What is Zenremac 150 mg used for? A guide on the recalled ranitidine medication

October 6, 2025 •

5 min read

The active ingredient in Zenremac 150 mg, ranitidine, was the subject of a global recall in 2020 by the FDA due to potential contamination with N-nitrosodimethylamine (NDMA), a probable human carcinogen. Before its withdrawal, Zenremac 150 mg was used to treat conditions caused by excess stomach acid, including heartburn, ulcers, and GERD.

Quick Summary

Zenremac 150 mg, a medication containing ranitidine, is no longer available due to a widespread recall over potential NDMA contamination. It was previously prescribed for acid reflux, ulcers, and GERD, but safer alternative medications are now recommended.

Key Points

Recalled due to NDMA: Zenremac 150 mg is no longer available in the US and many other countries due to a widespread recall of its active ingredient, ranitidine, over potential contamination with the probable carcinogen NDMA.
Previously treated acid-related issues: Before the recall, Zenremac 150 mg was used to treat conditions like GERD, peptic ulcers, heartburn, and Zollinger-Ellison syndrome by reducing stomach acid.
Action as an H2 blocker: The medication functioned as an H2-receptor antagonist, blocking the histamine-induced production of stomach acid.
Safe alternatives are available: Recommended alternatives include other H2 blockers (famotidine, cimetidine), stronger Proton Pump Inhibitors (PPIs like omeprazole), and fast-acting antacids.
Proper disposal is crucial: Any remaining ranitidine products should be disposed of safely according to FDA guidelines, which recommend mixing with an unappealing substance like used coffee grounds or cat litter before sealing and trashing.
Lifestyle changes are key: Effective management of acid reflux involves dietary changes, smaller meals, weight management, and avoiding eating before bedtime.

Zenremac: Clarifying the Name and the Recall

The brand name 'Zenremac' is often a common misspelling of 'Zinemac', a medication whose active ingredient was ranitidine. In April 2020, the U.S. Food and Drug Administration (FDA) requested that all manufacturers withdraw all prescription and over-the-counter (OTC) ranitidine products from the market. This was due to laboratory tests revealing that levels of N-nitrosodimethylamine (NDMA), a probable human carcinogen, could increase in ranitidine products over time and when stored at higher temperatures.

Consequently, any product containing ranitidine, including Zinemac (or Zenremac), is no longer considered safe for use and should be disposed of properly. Patients who were previously using these medications were advised to speak with a healthcare professional about alternative treatment options. The FDA confirmed that NDMA levels in some products increased to unacceptable levels, prompting the market-wide withdrawal.

Historical Uses of Zenremac (Ranitidine) 150 mg

Before its recall, Zenremac 150 mg was a widely-used medication belonging to a class of drugs known as histamine H2-receptor antagonists, or H2 blockers. Its purpose was to reduce the amount of acid produced by the stomach. It was prescribed for a variety of gastrointestinal conditions, and a lower-dose version was also available over-the-counter for occasional heartburn.

Common indications included:

Gastroesophageal Reflux Disease (GERD): A chronic condition where stomach acid flows back into the esophagus, causing heartburn, regurgitation, and potential damage to the esophageal lining.
Peptic Ulcer Disease: Used for the treatment and prevention of ulcers in the stomach and intestines.
Heartburn and Acid Indigestion: Provided relief from the burning sensation and discomfort associated with acid indigestion and sour stomach.
Erosive Esophagitis: A condition where the lining of the esophagus becomes damaged due to acid exposure.
Zollinger-Ellison Syndrome: A rare condition where the stomach produces excessive amounts of acid due to tumors.
Gastritis: Inflammation of the stomach lining.

Mechanism of Action: How Ranitidine Worked

As a histamine H2-receptor antagonist, ranitidine's mechanism was straightforward and effective. In the stomach, cells called parietal cells have histamine H2 receptors. When histamine binds to these receptors, it triggers the production of stomach acid. Ranitidine worked by competitively and reversibly blocking these H2 receptors, preventing histamine from activating them. This action effectively reduced the amount of stomach acid being produced, thereby alleviating symptoms and allowing ulcers to heal.

Why the Recall Happened: The NDMA Connection

The NDMA contamination issue first came to light when a third-party laboratory detected high levels of the impurity in ranitidine products. While initial FDA testing found acceptable levels in many samples, further investigation revealed a critical problem: NDMA levels could increase over time, especially when subjected to higher than room temperatures during shipping, storage, and handling. The FDA concluded that, given the potential for unsafe levels of NDMA to develop, it was no longer safe for the drug to remain on the market.

Ranitidine was found to have an unstable chemical structure that could degrade into NDMA. This differed from the NDMA issues seen with some angiotensin II receptor blockers (ARBs), where the contamination was traced to a specific manufacturing process. In the case of ranitidine, the instability of the molecule itself was the core issue.

Safe and Available Alternatives

Fortunately, a number of safe and effective alternatives are available to treat the conditions for which ranitidine was prescribed. These fall into a few primary categories:

Other H2 Blockers: Famotidine (Pepcid, now also used in the reformulated Zantac 360) and cimetidine (Tagamet) are H2 blockers that work similarly to ranitidine but have not been found to be contaminated with NDMA.
Proton Pump Inhibitors (PPIs): This class of medications, including omeprazole (Prilosec), lansoprazole (Prevacid), and esomeprazole (Nexium), provides stronger and longer-lasting acid reduction.
Antacids: Fast-acting antacids like Tums and Rolaids offer quick relief for mild, occasional heartburn but do not provide long-term treatment.

Comparison Table: Ranitidine (Recalled) vs. Modern Alternatives


Feature	Ranitidine (Zinemac) - Recalled	Famotidine (Pepcid, Zantac 360)	Omeprazole (Prilosec)	Antacids (e.g., Tums)
Drug Class	H2 Blocker	H2 Blocker	Proton Pump Inhibitor (PPI)	Neutralizing Agent
Mechanism	Blocks H2 receptors to decrease acid production.	Blocks H2 receptors to decrease acid production.	Blocks acid pumps to prevent acid production.	Neutralizes existing stomach acid.
Market Status	Recalled since 2020 due to NDMA.	Widely available OTC and prescription.	Widely available OTC and prescription.	Widely available OTC.
Speed of Action	Begins working within 15-30 minutes.	Offers faster relief than PPIs, typically within 15-30 minutes.	Takes 1-4 days to reach full effect.	Works almost instantly.
Duration of Effect	Up to 12 hours.	Up to 12 hours.	Up to 24 hours with once-daily dosing.	Effects are short-lived.
Best for	Was used for short-term and long-term acid control.	Short-term relief and prevention.	Long-term and persistent GERD/ulcer treatment.	Immediate, mild symptom relief.

Lifestyle Adjustments for Managing Acid Reflux

Along with medication, several lifestyle changes can effectively manage acid-related symptoms.

Dietary modifications: Avoid trigger foods such as spicy or fatty foods, citrus fruits, tomatoes, caffeine, and chocolate. Keeping a food diary can help identify personal triggers.
Smaller, more frequent meals: Eating large meals can put pressure on the stomach. Smaller, more frequent meals can help reduce the digestive load.
Avoid eating before bed: Try to avoid eating for 2-3 hours before lying down to sleep, as this helps prevent reflux.
Elevate the head of your bed: Raising the head of the bed by 6-8 inches can help prevent nighttime reflux.
Maintain a healthy weight: Excess weight, particularly around the abdomen, can increase pressure on the stomach and worsen reflux.
Quit smoking: Nicotine can weaken the lower esophageal sphincter, making reflux more likely.

Conclusion

While Zenremac 150 mg, and its active ingredient ranitidine, were once common treatments for a range of acid-related conditions, the discovery of potential NDMA contamination led to a market-wide recall in 2020. This decision was based on evidence that NDMA levels in the product could increase over time and with higher temperatures, posing a potential cancer risk. Patients are strongly advised to dispose of any remaining ranitidine products safely and consult their healthcare provider about modern, proven alternatives such as famotidine or proton pump inhibitors (PPIs). By combining appropriate medication with effective lifestyle changes, individuals can successfully manage their acid reflux and gastrointestinal health without the risks associated with ranitidine.

For proper disposal of recalled medications, visit the FDA's guidance on disposing of unused medicines.

Frequently Asked Questions

Zenremac 150 mg was recalled because its active ingredient, ranitidine, was found to potentially degrade into a cancer-causing impurity called N-nitrosodimethylamine (NDMA). The NDMA levels increased over time and with exposure to heat, posing a potential health risk.

You should stop taking the medication immediately. The FDA recommends disposing of it properly by mixing it with an undesirable substance (like cat litter or coffee grounds) in a sealed bag and putting it in the trash. Do not flush it down the toilet.

Safe and effective alternatives are available. Other H2 blockers like famotidine (Pepcid, Zantac 360) and cimetidine (Tagamet) are good options. For stronger, longer-lasting relief, Proton Pump Inhibitors (PPIs) like omeprazole (Prilosec) are recommended.

The original Zantac contained ranitidine and was recalled. The new Zantac 360 has a different active ingredient, famotidine, which has not been associated with the same NDMA contamination issues and is considered safe.

Ranitidine (now recalled) and omeprazole both reduce stomach acid but work differently. Ranitidine, an H2 blocker, provides faster, shorter relief, while omeprazole, a PPI, offers stronger, longer-lasting acid reduction, taking a few days to reach full effect.

Yes, lifestyle changes can be very effective. This includes avoiding trigger foods like spicy and fatty meals, eating smaller portions, maintaining a healthy weight, and not lying down immediately after eating.

NDMA is classified as a probable human carcinogen. While exposure may increase cancer risk over long periods, the FDA does not expect low-level, short-term exposure to cause harm. The recall was a precautionary measure to remove potential risks.