Both Prevacid and Prilosec are proton pump inhibitors that work by inhibiting the proton pumps in the stomach that produce acid. They treat the same medical issues, those primarily associated with over-production of acid in the stomach and the resultant effects. In a study of the two drugs that tested their efficacy on patients suffering from gastroesophageal reflux disease (GERD), Prevacid was found to be more effective at normalizing acid exposure in the esophagus. However, Prevacid is more expensive than Prilosec, costing a minimum of $38 a month, while Prilosec costs around $10 monthly.

Comparison chart

Prevacid versus Prilosec comparison chart
Edit this comparison chartPrevacidPrilosec
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Active Ingredient Lansoprazole. Omeprazole.
Conditions treated Treats gastroesophageal reflux disease (GERD), surplus acid, ulcers, heartburn. Duodenal ulcers, stomach ulcers, GERD, and erosive esophagitis, intially Zollinger-Ellison Syndrome.
Drug Type Proton Pump Inhibitors (PPI). Proton Pump Inhibitors (PPI).
Prescription Over-the-counter or prescription. Over-the-counter or prescription.
Generic Version Available. Available.
Side Effects Constipation, nausea, headache, dizziness. Headache, diarrhea, nausea, risk of bone fractures, stomach lining inflammation.
Dose 15mg once a day for 4 weeks for short-term treatment; 15mg once daily for maintenance. 2 times daily for 10 days; once a day for 18 days if ulcer is present.
Pregnancy Category B (USA): Animal studies have shown no effects on fertility or fetotoxicity; however, no studies exist on human use when pregnant. Should only be used while pregnant if benefits outweigh risks. C (USA): Not safe during pregnancy, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
Delayed reslease Yes. Yes.
How it Works Blocks production of acid in stomach. Blocks production of acid in stomach.
Form 15 and 30mg capsules; 15 and 30mg orally-disintegrating tablets. 2.5 mg suspension, 10 mg suspension, 10 mg, 20 mg, 40 mg delayed-release capsules.
Cost 15mg pills, 30-count, starting at $38. 20 mg pills, 30-count, starting at $10.05.
Efficacy Significant inhibition of acid production. Significant inhibition of acid production.
Time Lapse 1-4 days for full effect. 1-4 days for full effect.
Overdose Symptoms Confusion, drowsiness, blurred vision, fast or pounding heartbeat, nausea, vomiting, sweating, flushing (feeling of warmth), headache, dry mouth. Confusion, drowsiness, blurred vision, fast or pounding heartbeat, nausea, vomiting, sweating, flushing (feeling of warmth), headache, dry mouth.
Withdrawal Symptoms Can cause acid reflux. Can cause acid reflux.
Shelf Life 3 years. 3 years.
FDA Approval Prescription – 1995, OTC - 2012. Prescription – 1989, OTC - 2010.


As proton pump inhibitors, both Prevacid and Prilosec are good at treating gastroesophageal reflux disease (GERD), a condition in which backward flow of acid from the stomach causes heartburn and possible injury of the esophagus. The two drugs also treat a general surplus of acid in the stomach (heartburn) and ulcers. Both are available as a prescription or over-the-counter. The only difference between the prescription form and the OTC form of both Prevacid and Prilosec is the dosage.

The following video further explains how proton pump inhibitors work.


Prevacid comes as 15 and 30mg capsules as well as 15 and 30mg orally-disintegrating tablets. Prilosec comes as a 2.5mg suspension, a 10mg suspension, and 10, 20, or 40mg delayed-release capsules.

Directions for Use

Both drugs should be taken orally or as directed by a doctor, usually once daily before a meal. Prevacid may be administered via feeding tube. Prilosec may be given through a tube into the stomach.

Storage and Shelf Life

Both Prevacid and Prilosec should be stored at room temperature, away from light, excessive heat, and moisture. If stored this way, Prevacid and Prilosec can last for up to three years.


Both Prevacid and Prilosec show significant inhibition in the production of acid in the stomach. They begin working within 24 hours, but up to four days may pass before their effects are noticeable. Over long-term use, Prevacid is more effective than Prilosec.

Side Effects

Common side effects for Prevacid and Prilosec are the same, including constipation, gas, nausea, vomiting and headache. Rare but severe side effects include excessive tiredness, dizziness, lightheadedness, muscle spasms, uncontrollable shaking of a part of the body, seizures, diarrhea with watery stools, stomach pain, fever, and irregular, fast, or pounding heartbeat.

Allergic Reaction

Prevacid, Prilosec, Nexium vs Prilosec, and Zantac may produce allergic reactions such as difficulty or pain in swallowing, skin rash, hives, itching, difficulty breathing, hoarseness, and swelling of the face, throat, tongue, lips, eyes, hands, feet, ankles, or lower legs. Patients with any of these symptoms should seek medical help immediately.


Prilosec has a greater potential to cause allergic reactions, but patients with allergies to lansoprazole should not take Prevacid. For either drug, patients should warn their doctors if they have a history of liver disease. Potential Prevacid users need to tell their doctors of any previous medical history that includes lightheadedness, sweating, or dizziness along with the heartburn; chest pain or shoulder pain; shortness of breath or wheezing; pain that spreads to the arms, neck, or shoulders; unexplained weight loss; nausea or vomiting.

Usage of PPIs may make patients more susceptible to broken bones.

Drug Interactions

Prevacid and Prilosec may interact with the following medications: certain antibiotics, including Ampicillin (Principen, in Unasyn); anticoagulants such as Warfarin (Coumadin); Atazanavir (Reyataz); Digoxin (Lanoxicaps, Lanoxin); diuretics; iron supplements; Ketoconazole (Nizoral); Methotrexate (Rheumatrex, Trexall); and and Tacrolimus (Prograf).

Prevacid may also interact with Theophylline (Theo-bid, TheoDur), while Prilosec may also interact with benzodiazepines such as Diazepam (Valium); Cilostazol (Pletal); Clopidogrel (Plavix); Cyclosporine (Neoral, Sandimmune); Disulfiram (Antabuse); Nelfinavir (Viracept); Phenytoin (Dilantin); Saquinavir (Invirase); Voriconazole (Vfend), and other prescription antifungal or anti-yeast medications.

Overdose and Withdrawal Symptoms

Patients can experience overdose symptoms with both Prevacid and Prilosec, which include confusion, drowsiness, blurred vision, fast or pounding heartbeat, nausea, vomiting, sweating, flushing, headache and dry mouth. Patients who stop taking either Prevacid or Prilosec may experience the return of regular heartburn and other symptoms of the original illness. Ending Prevacid or Prilosec use may cause acid reflux.


As an example of cost, a 30-count package of 15mg Prevacid capsules starts at $38 at most pharmacies, while a similar supply of 20mg Prilosec capsules start at $10.05. Both are one-month supplies. The drugs may be found more cheaply online in some cases.


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