Cimetidine

Headache, dizziness, drowsiness, or diarrhea may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

If your doctor has directed you to use this medication, remember that your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including: mental/mood changes (such as agitation, confusion, depression, hallucinations), trouble urinating, muscle/joint pain, breast swelling/soreness in males, decreased sexual ability (with very high doses of this medication), easy bruising/bleeding, signs of infection (such as sore throat that doesn't go away, fever, cough, trouble breathing), fast/slow/irregular heartbeat, unusual tiredness, signs of liver problems (such as nausea/vomiting that doesn't stop, stomach/abdominal pain, dark urine, yellowing eyes/skin), signs of kidney problems (such as change in the amount of urine).

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US -

Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before taking cimetidine, tell your doctor or pharmacist if you are allergic to it; or to other H2 blockers (such as famotidine, nizatidine, ranitidine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of: immune system problems, kidney problems, liver problems, certain lung diseases (chronic obstructive pulmonary disease-COPD), diabetes, other stomach problems (such as tumors).

Some symptoms may actually be signs of a more serious condition. Get medical help right away if you have: heartburn with lightheadedness/sweating/dizziness, chest/jaw/arm/shoulder pain (especially with shortness of breath, unusual sweating), unexplained weight loss.

In addition, before you self-treat with this medication, get medical help right away if you have any of these signs of a serious condition: trouble/pain swallowing food, bloody vomit, vomit that looks like coffee grounds, bloody/black stools, heartburn for over 3 months, frequent chest pain, frequent wheezing (especially with heartburn), nausea/vomiting, stomach pain.

This drug may make you dizzy or drowsy. Alcohol or marijuana (cannabis) can make you more dizzy or drowsy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages. Talk to your doctor if you are using marijuana (cannabis).

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially confusion and lung infection (pneumonia). Confusion can increase the risk of falling.

During pregnancy, cimetidine should be used only when clearly needed. Discuss the risks and benefits with your doctor.

Cimetidine passes into breast milk. Consult your doctor before breastfeeding.

See also How to Use section.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

Some products that may interact with this drug include: dofetilide, epirubicin, ticlopidine, artemether, clopidogrel, lumefantrine, metformin, moclobemide, moricizine, quinidine, silver sulfadiazine.

This medication can slow down the removal of other medications from your body, which may affect how they work. Examples of affected drugs include fezolinetant, metoprolol, tacrine, warfarin, zaleplon, calcium channel blockers (such as diltiazem), tricyclic antidepressants (such as amitriptyline), theophylline, among others.

Since cimetidine reduces the amount of acid in your stomach, it may also change the absorption of certain medications and affect how they work. Some examples of affected drugs include atazanavir, dasatinib, certain azole antifungals (such as itraconazole, ketoconazole), levoketoconazole, pazopanib, sparsentan, among others. Ask your doctor or pharmacist if any of the medications you take are affected by cimetidine and how to manage this interaction.

Cigarette smoking can affect this medication. Tell your doctor if you smoke and if you stop or start smoking while using this medication.

This medication and similar H2 blockers (such as famotidine, nizatidine, ranitidine) are available both with and without a prescription. Do not take them at the same time.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include mental/mood changes, trouble speaking, difficulty awakening.

Do not share this medication with others.

Lifestyle changes such as stress reduction programs, stopping smoking, limiting alcohol, and diet changes (such as avoiding caffeine and spicy foods) may increase the effectiveness of this medication. Talk to your doctor or pharmacist about lifestyle changes that might benefit you.

Lab and/or medical tests may be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, take it as soon as you remember. If it is near the time of the next dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.