Key takeaways
- Famotidine may reduce the effectiveness of certain medications that require stomach acid for absorption, including some HIV drugs, antifungal medications, and cancer treatments.
- When combined with tizanidine or warfarin, famotidine can increase the risk of side effects such as low blood pressure, slow heart rate, excessive drowsiness, or bleeding.
- Although famotidine does not directly interact with alcohol, consuming alcohol during treatment may worsen side effects like headache and dizziness, and could increase the risk of liver damage.
Famotidine is a generic drug prescribed for conditions related to excessive stomach acid, including:
- stomach ulcers, including duodenal and gastric
- gastroesophageal reflux disease (GERD)
- erosive esophagitis (acid-related damage to the lining of the esophagus) caused by GERD
Doctors may prescribe famotidine for other indications as well.
Famotidine can interact with certain other drugs. An interaction is when one substance causes another substance to have a different effect than expected.
Famotidine comes in three forms: oral tablets, and oral liquid suspension, and a liquid solution for intravenous (IV) injection. This article focuses on potential interactions of famotidine oral tablets.
Before you start treatment with famotidine, tell your doctor and pharmacist about all prescription and over-the-counter (OTC) medications you take. By sharing this information, you may help prevent possible famotidine drug interactions.
The following table lists some of the drugs that can interact with famotidine:
| Drug class or drug name | Drug examples | Interaction result with famotidine |
| tizanidine (Zanaflex) | — | can increase the risk of side effects of tizanidine |
| warfarin (Coumadin, Jantoven) | — | can increase the effect of warfarin and raise the risk of bleeding |
| certain HIV medications | • atazanavir (Reyataz) • rilpivirine (Edurant, others) • delavirdine (Rescriptor) | can make the HIV medication less effective |
| certain antifungals | • ketoconazole (Nizoral, others) • itraconazole (Sporanox, others) | can make the antifungal less effective |
| certain cancer medications | • erlotinib (Tarceva) • nilotinib (Tasigna) • dasatinib (Sprycel) | can make the cancer drug less effective |
| certain hepatitis C medications | • ledipasvir/sofosbuvir (Harvoni) • sofosbuvir/velpatasvir (Epclusa) • sofosbuvir/velpatasvir/voxilaprevir (Vosevi) | can make the hepatitis C medication less effective |
This table does not include all possible drugs that may interact with famotidine. Here are more details about some of the drugs listed above that may interact with famotidine:
Certain HIV medications
HIV is treated with medications that lower the amount of the virus in your body.
Interaction result: Taking famotidine oral tablet with certain HIV drugs can make the HIV medication less effective.
Interaction explained: Famotidine works by reducing the amount of acid in the stomach. However, some HIV medications need a certain level of acid in the stomach to be absorbed into the body. Therefore, taking these medications together can prevent your body from absorbing the HIV drug as well as it should. This can lead to lower levels of the HIV drug in your system, which can make the HIV drug less effective.
Examples: Here are some HIV medications that may interact with famotidine:
- atazanavir (Reyataz)
- rilpivirine (Edurant, others)
- delavirdine (Rescriptor)
- fosamprenavir (Lexiva, others)
What to do: If you are taking any HIV medications, tell your doctor before you start taking famotidine. They can help determine if famotidine will interact with your HIV treatment. If so, your doctor can advise you on how to best manage the interaction. For example, some HIV drugs should not be taken with famotidine at all, while others can be taken with famotidine as long as you separate your doses.
Tizanidine (Zanaflex)
Tizanidine (Zanaflex) is used to treat muscle spasms.
Interaction result: Taking famotidine with tizanidine can increase the risk of side effects of tizanidine.
Interaction explained: Tizanidine is broken down in the body by an enzyme called CYP1A2. Famotidine may block the activity of this enzyme. Taking these medications together can slow the breakdown of tizanidine in your system, causing tizanidine to build up in your body and increasing your risk of side effects from tizanidine.
What to do: Let your doctor know if you’re taking tizanidine before you start famotidine. Doctors typically won’t prescribe tizanidine and famotidine together unless the potential benefits outweigh the risks. If you and your doctor decide that you’ll take these medications together, contact your doctor if you experience symptoms of any new or severe side effects, including low blood pressure, slow heart rate, or excessive drowsiness.
Warfarin (Coumadin)
Warfarin is a blood thinner used to prevent blood clots.
Interaction result: Taking famotidine with warfarin can increase the effect of warfarin and raise the risk of bleeding.
Interaction explained: Warfarin is partially broken down in the body by an enzyme called CYP1A2. Famotidine can block the activity of this enzyme. If these medications are taken together, warfarin may not be cleared from the body as quickly as it normally would. This can lead to higher levels of warfarin in the body, which increases its effect and the risk of bleeding.
What to do: Tell your doctor if you take warfarin before you start taking famotidine. They’ll likely monitor your INR (international normalized ratio) levels closely during treatment. Report any signs or symptoms of unusual bleeding to your doctor right away, such as nosebleeds, unexplained bruising, or bloody urine.
NOTE: For questions about a specific drug not listed or discussed above, talk with your doctor.
Famotidine does not appear to interact with alcohol. But your doctor may advise you to avoid or limit alcohol consumption during famotidine treatment.
This is because drinking alcohol while taking the drug may worsen some of famotidine’s side effects. For example, you may experience:
- nausea
- headache
- dizziness
In addition, consuming large amounts of alcohol may cause liver damage. Famotidine also may cause liver problems as a side effect. Therefore, drinking alcohol during famotidine treatment could increase risk of liver problems.
Alcohol can also worsen the condition you’re receiving famotidine to treat. For example, if you have GERD, drinking alcohol may worsen your symptoms.
Because of these factors, your doctor may advise you to avoid or limit alcohol consumption while taking famotidine. For more details, talk with your doctor.
Certain medical conditions and other factors may increase the risk of interactions with famotidine. Before you take this drug, be sure to talk with your doctor about your health history. Famotidine may not be the right treatment option if you have certain medical conditions or other factors affecting your health.
Health conditions or factors that might interact with famotidine include:
- Kidney problems: Famotidine is broken down and cleared from the body by your kidneys. If you have moderate to severe kidney problems, you may not be able to clear this drug from your body as quickly as you normally would. This can cause famotidine to build up in your body, which increases your risk of side effects. Tell your doctor if you have any kidney problems before starting famotidine. Depending on the severity of your condition, they may recommend that you take a lower dose of the drug, or they may avoid prescribing famotidine altogether.
- Older adults: Compared to younger adults, older adults (ages 65 years and older) may clear famotidine from their body more slowly. This can cause famotidine to reach higher levels in the body, which increases the risk of side effects. If you are age 65 or older, talk with your doctor about whether this drug is safe for you.
- Allergic reaction: If you’ve had an allergic reaction to famotidine or any of its ingredients, your doctor will likely not prescribe famotidine. Taking the drug could cause another allergic reaction. You can ask them about other treatments that may be better choices for you.
- Breastfeeding: It’s not known whether it’s safe to use famotidine while breastfeeding. Famotidine passes into breast milk. But it’s not known what effects famotidine may have on a child who is breastfed. If you’re breastfeeding or planning to, talk with your doctor before using famotidine.
- Pregnancy: There haven’t been enough clinical trials to determine whether famotidine is safe to use while pregnant. If you’re pregnant or planning to become pregnant, tell your doctor before starting famotidine.
Famotidine may have other interactions, such as with supplements, foods, vaccines, or even lab tests.
Supplements
It’s possible for drugs to interact with supplements such as vitamins and herbs.
Famotidine interactions with herbs
There are no specific reports of herbs interacting with famotidine. However, that doesn’t mean herbal interactions won’t occur or be recognized in the future. Because of this, it’s important to check with your doctor or pharmacist before taking any of these products during famotidine treatment.
Famotidine interactions with vitamins
There are no specific reports of vitamins interacting with famotidine. However, that doesn’t mean vitamin interactions won’t occur or be recognized in the future. Because of this, you should talk with your doctor or pharmacist before taking any vitamin product with famotidine.
Food
There are no reports of food interactions with famotidine in the drug’s prescribing information. If you’d like to learn more about eating certain foods during treatment with famotidine, talk with your doctor.
Vaccines
There aren’t any known interactions between famotidine and vaccines. Talk with your doctor or pharmacist to see whether you’re due for any vaccines.
Lab tests
Famotidine isn’t known to interact with any lab tests. If you have concerns about this medication interacting with lab tests, talk with your doctor.
FAMOTIDINE INTERACTION WITH CANNABIS OR CBDCannabis (often called marijuana) and cannabis products, such as cannabidiol (CBD), have not been specifically reported to interact with famotidine. However, as with any drug or supplement, talk with your doctor before using cannabis in combination with famotidine. The impact of cannabis may affect how well you stick to your famotidine treatment plan.
Note: Cannabis is illegal at a federal level but is legal in many states to varying degrees.
In some cases, certain factors or conditions may cause your doctor to avoid prescribing famotidine due to risk of harm.
One such famotidine contraindication is if you’ve had a previous allergic reaction to famotidine or any of its ingredients.
There are no specific reports of famotidine interacting with blood pressure medications in the drug’s prescribing information. But famotidine and some blood pressure drugs can sometimes cause nausea, dizziness, or headaches. So you may have an increased risk of these side effects if you take famotidine with certain blood pressure medications.
If you have more questions about taking famotidine with blood pressure medications, talk with your doctor.
It’s generally safe to take acetaminophen (Tylenol) with famotidine. There aren’t any reports of these medications interacting with each other in the drug’s prescribing information.
But keep in mind that both acetaminophen and famotidine can cause liver problems. This side effect isn’t likely with acetaminophen unless you take higher doses than recommended. Your risk is also increased if you consume alcohol and take these medications together.
Before taking acetaminophen or any over-the-counter medication, talk with your doctor or pharmacist. They can advise you on whether the medication is safe for you and the correct dosage to use.
You can take certain steps to help prevent interactions with famotidine. Your doctor and pharmacist are key resources, so reach out to them before starting treatment.
It’s also important to read the famotidine label and other
If famotidine doesn’t come with paperwork, you can ask your pharmacist to print a copy. If you need help reading or understanding this information, ask your doctor or pharmacist.
You can also help prevent famotidine interactions by taking it exactly as your doctor prescribes.
Famotidine is a generic medicine used to treat stomach issues like acid reflux and ulcers, but it can change how other drugs work in your body. For example, because it reduces stomach acid, it can make some medications — like those for HIV, cancer, or fungal infections — less effective since they need acid to be absorbed properly. It can also slow down how your body breaks down certain drugs, such as blood thinners or muscle relaxants, which might increase your risk of bleeding or other dangerous side effects. While there isn’t a direct interaction with alcohol, drinking while taking famotidine can make your stomach problems worse or lead to more dizziness and headaches.
Disclaimer: While Medical News Today strives for factual, comprehensive, and current drug information, this article is not a substitute for a licensed healthcare professional’s expertise. Always consult a doctor before taking or discontinuing any medication. Drug information is subject to change and may not cover all uses, directions, precautions, warnings, interactions, reactions, or adverse effects. The lack of a warning does not guarantee a drug’s safety, effectiveness, or appropriateness for all patients or specific uses. Learn more about our approach to content integrity.