Gavilyte and GoLYTELY are essentially the same medication. Both contain polyethylene glycol 3350 mixed with electrolytes, and both are used to clean out the bowel before a colonoscopy. The key difference is that GoLYTELY is the original brand-name product, while Gavilyte is a generic version. If your doctor or pharmacy swaps one for the other, you’re getting the same active formula.
Brand Name vs. Generic
GoLYTELY is the brand-name bowel prep that has been on the market for decades. Gavilyte, manufactured by Novel Laboratories for Lupin Pharmaceuticals, was approved through the FDA’s Abbreviated New Drug Application (ANDA) process. That process requires the generic to prove it contains the same active ingredients in the same amounts and works the same way in the body. In practical terms, your pharmacy may fill a GoLYTELY prescription with Gavilyte depending on what’s in stock or what your insurance prefers.
What’s Inside Both Products
When mixed with water to make a full gallon (about 4 liters), GoLYTELY contains polyethylene glycol 3350 at 60 grams per liter, along with sodium sulfate, sodium bicarbonate, sodium chloride, and potassium chloride. Gavilyte uses the same combination at the same concentrations. The polyethylene glycol pulls water into your intestines to flush them out, while the electrolytes help maintain your body’s salt and mineral balance so you don’t get dehydrated or thrown off chemically during the process.
You may see slightly different letter suffixes on Gavilyte products (Gavilyte-C, Gavilyte-G, Gavilyte-N). These correspond to minor formulation differences in the electrolyte salts or included flavor packs, and they each match a specific version of the brand-name prep.
Flavor and Taste
Neither product tastes good on its own. GoLYTELY kits typically come with an optional pineapple flavor packet you can mix in. Gavilyte versions often include their own flavor packs as well, sometimes in different flavor options like lemon or cherry depending on the specific product. Adding the flavor pack doesn’t change the color of the solution, which should remain clear. Many people find that chilling the mixed solution and drinking it through a straw makes the large volume more tolerable regardless of which brand they’re using.
How the Prep Works
The prep experience is identical for both products. You’ll mix the powder with lukewarm water up to the fill line on the jug (about 4 liters total), shake it until dissolved, then refrigerate it. Most doctors now recommend a split-dose approach: you drink half the jug the evening before your colonoscopy, typically over a two-hour window, and the second half the morning of the procedure about four hours before you need to leave for your appointment. Each half is roughly 64 ounces.
Expect frequent, watery bowel movements to start within an hour or so of your first glass. The goal is for your stool to become clear or light yellow, which tells you (and your doctor) that the colon is clean enough for a good exam. PEG-based preps like these achieve a good or excellent bowel cleansing about 89 to 93 percent of the time, which is on par with other common prep options.
Side Effects Are the Same
Because the formula is identical, the side effects are too. The most common complaints are nausea, bloating, and abdominal cramping, all caused by drinking a large volume of salty liquid in a short window. Some people experience vomiting, especially if they try to drink too quickly. Slowing your pace to about 8 ounces every 10 to 15 minutes usually helps. The electrolyte balance in the solution is designed to prevent the dangerous fluid shifts that plain water or other laxatives could cause, which is why doctors still prescribe these large-volume preps for patients with kidney problems or heart conditions.
Cost Differences
As a generic, Gavilyte is often less expensive than GoLYTELY at the pharmacy counter, though exact pricing depends on your insurance plan and pharmacy. Without insurance, a 4-liter jug of PEG-electrolyte prep runs roughly $30. Many insurance plans and pharmacy benefit managers will automatically substitute the generic to save you money. If your prescription specifically says GoLYTELY and you’re being charged more, ask your pharmacist whether the generic version is available at a lower copay.
Does It Matter Which One You Get?
Not in any meaningful clinical way. The active ingredients, the volume you drink, the timeline, the effectiveness, and the side effects are all the same. The only differences are the manufacturer’s name on the label, the specific flavor pack included, and potentially the price. If your doctor writes a prescription for one and the pharmacy gives you the other, you can use it with confidence that your colonoscopy prep will work exactly as intended.