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 (such as 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 are: anticholinergics (such as belladonna alkaloids), arbutamine, certain drugs for high blood pressure (such as clonidine, guanadrel, guanethidine), thyroid medication.Taking MAO inhibitors with this medication may cause a serious (possibly fatal) drug interaction. Avoid taking MAO inhibitors (isocarboxazid, linezolid, metaxalone, methylene blue, moclobemide, phenelzine, procarbazine, rasagiline, safinamide, selegiline, tranylcypromine) during treatment with this medication. Most MAO inhibitors should also not be taken for two weeks before and after treatment with this medication. Ask your doctor when to start or stop taking this medication.Other medications can affect the removal of doxepin from your body, which may affect how doxepin works. Examples include cimetidine, St. John's Wort, terbinafine, drugs to treat irregular heart rate (such as propafenone, flecainide), antidepressants (such as SSRIs including paroxetine, fluoxetine, fluvoxamine), drugs used to treat seizures (such as phenobarbital, phenytoin), among others.Many drugs besides doxepin may affect the heart rhythm (QT prolongation), including amiodarone, dofetilide, halofantrine, pimozide, quinidine, procainamide, sotalol, macrolide antibiotics (such as erythromycin), sparfloxacin, among others. Before using doxepin, report all medications you are currently using to your doctor or pharmacist.Tell your doctor or pharmacist if you are taking other products that cause drowsiness such as opioid pain or cough relievers (such as codeine, hydrocodone), alcohol, marijuana (cannabis), drugs for sleep or anxiety (such as alprazolam, lorazepam, zolpidem), muscle relaxants (such as carisoprodol, cyclobenzaprine), or antihistamines (such as cetirizine, diphenhydramine).Check the labels on all your medicines (such as allergy or cough-and-cold products, diet aids) because they may contain ingredients that cause drowsiness or decongestants/stimulants that could increase your heart rate or blood pressure. Ask your pharmacist about using those products safely.