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.