Sodium starch glycolate (SSG) is a modified starch used in tablets and capsules to make them break apart quickly after you swallow them. It’s one of the most common inactive ingredients in pharmaceutical products, appearing on the label of countless over-the-counter and prescription medications. Its sole job is to ensure the tablet doesn’t pass through your digestive system intact, so the actual drug inside can dissolve and get to work.
How It Works Inside a Tablet
SSG is what pharmacists call a “superdisintegrant.” When a tablet reaches your stomach and contacts fluid, SSG particles absorb water rapidly and swell. That swelling creates internal pressure inside the compressed tablet, and once that pressure overcomes the forces holding the tablet together, the tablet breaks apart into smaller pieces. Those smaller pieces expose more surface area to your stomach fluid, which lets the active drug dissolve faster.
The degree of chemical cross-linking in SSG determines whether it swells or turns into a gel. Properly cross-linked SSG swells powerfully without dissolving, which is what you want. If the cross-linking is too low, SSG forms a sticky gel layer instead, which actually slows things down by blocking water from penetrating deeper into the tablet.
How Much Goes Into a Tablet
Most tablets contain between 2% and 8% SSG by weight. That concentration range matters more than you might expect. In paracetamol (acetaminophen) tablets, using just 1% SSG resulted in disintegration times as long as 15 minutes, while tablets with 2% or 4% SSG broke apart consistently within one minute. Go above 8%, though, and the effect reverses. Too much SSG creates a viscous barrier that prevents water from reaching the tablet’s core, actually increasing the time it takes to disintegrate.
This sweet spot between 2% and 8% applies across most drug formulations, regardless of whether the active ingredient dissolves easily in water or not.
What It’s Made From
SSG is made by chemically modifying natural starch, typically from potato or wheat sources. The starch is treated to add carboxymethyl groups and then cross-linked, which gives it that powerful water-absorbing behavior. There are two pharmaceutical grades. Type A has a pH between 5.5 and 7.5 and a sodium content of 2.8% to 4.2%. Type B is more acidic, with a pH between 3.0 and 5.0 and a lower sodium content of 2.0% to 3.4%. The grade a manufacturer chooses depends on the specific drug formulation and its stability requirements.
The Gluten Question
If you have celiac disease or gluten sensitivity, SSG is worth paying attention to. When derived from wheat starch, it could theoretically contain trace amounts of gluten. The FDA has noted that wheat-derived SSG might contain gluten at concentrations of 100 to 500 mg per kilogram of the ingredient. However, because so little SSG goes into each tablet, the FDA estimates that it contributes less than 0.5 mg of gluten per dose of any oral medication.
For most people with celiac disease who respond well to a gluten-free diet, the FDA considers this level low-risk. That said, people with unusually high gluten sensitivity, particularly those who don’t respond well to a standard gluten-free diet, may want to check whether their medications use wheat-derived SSG. Potato-derived versions are available and contain no gluten. Your pharmacist can often help identify the source.
How It Compares to Other Disintegrants
SSG is one of three synthetic superdisintegrants commonly used in tablets. The other two are croscarmellose sodium (made from modified cellulose) and crospovidone (a synthetic polymer). All three produce tablets with acceptable hardness, consistent disintegration, and reliable drug release. The choice between them often comes down to compatibility with the active drug, the manufacturing process being used, and how the tablet needs to behave in the body.
SSG primarily works through swelling, while crospovidone relies more on wicking water into the tablet through capillary action. Croscarmellose sodium uses a combination of both mechanisms. Each has trade-offs depending on the specific formulation.
Stability and Drug Compatibility
SSG absorbs moisture from the environment, which is useful for tablet disintegration but can cause problems during storage. The water that accumulates on SSG particle surfaces can trigger chemical reactions with certain drugs. One well-documented example involves enalapril maleate, a blood pressure medication. When mixed with SSG, the moisture layer on the SSG surface causes enalapril to lose its crystalline structure and break down into an inactive compound. The effect worsens as the proportion of SSG increases and as ambient moisture rises.
This is why pharmaceutical manufacturers run extensive compatibility testing before choosing SSG for a given formulation. For the end user, it’s also a good reason to store medications in a cool, dry place with the cap tightly sealed, especially in humid climates.
Safety Profile
SSG has a long track record of safe use in pharmaceuticals. It’s classified as an inactive ingredient by the FDA, and the amounts used in tablets are far too small to have any pharmacological effect on your body. When the EPA evaluated it for use in pesticide tablet formulations, they established an exemption from tolerance limits, meaning no maximum residue level was considered necessary. The only restriction was that it shouldn’t exceed 8% of the product by weight, which aligns with the pharmaceutical convention of keeping concentrations at or below 8% for performance reasons, not safety ones.
Because SSG passes through the digestive tract without being absorbed in meaningful amounts, it doesn’t interact with your body’s chemistry. It simply does its job of breaking the tablet apart, then moves through your system along with the other inactive ingredients.