clinical scales and imaging ^[1].

When injected into the subcutaneous fat, deoxycholic acid physically disrupts the membranes of fat cells, causing them to break apart in a process called adipocytolysis and setting off a local inflammatory response in which macrophages clear the debris and the tissue partly fibroses ^[3]. Because this healing takes time, the reduction in fat is gradual and usually requires several monthly treatment sessions ^[3][4]. Injection-site reactions such as swelling, bruising, numbness, and pain are very common but transient ^[1][4].

In the intestine, high levels of deoxycholate have also been studied in connection with colon cancer risk, and its concentrations can be shifted by diet. As a medicine it is a prescription injectable administered by trained clinicians, and it is separately available as a laboratory chemical in the form of sodium deoxycholate.

This is a prescription injectable given by a clinician. Expected reactions at the injection site include swelling, bruising, pain, numbness, firmness, and redness, and these usually fade over days to weeks. The most important serious risk is nerve injury: hitting the marginal mandibular nerve can cause a temporary lopsided smile, and injecting too deeply can damage swallowing. Because of this, it must be placed only in the fat under the chin by someone who knows the anatomy, avoiding areas near major nerves and vessels. It is not meant for fat elsewhere on the body outside of studied uses, and injection into or near infection or into muscle should be avoided.

Deoxycholic acid is a naturally occurring secondary bile acid that has been known to physiology and biochemistry for well over a century, long used in the laboratory as a detergent for solubilizing membranes. Its modern medical career began when the biotechnology company Kythera Biopharmaceuticals developed a purified, synthetic injectable formulation, designated ATX-101, specifically to dissolve unwanted fat.

After a program of clinical trials demonstrating its ability to reduce moderate submental fullness, the drug was approved by the United States Food and Drug Administration in 2015 and marketed as Kybella, with the name Belkyra used in other markets. Allergan subsequently acquired Kythera and the product, cementing deoxycholic acid's place as the first injectable approved for reducing fat beneath the chin. Its introduction offered a nonsurgical alternative to liposurgery for a common cosmetic concern and helped define the category of injectable adipocytolytics.

Deoxycholic acid is well regarded as a convenient, minimally invasive option for reducing a modest double chin without surgery, and it is appreciated for producing results that appear durable once the treated fat cells are cleared. Aesthetic practitioners value the predictability of the outcome when injections are performed with careful attention to anatomy. Patients are typically advised that transient swelling, bruising, and numbness are common after treatment, and that several sessions may be needed. Because the molecule is a nonselective detergent, precise placement is emphasized to avoid injury to nearby nerves, a point reinforced by experimental studies of off-target effects. Overall it is seen as an effective and honestly bounded tool best suited to the specific problem it was designed to address.