Alternatives to Bisacodyl If You Can't Fill Your Prescription

When Bisacodyl (Dulcolax) isn't available at your pharmacy, you have several effective alternatives to choose from. The best choice depends on how quickly you need relief, how long you'll be using a laxative, and any underlying health conditions. This guide breaks down the top options, how they work, and when to choose each one.

Quick Comparison: Bisacodyl Alternatives at a Glance

Here's how the most common alternatives compare to Bisacodyl:

Senna (Senokot, Ex-Lax): Stimulant laxative. Onset 6–12 hours. Best direct substitute for bisacodyl.

Polyethylene glycol 3350 / MiraLAX: Osmotic laxative. Onset 1–3 days. Gentler, preferred for chronic constipation.

Magnesium hydroxide (Milk of Magnesia): Saline laxative. Onset 30 min–6 hours. Fast-acting; use with caution in kidney disease.

Docusate sodium (Colace): Stool softener. Onset 12–72 hours. Best for preventing constipation, not treating active episodes.

Psyllium (Metamucil): Bulk-forming fiber supplement. Onset 12–72 hours. Best for long-term regularity. Drink plenty of water.

Option 1: Senna — The Closest Equivalent to Bisacodyl

Senna is the most direct alternative to bisacodyl. Like bisacodyl, it's a stimulant laxative — it works by stimulating the muscles of the colon to contract and push stool through. The onset for oral senna is similar to bisacodyl: roughly 6–12 hours. Senna is widely available under brand names like Senokot, Ex-Lax, and Nature's Remedy, and it's stocked at virtually every pharmacy and grocery store.

For most people with occasional constipation, senna works just as well as bisacodyl. A 2021 systematic review published in the American Journal of Gastroenterology found good evidence supporting senna for chronic constipation, with similar performance to bisacodyl for relieving symptoms. Senna is the best first choice if you simply can't find bisacodyl.

Option 2: MiraLAX (Polyethylene Glycol 3350) — Best for Gentler Relief

MiraLAX (polyethylene glycol 3350, or PEG 3350) is an osmotic laxative that works differently than bisacodyl. Rather than stimulating intestinal contractions, it draws water into the colon to soften stool. MiraLAX takes longer to work — typically 1 to 3 days — but causes fewer cramps and is generally better tolerated for ongoing use.

MiraLAX is widely regarded as a first-choice laxative for chronic constipation and has Grade A evidence from clinical trials. It's the right choice if you need relief over a few days rather than overnight, or if bisacodyl has caused uncomfortable cramping for you in the past.

Option 3: Milk of Magnesia — Fast-Acting Option

Magnesium hydroxide (Milk of Magnesia) is a saline laxative that works by drawing water into the intestines, producing a bowel movement within 30 minutes to 6 hours. It's one of the faster OTC options available. However, it should be used with caution in people with kidney disease, as impaired kidneys may not effectively clear the magnesium. Talk to your doctor if you have any kidney issues before using magnesium-based laxatives.

Option 4: Docusate Sodium (Colace) — For Prevention, Not Active Relief

Docusate sodium (Colace) is a stool softener, not a laxative in the traditional sense. It works by allowing water and fats to penetrate stool more easily, making it softer and easier to pass. The key thing to know: docusate is NOT effective for actively treating constipation. It's best used to prevent hard stools or in situations where straining should be avoided (e.g., after surgery or childbirth). If you're backed up right now, docusate alone won't provide the relief you need.

When Should I Consider a Prescription Alternative?

If OTC laxatives — including bisacodyl alternatives — aren't providing adequate relief, talk to your doctor. Prescription options for chronic constipation include:

Linaclotide (Linzess): FDA-approved for chronic idiopathic constipation and IBS-C. Increases fluid secretion in the intestine.

Lubiprostone (Amitiza): FDA-approved for chronic idiopathic constipation; activates chloride channels to increase fluid in the bowel.

Lactulose: Prescription osmotic laxative that draws water into the colon; may cause more bloating than MiraLAX.

Bottom Line: Which Bisacodyl Alternative Should I Choose?

For most people who simply need to substitute for bisacodyl tablets, senna is the best and most direct replacement. If you'd prefer a gentler option, try MiraLAX. And if you still want to find bisacodyl itself, see our guide to finding Bisacodyl in stock near you before switching to an alternative.