Prilosec and Zantac block the production of acid in the stomach but the drugs have different mechanisms of action. Studies that tested both drugs found that both effectively treated heartburn symptoms, but Prilosec provided greater resolution of heartburn symptoms at 2 to 4 weeks. Both are available as a prescription or over-the-counter, depending on the dosage.

Comparison chart

Prilosec versus Zantac comparison chart
Edit this comparison chartPrilosecZantac
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Active Ingredient Omeprazole. Ranitidine
Conditions treated Duodenal ulcers, stomach ulcers, GERD, and erosive esophagitis, intially Zollinger-Ellison Syndrome. Gastroesophageal reflux disease (GERD), surplus acid, ulcers, heartburn
Drug Type Proton Pump Inhibitors (PPI). H2RA histamine blocker
Prescription Over-the-counter or prescription. Over the counter or prescription
Generic Version Available. Available
Side Effects Headache, diarrhea, nausea, risk of bone fractures, stomach lining inflammation. Headache, dizziness, constipation or diarrhea
Dose 2 times daily for 10 days; once a day for 18 days if ulcer is present. Once or twice daily, but it may be prescribed for up to four times a day.
Pregnancy Category C (USA): Not safe during pregnancy, but potential benefits may warrant use of the drug in pregnant women despite potential risks. B (USA): Safe during pregnancy.
How it Works Blocks production of acid in stomach. Blocks production of acid in stomach
Form 2.5 mg suspension, 10 mg suspension, 10 mg, 20 mg, 40 mg delayed-release capsules. 150 mg tablet, 300 mg tablet, effervescent tablet, effervescent granules, syrup.
Cost 20 mg pills, 30-count, starting at $10.05. 150 mg tablets, 30-count starting at $4
Efficacy Significant inhibition of acid production. Significant inhibition of acid production
Time Lapse 1-4 days for full effect. Within 24 hours
Delayed reslease Yes. No
Overdose Symptoms Confusion, drowsiness, blurred vision, fast or pounding heartbeat, nausea, vomiting, sweating, flushing (feeling of warmth), headache, dry mouth. Difficulty walking, severe dizziness/fainting
Withdrawal Symptoms Can cause acid reflux. Rebound dyspepsia
Shelf Life 3 years. 5 years
FDA Approval Prescription – 1989, OTC - 2010. 1998


Both Prilosec and Zantac are used to treat gastroesophageal reflux disease (GERD), a condition in which backward flow of acid from the stomach causes heartburn and possible injury of the esophagus. They also treat surplus acid in the stomach, ulcers and heartburn.

Prilosec (generic name omeprazole) is a Proton Pump Inhibitor (PPI), meaning it blocks the production of acid in the stomach. Zantac (generic name ranitidine), is an H2 histamine blocker, meaning it blocks the production of acid in the stomach.


Prilosec is available as 2.5 mg suspension, 10 mg suspension, and 10, 20 or 40 mg delayed-release capsules.

Zantac is available in 150 and 300 mg tablets, effervescent tablets, effervescent granules and a syrup.

Directions for Use

Prilosec should be taken orally or as directed by a doctor, usually once daily before a meal. It may be given through a tube into the stomach.

Zantac is also taken orally, with or without food. Patients usually take it once or twice daily, but it may be prescribed for up to four times a day.

Storage and Shelf Life

Both Prilosec and Zantac should be stored at room temperature, away from light, excess heat and moisture. If stored this way, Prilosec lasts three years and Zantac lasts five years.


Both Prilosec and Zantac were tested in a multicenter, randomized, open-label, medical effectiveness trial conducted in five university-based family medicine clinics. Both show significant inhibition in the production of acid in the stomach. Zantac starts working within 24 hours. Prilosec also starts working within 24 hours, though it may take from one to four days for the full effect. Over long-term use, Prilosec is more effective. [1]

Side Effects

Common side effects for Prilosec include 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.

Zantac may have side effects like headache, dizziness, constipation or diarrhea. Rare but severe side effects include blurred vision, easy bleeding or bruising, enlarged breasts, severe tiredness, severe stomach or abdominal pain, dark urine and yellowing skin or eyes. Other severe side effects include mental or mood changes such as agitation, confusion, depression, and hallucinations; changes in heartbeat; and signs of infection such as fever, persistent sore throat and cough.

Allergic Reaction

Both Prilosec and Zantac may produce allergic reactions such as difficulty or pain in swallowing and/or a skin rash. Other symptom of allergic reactions for Prilosec include 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.


Overdose of Prilosec may result in confusion, drowsiness, blurred vision, fast or pounding heartbeat, nausea, vomiting, sweating, flushing, headache, and dry mouth. Symptoms of Zantac overdose include difficulty walking, severe dizziness and fainting.

Withdrawal Symptoms

Patients who stop taking either Prilosec or Zantac may experience the return of regular heartburn and other symptoms of the original illness. Stoppage of Prilosec may cause acid reflux, while stoppage of Zantac may cause rebound dyspepsia.


Patients allergic to the following drugs should not take Prilosec: omeprazole, dexlansoprazole (Dexilant), esomeprazole (Nexium), lansoprazole (Prevacid), pantoprazole (Protonix) and rabeprazole (Aciphex). Patients should also warn their doctors if they have a history of liver disease. Patients with allergies to ranitidine should not take Zantac. They should warn their doctors if they have a history of porphyria, phenylketonuria or kidney or liver disease.

Drug Interactions

Prilosec may interact with the following medications: certain antibiotics, including ampicillin (Principen, in Unasyn);anticoagulants such as warfarin (Coumadin); atazanavir (Reyataz); benzodiazepines such as diazepam (Valium); cilostazol (Pletal); clopidogrel (Plavix); cyclosporine (Neoral, Sandimmune); digoxin (Lanoxicaps, Lanoxin) disulfiram (Antabuse); diuretics; iron supplements; ketoconazole (Nizoral); methotrexate (Rheumatrex, Trexall), nelfinavir (Viracept); phenytoin (Dilantin); saquinavir (Invirase); tacrolimus (Prograf); and voriconazole (Vfend) and other prescription antifungal or anti-yeast medications. Zantac may interact with the following medications: atazanavir, delavirdine, dasatinib, gefitinib, glipizide, raltegravir, triazolam, azole antifungals such as ketoconazole, aspirin or aspirin-like NSAIDs.


A 30-count package (one-month supply) of 20 milligram Prilosec pills starts at $10.05. A 30-count package ( one-week to one-month supply) of 150 milligram Zantac tablets starts at $4.


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