How Long Does Zantac (Ranitidine) Take To Work?

Zantac begins to work quickly but it may take longer for certain conditions, like GERD.


I started to take Zantac a few days ago. I am not feeling any relief. I was told I have GERD. How long does it usually take to start working?

Asked by dana On Dec 01, 2018

Answered by
Medical Content Reviewed By PharmacistAnswers Staff

On Dec 01, 2018


Zantac (ranitidine) will begin to work and provide symptom relief 30 to 60 minutes after taking a dose by mouth.

However, if you are taking Zantac for conditions other than heartburn or indigestion (e.g. treatment of ulcers or GERD), studies suggest that it can take a few days to a few weeks of treatment before symptoms begin to improve as it generally takes long-term acid suppression for these conditions to heal and resolve.

So in your situation, as you are treating GERD, it isn't uncommon to feel as though it isn't working after only a few days.

If your condition doesn't begin to improve, or symptoms are intolerable, you should speak with your doctor about possible alternative or add-on treatments for your situation. One option is to try another class of medications known as proton pump inhibitors.

While Zantac is effective for less severe GERD, studies show that proton pump inhibitors (PPIs) offer more rapid symptom relief and better healing. 

Guidelines for the Diagnosis and Treatment of Gastroesophageal Reflux Disease state the following:

"...but it is clear that while some patients may have relief of symptoms and improvement or healing of esophagitis on H2RAs [H2-receptor antagonists], PPIs eliminate symptoms and heal esophagitis more frequently and more rapidly than the other agents. Both higher doses and more frequent dosing of H2RAs appear to improve results in the treatment of reflux, but are still inferior to PPIs

There are numerous considerations for PPI therapy, so it is important to speak with your doctor regarding whether or not it is appropriate for your situation.

Section Summary

Zantac (ranitidine) works 30 to 60 minutes after dosing. Symptom relief from conditions like GERD can take longer, from a few days to a few weeks.

About Zantac (Ranitidine)

Zantac (ranitidine) is a H2-blocker. They work to decrease gastric acid secretion by antagonizing histamine at H2-receptors, which are located on parietal cells.

H2-blockers are used in the treatment of many gastric-related disorders including:

  • Ulcers
  • Helicobactor pylori eradication
  • Gastroesophageal reflux disease (GERD)
  • Pyrosis (heartburn)
  • Dyspepsia (indigestion)

How To Take Zantac

Zan can be taken with or without food. The presence of food in your stomach does not appear to affect the extent or rate of absorption of the drug.

To prevent symptoms of heartburn, it should be 30 to 60 minutes before eating food or drinking beverages that cause heartburn. It can also be taken as needed when symptoms occur.

Each dose lasts around 8 to 12 hours. It is indicated to be dosed up to twice a day but if symptoms don't resolve after 14 days, you should stop use and talk with your doctor.

Studies show that acid secretion is highest in the evening. Therefore, taking Zantac in the evening can be beneficial if you only plan on taking the medication once daily.


Zantac has few drug interactions at recommended doses as it doesn't inhibit the action of the cytochrome P-450 enzyme system.

Nevertheless, it needs to be used cautiously with other medications that require acid for absorption such as:

  • Ampicillin
  • Itraconazole
  • Ketoconazole
  • Iron salts
  • Dasatinib
  • Gefitinib
  • Cephalosporin antibiotics
  • Sulfonylureas (e.g. glipizide)
  • Vitamin B12

Zantac Side Effects

Zantac, and H2-blockers in general, are well tolerated. Adverse effects are usually infrequent, mild and transient. Some common adverse effects include:

  • Headache
  • Dry mouth
  • Nausea
  • Constipation
  • Diarrhea

Rarely, central nervous system (CNS) adverse reactions have been reported including:

  • Agitation
  • Confusion
  • Delirium
  • Hallucinations
  • Insomnia
  • Disorientation
  • Anxiety

The majority of reports of CNS effects involve elderly individuals. Those with kidney impairment may also be at increased risk. It isn't thought that one H2-blocker is more likely than another to cause those side effects.

There are rare reports of infection (e.g. pneumonia, strongyloidiasis) in those on long term acid-suppression therapy.

H2 Comparison

The H2-blockers have been shown in trials to have equivalent efficacy at approved doses in regard to inhibition of acid secretion and for the treatment of acid-related disorders. 

Therefore, selection of a H2-blockers is largely dependent on other factors, such as individual response and risk of drug interactions. For example, Tagamet (cimetidine) inhibits several cytochrome P450 isoenzymes and has a higher risk of drug interactions. Zantac is associated with fewer drug-drug interactions.

About the Pharmacist

Dr. Brian Staiger Pharm.D

Dr. Brian Staiger is a licensed pharmacist in New York State and the founder of He graduated from the University At Buffalo with a Doctor of Pharmacy degree in 2010. He has been featured in numerous publications including the Huffington Post as well as a variety of health and pharmacy-related blogs. Please feel free to reach out to him directly if you have any inquiries or want to connect! He's answered thousands of medication and pharmacy-related questions and he's ready to answer yours! Office: 716-389-3076

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