Which one works faster?

Neither label states an onset time in minutes, so this page cannot give one. What the labels do differ on is what they allow: Pepcid AC may be taken 15 to 60 minutes before food expected to cause heartburn, while Prilosec OTC states that it is not intended for immediate relief and may take 1 to 4 days for full effect.

Can they be taken together?

The Pepcid AC label says not to use it with other acid reducers. Anyone whose heartburn is not controlled by one product is directed by both labels to a doctor.

Is famotidine the same as ranitidine?

They belong to the same class of histamine-2 receptor antagonists, but they are different molecules with different labels, and this page is built only from the documents it links. Ranitidine products were withdrawn from the US market and are not covered here.

Comparison

Pepcid AC vs Prilosec OTC

Pepcid AC

FAMOTIDINE

Approved forRelieving and preventing heartburn

Covers heartburn

Kenvue Brands LLCLabel version 20, effective 6 February 2026

Prilosec OTC

OMEPRAZOLE MAGNESIUM

Approved forFrequent heartburn, as a 14-day course

Covers heartburn

The Procter & Gamble Manufacturing CompanyLabel version 17, effective 1 October 2025

Each stripe is one section of the label, each division in a stripe one entry in that section.

Reference information, not medical advice

This page is a reference, not medical advice. It reports what the FDA-approved label states and links to that label. It does not tell anyone what to take, and it cannot replace a conversation with a doctor or pharmacist who knows the person's history.

These two products sit next to each other on the same shelf and are not the same kind of medicine. The clearest way to see the difference is not the class name but the instructions: one label lets you take it in advance, the other does not.

Side by side, straight from the labels

From the FDA label

This table is generated from the two source labels, not typed out by hand, so it cannot drift from what the regulator approved.

Label section	Pepcid ACFAMOTIDINE	Prilosec OTCOMEPRAZOLE MAGNESIUM
Active ingredient	FamotidineHistamine-2 receptor antagonist	OmeprazoleProton pump inhibitor
Approved for	Relieving and preventing heartburn	Frequent heartburn, as a 14-day course
Supply	Over the counter	Over the counter
What pharmacies payAcquisition cost, not retail	not listed	$14.78 per tablet, capsule or pen, brand
Boxed warning	None	None
What this product is for	Acid reducer relieves heartburn associated with acid indigestion and sour stomach prevents heartburn associated with acid indigestion and sour stomach brought on by eating or drinking certain food and beverages	Acid reducer treats frequent heartburn (occurs 2 or more days a week) not intended for immediate relief of heartburn; this drug may take 1 to 4 days for full effect
Active ingredient (in each tablet)	Famotidine 10 mg	Omeprazole delayed-release tablet 20 mg (equivalent to 20.6 mg omeprazole magnesium)
Directions	adults and children 12 years and over: to relieve symptoms, swallow 1 tablet with a glass of water. Do not chew. to prevent symptoms, swallow 1 tablet with a glass of water at any time from 15 to 60 minutes before eating food or drinking beverages that cause heartburn do not use more than 2 tablets in 24 hours children under 12 years: ask a doctor	for adults 18 years of age and older this product is to be used once a day (every 24 hours), every day for 14 days it may take 1 to 4 days for full effect; some people get complete relief of symptoms within 24 hours 14-Day Course of Treatment swallow 1 tablet with a glass of water before eating in the morning take every day for 14 days do not take more than 1 tablet a day do not use for more than 14 days unless directed by your doctor swallow whole. Do not chew, crush, or suck tablets. you may repeat a 14-day course every 4 months do not take for more than 14 days or more often than every 4 months unless directed by a doctor children under 18 years of age: ask a doctor. Heartburn in children may sometimes be caused by a serious condition.
Stop use and ask a doctor if	your heartburn continues or worsens you need to take this product for more than 14 days	• your heartburn continues or worsens • you need to take this product for more than 14 days • you need to take more than 1 course of treatment every 4 months • you get diarrhea • you develop a rash or joint pain
Warnings	had heartburn over 3 months. This may be a sign of a more serious condition. heartburn with lightheadedness, sweating, or dizziness chest pain or shoulder pain with shortness of breath; sweating; pain spreading to arms, neck or shoulders; or lightheadedness frequent chest pain frequent wheezing, particularly with heartburn unexplained weight loss nausea or vomiting stomach pain kidney disease	had heartburn over 3 months. This may be a sign of a more serious condition. frequent wheezing, particularly with heartburn unexplained weight loss nausea or vomiting stomach pain
Do not use	if you have trouble or pain swallowing food, vomiting with blood, or bloody or black stools. These may be signs of a serious condition. See your doctor. with other acid reducers	trouble or pain swallowing food, vomiting with blood, or bloody or black stools heartburn with lightheadedness, sweating or dizziness chest pain or shoulderpain with shortness of breath; sweating; pain spreading to arms, neck, or shoulders; or lightheadedness frequent chest pain
Label version	6 February 2026	1 October 2025

One prevents, the other treats a course

Written by us

The Pepcid AC label covers two uses: relieving heartburn associated with acid indigestion and sour stomach, and preventing it when brought on by eating or drinking certain foods and beverages. For prevention it gives a window, one tablet at any time from 15 to 60 minutes before the food or drink in question, with no more than two tablets in 24 hours.

The Prilosec OTC label has no such option. It authorises one tablet a day, every day, for 14 days, and states in its own words that the product is not intended for immediate relief of heartburn and may take 1 to 4 days for full effect.

Different classes, and the labels say so

Written by us

Famotidine is a histamine-2 receptor antagonist. Its prescription label describes it as a competitive inhibitor of histamine-2 receptors whose primary clinically important activity is inhibition of gastric secretion, suppressing both the concentration and the volume of what the stomach produces.

Omeprazole is a proton pump inhibitor. The prescription omeprazole label places it among the substituted benzimidazoles, which suppress gastric acid secretion by specific inhibition of the enzyme system at the secretory surface of the gastric parietal cell.

Who each shop label covers

Written by us

Pepcid AC is for adults and children 12 years and over, and directs that children under 12 ask a doctor. Prilosec OTC is for adults 18 years and older only.

Both are 14-day products in practice: each says to stop and ask a doctor if it is needed for more than 14 days. Only the proton pump inhibitor adds the further limit of no more than one course every four months.

Where the two labels agree completely

Written by us

Both carry the same list of reasons to see a doctor rather than keep taking the product: heartburn lasting over three months, heartburn with lightheadedness, sweating or dizziness, chest or shoulder pain with shortness of breath or pain spreading to the arms, neck or shoulders, frequent chest pain, trouble or pain swallowing, vomiting with blood, bloody or black stools, unexplained weight loss, frequent wheezing with heartburn, nausea or vomiting.

The Pepcid AC label adds one instruction the other does not carry in the same form: do not use with other acid reducers.

Common questions

Written by us

Which one works faster?: Neither label states an onset time in minutes, so this page cannot give one. What the labels do differ on is what they allow: Pepcid AC may be taken 15 to 60 minutes before food expected to cause heartburn, while Prilosec OTC states that it is not intended for immediate relief and may take 1 to 4 days for full effect.
Can they be taken together?: The Pepcid AC label says not to use it with other acid reducers. Anyone whose heartburn is not controlled by one product is directed by both labels to a doctor.
Is famotidine the same as ranitidine?: They belong to the same class of histamine-2 receptor antagonists, but they are different molecules with different labels, and this page is built only from the documents it links. Ranitidine products were withdrawn from the US market and are not covered here.

Sources

Every fact above comes from one of these documents. The date is the effective date of the label version this page was built from.

FDA prescribing information for Pepcid AC
Kenvue Brands LLC. Label version 20, effective 6 February 2026.
Full label on DailyMed Approval record NDA020325
FDA prescribing information for Prilosec OTC
The Procter & Gamble Manufacturing Company. Label version 17, effective 1 October 2025.
Full label on DailyMed Approval record NDA021229

Other comparisons in this category

Page last updated: 11 August 2026

Compiled by the HealthyStudy editorial team from FDA source documents. No medical reviewer is credited on this page, because none reviewed it.