Glyceryl undecylenate in eye drops

Glyceryl undecylenate is one of the 10 inactive ingredients in Quell. Chemically, it’s an ester formed from glycerol and undecylenic acid, a fatty acid that the NIH’s PubChem database traces back to castor oil. On the label it’s listed with the other inactive ingredients rather than as an active, so no specific purpose or amount is stated for it. Here’s what the chemistry says and where it sits in the formula.

What glyceryl undecylenate is

PubChem, the chemistry database run by the National Library of Medicine at the NIH, lists the compound as glyceryl 1-undecylenate. Its record gives:

• Molecular formula: C14H26O4.
• IUPAC name: 2,3-dihydroxypropyl undec-10-enoate.
• PubChem compound ID: 9921382.

That IUPAC name can be read in two halves. “Undec-10-enoate” is the fatty acid part: eleven carbons with a double bond at the tenth position. “2,3-dihydroxypropyl” is what’s left of glycerol after one of its three hydroxyl groups has bonded to the acid. The other two hydroxyl groups are still free, which is why chemists call this a monoester, and why the “1” appears in glyceryl 1-undecylenate.

Where undecylenic acid comes from

The acid half has its own PubChem entry, under the IUPAC name undec-10-enoic acid, with the formula C11H20O2. According to PubChem, undecylenic acid was first isolated in 1877 from the products of distilling castor oil, through the breakdown of ricinoleic acid, the main fatty acid in castor oil. That’s the basis for the common description of glyceryl undecylenate as castor-derived.

PubChem’s record doesn’t say where any particular manufacturer sources its supply, and Quell’s label doesn’t either. What the label does is name the ingredient so you can look it up.

Reading the name on a label

Ingredient names on labels follow naming conventions that make them easier to decode once you know the pattern. “Glyceryl” at the front tells you glycerol is the backbone. The second word names the fatty acid, with “-ate” marking it as an ester rather than the free acid. So glyceryl undecylenate is undecylenic acid attached to glycerol, glyceryl laurate is lauric acid attached to glycerol, and so on.

You may also see slightly different names for it in different databases, such as PubChem’s glyceryl 1-undecylenate, where the number points to the glycerol carbon the acid is attached to. When you look up any label ingredient, matching the formula or the full chemical name is a more reliable check than matching the everyday name alone.

Where it appears on Quell’s label

Quell’s Drug Facts panel separates active ingredients, which carry a stated purpose, from inactive ingredients, which don’t. The active ingredients are Glycerol (1.0%), Polysorbate 80 (1.0%) and Light Mineral Oil (0.5%). The inactive list reads: Caprylyl Glycol, Dead Sea Salt (Sodium Chloride), Emu Oil, Glyceryl Laurate, Glyceryl Undecylenate, Manuka Honey, Polaxamer 188, Sterile Water, Terminalia Chubula and Tromethamine.

Inactive ingredients on an OTC drug label are listed by name only, without amounts. That’s normal and doesn’t mean an ingredient is unimportant to the formula; it means the label doesn’t make a claim for it. Our guide to the inactive ingredients section explains how that part of the panel works.

Glyceryl undecylenate and glyceryl laurate

Quell has two glyceryl esters in its inactive list, and they sit side by side. Glyceryl laurate pairs glycerol with lauric acid, a twelve-carbon saturated fatty acid. Glyceryl undecylenate pairs glycerol with an eleven-carbon acid that has one double bond near its tail. Same backbone, different fatty acid.

Molecules like these, with a water-friendly glycerol head and an oil-friendly fatty acid tail, are common in products that combine oily and watery ingredients. Quell contains both kinds, from light mineral oil and emu oil on one side to sterile water on the other. Our guide to glyceryl laurate and glyceryl undecylenate compares the pair, and what emulsion eye drops are covers why oil-and-water formulas look milky.

How it fits with the other inactives

• Caprylyl glycol: a small glycol-type molecule.
• Dead Sea salt (sodium chloride): a mineral salt.
• Emu oil, manuka honey and Terminalia chebula: the natural-origin ingredients the brand highlights.
• Glyceryl laurate and glyceryl undecylenate: the two glyceryl esters.
• Poloxamer 188 and tromethamine: formulation helpers common in eye products.
• Sterile water: the base the rest is carried in.

Our page on the natural ingredients in Quell goes into the plant- and animal-derived ingredients, and the Drug Facts page shows the full panel.

What this means when you use Quell

Knowing what an inactive ingredient is can help you, or your pharmacist, check a label against any sensitivities you have. It doesn’t change how to use the product. The label’s directions read: Apply 1 drop 3 times per day in each eye. Its warnings include: Caution should be used in those with egg or bird allergies — For use in the eyes only. The label also notes: The eye drops have a naturally milky-brown appearance. This is normal and does not indicate a problem with the product.

If you have a known sensitivity to castor-derived ingredients or to any item on the inactive list, show the list to your pharmacist or doctor before you start. The label also says: Stop use and ask a doctor if you feel eye pain or changes in your vision, if irritation or redness continues, or if the condition worsens or persists for 72 hours.