Alternatives to Kristalose If You Can't Fill Your Prescription

When Kristalose isn't available at your pharmacy and you can't wait days for a special order, knowing your alternatives can make the difference between getting relief and going without treatment. The good news is that several highly effective options exist — some available over the counter and some requiring a prescription — that your doctor can authorize as a substitute.

This guide reviews the best alternatives to Kristalose (lactulose powder) in 2026, covering how each works, who it's best for, costs, and what to ask your doctor.

Option 1: Generic Lactulose Solution (Constulose, Enulose, Generlac)

The most direct substitute for Kristalose is generic lactulose solution — the same active ingredient in liquid form. Brands include Constulose, Enulose, and Generlac, though your pharmacy may dispense it as simply "lactulose oral solution."

How it works: Identical mechanism to Kristalose — osmotic laxative that draws water into the colon

Typical dose: 15–30 mL (10–20g) once daily for constipation

Pros: Same therapeutic effect; widely available; significantly cheaper ($8–$15 with GoodRx vs. $100+ for brand Kristalose)

Cons: Liquid form (must measure doses); some patients find the syrup form less convenient or have difficulty measuring accurately

Prescription required: Yes

This is typically the easiest switch if you currently take Kristalose for constipation — your prescriber can call in a new prescription for generic lactulose the same day.

Option 2: MiraLAX (Polyethylene Glycol 3350)

MiraLAX is the most commonly recommended over-the-counter alternative to lactulose for chronic constipation. It contains polyethylene glycol 3350 (PEG 3350), also an osmotic laxative that draws water into the colon.

How it works: Osmotic action — retains water in stool without fermentation

Typical dose: 17g once daily dissolved in 8 oz of any beverage

Pros: OTC (no prescription), tasteless, causes less gas and bloating than lactulose, widely available

Cons: Only approved for short-term use (up to 7 days for OTC indication); does NOT treat hepatic encephalopathy

Cost: Approximately $10–$20 for a 30-dose supply OTC

Important note: If you take Kristalose specifically for hepatic encephalopathy (liver-related brain fog), MiraLAX is NOT an appropriate substitute. Only lactulose has FDA approval for that indication. Speak with your hepatologist or gastroenterologist before making any switch.

Option 3: Senna (Senokot)

Senna is an OTC stimulant laxative that works by triggering intestinal muscle contractions. It's faster-acting than lactulose but works through a different mechanism.

How it works: Stimulant laxative — irritates the colon to trigger contractions

Typical dose: 2 tablets (17.2mg) at bedtime, producing a movement in 6–12 hours

Pros: Fast-acting, inexpensive (~$5–$10 OTC), good for short-term relief

Cons: Can cause cramping; not recommended for long-term use; some evidence of tolerance with prolonged use; not for hepatic encephalopathy

Option 4: Bisacodyl (Dulcolax)

Another stimulant laxative available OTC, bisacodyl works quickly and is useful for short-term constipation relief when Kristalose is unavailable. Available as tablets (6–12 hour onset) or suppositories (within 1 hour).

Best for: Short-term, acute constipation relief while you work on finding your Kristalose

Cost: Approximately $8–$12 OTC

Option 5: Psyllium Husk (Metamucil, Konsyl)

Psyllium is a bulk-forming laxative (fiber supplement) that absorbs water and increases stool bulk. It's a gentle, long-term option suitable for chronic constipation management, though it works differently than lactulose.

Best for: Mild to moderate chronic constipation; patients who prefer a natural fiber option

Cost: ~$15–$25 OTC for a 30-day supply

When Is Lactulose the Only Option? (Hepatic Encephalopathy)

If you are taking lactulose (Kristalose) specifically to treat or prevent hepatic encephalopathy (a liver-related condition that can cause confusion, memory problems, and altered consciousness), do NOT substitute with OTC laxatives without your doctor's approval. Lactulose's ability to acidify the colon and reduce ammonia absorption is a specific therapeutic effect not replicated by MiraLAX, senna, bisacodyl, or fiber supplements.

In this case, generic lactulose liquid is your best and most direct substitute. Your hepatologist or gastroenterologist can authorize a same-day prescription.

What to Tell Your Doctor When Requesting an Alternative

When calling your doctor's office, say: "My pharmacy doesn't have Kristalose in stock. Can you authorize a switch to generic lactulose liquid or another alternative while I work on finding it?" Keep looking for Kristalose while on a temporary substitute — services like medfinder can help you find which pharmacies near you carry Kristalose so you can return to your preferred medication as soon as possible.