Quick answer: Colace is a brand name; docusate sodium is its active ingredient, and it is often compared against generic PEG 3350 (the ingredient in MiraLAX). For adults with chronic constipation, PEG 3350 is the better-supported choice based on available guideline evidence: the 2023 AGA/ACG clinical practice guideline gives it a strong recommendation based on moderate-certainty evidence.
The guideline did not provide an assessment or recommendation for docusate, because stool softeners and surfactant laxatives were not formally assessed; this reflects a lack of sufficient trial data rather than a finding that docusate does not work.[1,2]
Docusate is still used in some postoperative bowel regimens, particularly when minimizing straining is a clinical consideration, although evidence that it meaningfully improves constipation outcomes is limited.
PEG 3350 vs Colace for constipation is one of the most common comparisons people search for when standing in a pharmacy aisle comparing polyethylene glycol 3350 powder (PEG 3350) to docusate sodium capsules (the active ingredient behind Colace). You have probably noticed they are often marketed as similar, gentle, non-stimulant options for constipation.
Clinically, they are not similar at all. One is an osmotic laxative with a substantially stronger body of clinical trial evidence behind it. The other is a surfactant stool softener for which evidence of effectiveness is considerably less robust. This guide walks through what the actual research says about PEG 3350 vs Colace (docusate sodium), not just what the packaging implies.
For a shorter, brand-name-focused version of this comparison (MiraLAX vs Colace, including product sizes and where to buy), see our MiraLAX vs Colace quick comparison guide.
What PEG 3350 and Docusate Sodium Actually Are
PEG 3350 (polyethylene glycol 3350) is the active ingredient in MiraLAX and many store-brand polyethylene glycol 3350 products. It is a large, poorly absorbed polymer molecule. When dissolved in water and swallowed, it stays largely within the digestive tract, where it retains water in the stool as it moves through the colon.[6,7]
Studies tracking how much of an ingested dose shows up in urine have found only a small fraction is absorbed at all. The standard OTC label limits unsupervised use to 7 days, but longer, physician-directed use for chronic constipation is supported by clinical trial data, distinct from the OTC labeling itself.[1,7]
Docusate sodium (the active ingredient in Colace) works through a different mechanism. It is an anionic surfactant that is thought to lower surface tension at the oil-water interface of stool, and is thought to facilitate mixing of water into the stool to soften it.[2]
That proposed mechanism is why docusate has been sold as a “stool softener” since the 1950s, but it has not translated into strong clinical evidence of benefit. The problem, as later sections cover, is that the clinical trial evidence has not consistently backed up that theory in practice.
The Evidence: What the Research Actually Shows
PEG 3350: A Strong, Consistent Evidence Base
PEG 3350 is one of the better-supported OTC laxatives for chronic constipation. A 2021 systematic review of over-the-counter constipation therapies by gastroenterologists Satish Rao and Darren Brenner, published in the American Journal of Gastroenterology, graded PEG among the highest-evidence options reviewed.[2]
A 2010 Cochrane systematic review comparing PEG against lactulose (another osmotic laxative) across ten randomized trials and 868 participants found PEG outperformed lactulose on stool frequency, stool consistency, and relief of abdominal pain.[3]
Based on this body of evidence, the 2023 American Gastroenterological Association and American College of Gastroenterology (AGA/ACG) joint clinical practice guideline gives polyethylene glycol a strong recommendation, based on moderate-certainty evidence, for chronic idiopathic constipation in adults.[1]
Docusate Sodium: Popular, but Thin on Evidence
Docusate tells a very different story. Evidence supporting its effectiveness for chronic constipation is limited. The 2021 Rao and Brenner systematic review found insufficient evidence to establish docusate’s efficacy for chronic constipation, so it could not be assigned an evidence grade at all.[2]
A 2014 Canadian Agency for Drugs and Technologies in Health (CADTH) rapid review reached a similar conclusion, finding little evidence that docusate outperforms placebo on stool frequency or consistency.[5]
Reflecting this evidence gap, the 2023 AGA/ACG guideline did not make a recommendation for docusate because the evidence was insufficient to assess; the guideline states no formal assessment of surfactant laxatives or stool softeners was provided.[1]
This does not mean docusate is dangerous or useless. It means the specific claim on the label, that it treats constipation, has not been well established in trials. Docusate is still used in some postoperative settings when clinicians want to minimize straining, although evidence that it meaningfully improves constipation outcomes in that setting is also limited.
What a Direct Trial Found When PEG Was Added to Docusate
One of the more informative data points comes from a 2016 randomized controlled trial in 145 women recovering from urogynecologic surgery. All participants received docusate sodium twice daily, and were then randomized to also receive either PEG 3350 (66 women) or a placebo (65 women) for five days after surgery.[4]
Adding PEG 3350 to routine docusate did not significantly shorten the time to a first bowel movement compared with docusate plus placebo (2.77 days vs 2.92 days, P=.25), so the trial does not show that PEG sped up postoperative bowel recovery in this setting.[4]
Women in the PEG group did use fewer additional laxatives and were more adherent to the regimen, which were secondary findings, not the trial’s primary result. Because both study arms received docusate throughout, this trial cannot tell us how well docusate performs on its own; it was not designed to test that question.[4]
PEG 3350 vs Colace for Constipation: Side-by-Side Comparison
| Factor | PEG 3350 (generic equivalent of MiraLAX) | Docusate Sodium (generic equivalent of Colace) |
|---|---|---|
| Drug class | Osmotic laxative | Surfactant / emollient “stool softener” |
| Mechanism | Draws and holds water in the stool | Helps water mix into stool by lowering surface tension |
| Typical labeled onset | 1 to 3 days | 12 to 72 hours (per product labeling; ranges overlap substantially with PEG) |
| AGA/ACG 2023 guideline status | Strong recommendation, moderate-certainty evidence[1] | No recommendation made; evidence insufficient to assess[1] |
| Best-supported use | Chronic idiopathic constipation: strong guideline support; note that OTC labeling itself is for occasional constipation and a 7-day limit[1,7] | Sometimes used postoperatively to reduce straining; evidence of clinical benefit is limited |
| Long-term daily use | Clinical trials support efficacy and tolerability for several months, including studies lasting about 6 months; OTC self-treatment is still limited to 7 days unless directed by a doctor[1,2] | Not well studied long-term |
| Typical adult dose | 17 g powder dissolved in 4 to 8 oz liquid, once daily[7] | Commonly 100 mg softgels, 1 to 3 per day depending on product labeling[8] |
| Common side effects | Bloating, gas, mild cramping, loose or watery stools | Generally mild GI side effects; diarrhea or stomach cramping can occur |
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Generic vs Brand Name: Cost and Availability
Both ingredients are widely available as unbranded generic products, although availability and pricing vary by retailer and location.
PEG 3350: Store-brand polyethylene glycol 3350 (Equate, CVS Health, Up&Up, Walgreens brand) is typically less expensive than brand-name MiraLAX for the same dose count, and warehouse-club or larger bottles push the per-dose cost lower still.[10] Prices vary considerably by pharmacy, package size, region, and available coupons, so treat any specific dollar figure as a snapshot rather than a current price; check GoodRx, SingleCare, the pharmacy directly, or compare current polyethylene glycol 3350 options on Amazon for today’s price. (As an Amazon Associate, this site earns from qualifying purchases.)
Docusate sodium: Generic docusate sodium is widely available and is typically less expensive than brand-name Colace at the same strength.[9] As with PEG, exact prices shift by retailer and location, so check current listings, including docusate sodium options on Amazon, rather than relying on a fixed number.
For an FDA-approved generic drug, the generic must meet FDA standards for quality and bioequivalence to the corresponding brand-name product. When the generic and brand contain the same active ingredient in the same strength and dosage form, the generic is generally expected to provide the same therapeutic effect when used as labeled, so choosing generic is a straightforward way to cut cost.
Which One Should You Choose?
Choose PEG 3350 if:
- You have constipation that keeps coming back, not just an isolated episode
- You want one of the best-supported OTC options for actually increasing bowel movement frequency
- You need something suitable for daily or near-daily use over weeks to months, ideally with medical guidance beyond the standard 7-day OTC window
- You prefer a powder that can be mixed into a beverage rather than swallowing capsules
If you’d rather address constipation through fiber instead of an osmotic laxative, our comparison of MiraLAX and fiber-based Metamucil covers that trade-off.
Docusate sodium may be considered if:
- Your clinician specifically recommends it as part of a postoperative bowel regimen or when avoiding straining is a priority, while recognizing that evidence for docusate’s effectiveness is limited
- You are directed to take it alongside another laxative rather than as a stand-alone treatment, which is one setting in which docusate has been studied[4]
For a broader side-by-side across every major OTC option, not just these two, see our full guide to the best OTC laxatives for constipation, and our dedicated breakdown of stool softeners and how their evidence compares.
Can You Take PEG 3350 and Docusate Together?
Yes, people commonly do, and this combination is the one that has actually been tested directly, in the 2016 postoperative trial described above.[4] That trial found adding PEG to routine docusate did not significantly speed up the first bowel movement, though it did reduce how often patients needed additional laxatives.
In practice, some clinicians still use both after surgery because they have different mechanisms, although the evidence that combining them provides meaningful additional benefit is limited. If you are recovering from surgery or childbirth, follow whatever regimen your care team gives you rather than combining laxatives on your own.
Safety Considerations
Both are generally well tolerated when used as directed, but their evidence for effectiveness is very different. The PEG 3350 Drug Facts label specifically instructs people with kidney disease not to use it except under the advice and supervision of a doctor, and advises checking with a doctor first if nausea, vomiting, or abdominal pain are present, since these can be symptoms of bowel obstruction rather than ordinary constipation.[7]
PEG 3350 should also not be used for more than 7 days unless directed by a doctor; the standard OTC label states this directly, and longer, physician-directed use for chronic constipation management is a separate, medically supervised context. Docusate can cause gastrointestinal side effects such as stomach cramps or diarrhea, although it is generally well tolerated; because its evidence base is thin, “well tolerated” mostly means low risk of harm rather than confirmed benefit.[5]
Constipation with rectal bleeding, severe or persistent abdominal pain, vomiting, inability to pass gas, or unexplained weight loss should be medically evaluated rather than treated solely with an OTC laxative.
Frequently Asked Questions
Is PEG 3350 the same thing as MiraLAX?
MiraLAX is a brand-name product containing polyethylene glycol 3350 (PEG 3350) as its active ingredient. Store-brand versions like Equate, CVS Health, and Up&Up ClearLax list the same active ingredient at the same strength, but always check the Drug Facts label to confirm.
Is docusate sodium the same thing as Colace?
Many Colace products contain docusate sodium as their active ingredient, and generic docusate sodium products contain the same active ingredient. Colace also sells combination products (such as a docusate-plus-sennosides formula), so check the Drug Facts label for the exact strength and formulation before assuming two products are equivalent.
Which works faster, PEG 3350 or docusate?
Their labeled onset windows overlap substantially: docusate is labeled to generally produce a bowel movement within 12 to 72 hours, while PEG 3350 is labeled for 1 to 3 days. Labeled onset time is not the same as proven effectiveness, and PEG has considerably stronger evidence that it actually improves constipation.
If rapid relief is the priority, other OTC options, including some saline or stimulant laxatives like bisacodyl (see our MiraLAX vs Dulcolax comparison), generally have faster labeled onset than either of these two.
Can I take PEG 3350 every day long-term?
PEG 3350 has been studied for use beyond the standard OTC label period, including trials lasting about 6 months.[1,2] However, the standard OTC label says not to use it for more than 7 days unless directed by a doctor. If you need it regularly beyond that, loop in a doctor.
Why do doctors still recommend docusate if the evidence is weak?
Docusate has been used for decades, is inexpensive, and is generally well tolerated, and its continued use may partly reflect established clinical habit rather than strong trial evidence. It is less that docusate has been disproven and more that it has never been proven to work for constipation to the same standard as PEG.
References
- Chang L, Chey WD, Imdad A, et al. American Gastroenterological Association-American College of Gastroenterology clinical practice guideline: pharmacological management of chronic idiopathic constipation. Am J Gastroenterol. 2023. doi:10.14309/ajg.0000000000002227
- Rao SSC, Brenner DM. Efficacy and safety of over-the-counter therapies for chronic constipation: an updated systematic review. Am J Gastroenterol. 2021;116(6):1156-1181. doi:10.14309/ajg.0000000000001222
- Lee-Robichaud H, Thomas K, Morgan J, Nelson RL. Lactulose versus polyethylene glycol for chronic constipation. Cochrane Database Syst Rev. 2010;(7):CD007570.
- Edenfield AL, Siddiqui NY, Wu JM, Dieter AA, Garrett MA, Visco AG. Polyethylene glycol 3350 and docusate sodium compared with docusate sodium alone after urogynecologic surgery: a randomized controlled trial. Obstet Gynecol. 2016;128(3):543-549. PMID: 27500338
- Canadian Agency for Drugs and Technologies in Health. Dioctyl sulfosuccinate or docusate (calcium or sodium) for the prevention or management of constipation: a review of the clinical effectiveness. Ottawa: CADTH; 2014.
- MedlinePlus. Polyethylene glycol 3350. Bethesda: National Library of Medicine. medlineplus.gov/druginfo/meds/a603032.html
- Mayo Clinic. Polyethylene glycol 3350 (oral route): description and dosing. mayoclinic.org
- National Library of Medicine, DailyMed. Docusate sodium 100 mg softgel capsule, OTC drug facts label. dailymed.nlm.nih.gov
- SingleCare. Docusate sodium and Colace price comparisons (pricing information current as of publication; verify current prices before relying on any figure).
- GoodRx / SingleCare. MiraLAX and polyethylene glycol 3350 price comparisons (pricing information current as of publication; verify current prices before relying on any figure).
This article is for informational purposes only and is not a substitute for professional medical advice. Always read product labels and consult a healthcare provider before starting any new laxative, especially if you have kidney disease, are pregnant, or are on a sodium-restricted diet.
