Prilosec vs Prevacid: Which Is Better for Heartburn?

Prilosec (omeprazole) and Prevacid (lansoprazole) are both proton pump inhibitors (PPIs), and they work about equally well. Over the counter, Prilosec OTC contains omeprazole 20 mg and Prevacid 24HR contains lansoprazole 15 mg. Both are taken once a day before breakfast for 14 days. In head-to-head trials for healing reflux damage, standard prescription doses produced almost identical results. The practical differences are formats (Prevacid comes as a dissolving tablet), drug interactions, and price, which favors generics of either.

If you’re standing in the pharmacy aisle choosing between the two, the honest answer is that for most people it doesn’t matter much. Below I explain how they compare on effectiveness, dosing, side effects and interactions, the situations where one may suit you better, and why neither is the full answer for silent reflux.

Key Takeaways

• Both are PPIs that block the stomach’s acid pumps. They differ in the active drug, not the mechanism.
• Prilosec OTC: omeprazole 20 mg. Prevacid 24HR: lansoprazole 15 mg.
• Both OTC versions are for frequent heartburn (2 or more days a week): 1 capsule a day before eating in the morning, for 14 days, repeatable every 4 months.
• A meta-analysis of six trials found that healing rates for erosive esophagitis were not significantly different between omeprazole 20 mg and lansoprazole 30 mg (about 87% vs 89% at 8 weeks).
• Neither gives instant relief. Full effect takes 1 to 4 days.
• Prevacid is available as an orally disintegrating tablet (SoluTab) for people who struggle to swallow capsules.
• Omeprazole has some notable interactions, particularly with clopidogrel, so check with a pharmacist if you take other medicines.
• For silent reflux (LPR), PPIs often disappoint because they reduce acid but don’t stop reflux or pepsin reaching the throat.

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Prilosec vs Prevacid at a Glance

Prevacid 24HR directions are from its Drug Facts label [Prevacid 24HR label].

Which Is More Effective?

For healing erosive esophagitis, a meta-analysis of six randomized, double-blind trials compared the standard prescription doses: omeprazole 20 mg and lansoprazole 30 mg. Healing rates were 74.7% and 77.7% at 4 weeks and 87.0% and 88.7% at 8 weeks (per protocol), with no statistically significant difference [Sharma et al., Alimentary Pharmacology & Therapeutics, 2001].

In other words, at standard doses they perform about the same. Individual responses vary, though. Some people find one works better for them, and switching is a reasonable step if one isn’t helping.

Is Prevacid 15 mg weaker than Prilosec 20 mg?

Not in any meaningful way for OTC use. The doses aren’t equivalent milligram for milligram because they’re different molecules. The OTC strengths of both were approved as effective for frequent heartburn.

How to Take Them

• Take it once a day, 30 to 60 minutes before breakfast. PPIs work best when the acid pumps are activated by a meal. See best time of day to take omeprazole.
• Swallow it whole with water (or let a SoluTab dissolve on your tongue).
• Expect full effect after 1 to 4 days. See how long omeprazole takes to work.
• Over the counter, take it for 14 days, no more often than every 4 months unless your doctor says otherwise.

Side Effects

Both share typical PPI side effects: headache, diarrhea, nausea, abdominal pain and constipation. See do acid reducers cause constipation? Long-term use of any PPI has been linked to lower B12 and magnesium levels, bone density concerns and some gut infections. See PPIs and bone density and PPIs and infection risk. These concerns apply to the class, not one drug.

For more detail, see omeprazole side effects and lansoprazole for acid reflux.

Drug Interactions

All PPIs can change the absorption of drugs that need stomach acid, such as some antifungals and HIV medicines. Omeprazole has a particularly notable interaction with the blood thinner clopidogrel (Plavix), because it can reduce clopidogrel’s activation, and the FDA has advised against combining them. If you take clopidogrel, your doctor may prefer a different PPI. Always check with a pharmacist. See omeprazole drug interactions.

When You Might Choose One Over the Other

• Trouble swallowing pills: Prevacid SoluTab dissolves on the tongue. Omeprazole is also available as a suspension, and see Zegerid for an immediate-release omeprazole powder.
• Taking clopidogrel: ask your doctor about avoiding omeprazole.
• Cost: generic omeprazole is usually the cheapest PPI. Generic lansoprazole is also inexpensive.
• One isn’t working: switching PPIs or adjusting timing is a common next step before moving to other options. See Prilosec vs Nexium, pantoprazole, Dexilant and Voquezna.

Prilosec or Prevacid vs Pepcid

PPIs are stronger and longer-lasting than H2 blockers like Pepcid (famotidine), but they take days to reach full effect. Pepcid works within an hour and suits occasional or predictable heartburn. See famotidine vs omeprazole.

Pregnancy

Both have been used in pregnancy when needed, but most providers start with lifestyle changes, antacids or an H2 blocker. Discuss it with your provider. See is omeprazole safe in pregnancy?

What About Silent Reflux (LPR)?

If your symptoms are in the throat (hoarseness, throat clearing, a lump sensation, chronic cough), switching between Prilosec and Prevacid rarely makes much difference. PPIs reduce how acidic the refluxate is, but they don’t stop reflux happening, and pepsin reaching the throat can still be reactivated by acidic food and drink. See why PPIs don’t work for LPR.

Stopping a PPI

After several weeks or more, stopping abruptly can cause rebound acid that feels like your reflux returning. Taper gradually with your doctor’s guidance. See getting off PPIs and acid rebound.

Conclusion

Prilosec (omeprazole) and Prevacid (lansoprazole) are closely matched PPIs. At standard doses they heal reflux damage at almost identical rates, both take a few days to work fully, and both follow the same 14-day OTC course. Choose based on practical factors: Prevacid SoluTab if you struggle to swallow capsules, avoid omeprazole if you take clopidogrel, and go with whichever generic is cheapest otherwise.

Whichever PPI you take, it lowers acid but doesn’t stop reflux. If you’ve been relying on one for months, the most effective long-term step is reducing how much reflux you have through what and when you eat. The Wipeout Diet Plan gives you a step-by-step, low-acid way to eat. I built it around LPR, the hardest form of reflux to control, and it works just as well for GERD and everyday heartburn.

Frequently Asked Questions

Is Prilosec or Prevacid better?

Neither is clearly better. At standard doses, trials show nearly identical healing rates for reflux damage. Choose based on format, interactions and price, or try the other if one doesn’t work for you.

Is Prevacid the same as omeprazole?

No. Prevacid is lansoprazole, a different PPI from omeprazole (Prilosec). They work the same way but aren’t the same molecule.

Can I take Prilosec and Prevacid together?

No. Taking two PPIs together adds side effect risk without meaningful benefit. Use one as directed.

Which works faster, Prilosec or Prevacid?

Neither works immediately. Both may take 1 to 4 days for full effect. For fast relief, use an antacid or alginate.

Can I switch from Prilosec to Prevacid?

Yes. Switching between PPIs is common if one isn’t working well or causes side effects. Check with your doctor or pharmacist first, especially if you take other medicines.

Is Prevacid 15 mg the same strength as Prilosec 20 mg?

They’re different drugs, so the milligrams don’t compare directly. Both OTC strengths are approved as effective for frequent heartburn.

Does Prevacid have fewer side effects than Prilosec?

Their side effect profiles are very similar. Omeprazole has some more notable drug interactions, particularly with clopidogrel.

Research & References

• The US Drug Facts label for Prevacid 24HR (lansoprazole 15 mg), including once-daily morning dosing, the 14-day course and repeating every 4 months [Prevacid 24HR label].
• A meta-analysis of six randomized, double-blind trials finding no statistically significant difference in erosive esophagitis healing between omeprazole 20 mg and lansoprazole 30 mg (87.0% vs 88.7% at 8 weeks, per protocol) [Sharma et al., Alimentary Pharmacology & Therapeutics, 2001].

David Gray

12 years living with LPR · Consultant & researcher

Every claim sourced to peer-reviewed research Editorial policy

I've lived with LPR for twelve years — the misdiagnoses, the PPI courses that did nothing, the slow work of figuring out what actually helps. Wipeout Reflux is where I translate the research into plain terms for people stuck in the same place. Every claim here is sourced to peer-reviewed work, and I consult one-to-one with LPR sufferers.

View all articles by David Gray