Benadryl Drug Interactions

by on May 1, 2012

Benadryl can potentially interact with several other medications. These drugs can either enhance or reduce the pharmacologic effects of Benadryl. In case of any possible drug interactions, your healthcare provider may recommend dose adjustments. Do not change or discontinue medication without consulting your physician. It is recommended that patients inform their healthcare provider of all prescription and over-the-counter medications (including herbal products) before taking Benadryl.

Over 700 medications have a known interaction with Benadryl, of which,  over 2 dozen can lead to major drug interactions while the rest can cause moderate effects.

Significant Drug Interactions

Here are some of the drugs that can lead to significant drug interaction.

Acetylcholinesterase Inhibitor Medications: Combining Benadryl with and anticholinesterase drug may reduce the effects of both drugs. Close medical supervision is necessary and possible dose adjustments to avoid drug interactions. Discuss with your healthcare provider if you are taking these medications.

  • donepezil (Aricept)
  • galantamine (Razadyne)
  • rivastigmine (Exelon)
  • tacrine (Cognex)

Drugs with Anticholinergic Effects – Taking Benadryl together with drugs and substances that have anticholinergic effects increases your risk of experiencing side effects such as constipations; difficulty passing urine or scanty urine output; and dryness of mouth, nose and eyes. Inform your healthcare provider if you are taking any of these drugs:

  • atropine
  • belladonna (Donnatal, B&O Supprettes, Bellamine S)
  • benztropine (Cogentin)
  • clidinium (Librax)
  • clozapine (Clozaril)
  • darifenacin (Enablex)
  • dicyclomine (Bentyl)
  • glycopyrrolate (Robinul)
  • haloperidol (Haldol)
  • homatropine (Hycodan)
  • hyoscyamine (Levsin)
  • ipratropium (Atrovent)
  • oxybutynin (Ditropan, Oxytrol)
  • solifenacin (VESIcare)
  • scopolamine (Transderm Scop)
  • tiotropium (Spiriva)
  • tolterodine (Detrol)
  • pramlintide (Symlin).

Drugs that Cause Drowsiness: These medications prolong and intensify side effects such as drowsiness, dizziness and confusion caused by Benadryl. Be sure to check drug labels because they may contain substances that cause drowsiness. Inform your healthcare provider if you take:

  • Anxiety medications like benzodiazepines, including, alprazolam (Xanax), clonazepam (Klonopin), diazepam (Valium), lorazepam (Ativan)
  • Antipsychotic medications (e.g., chlorpromazine, risperidone, amitriptyline,  trazodone)
  • Anti-seizure drugs (e.g., carbamazepine)
  • Muscle relaxants
  • Narcotic pain relievers (e.g., codeine)
  • Sleep medications (e.g., zolpidem (Ambien) and others)
  • Tricyclic antidepressants (e.g., amitriptyline).

Monoamine Oxidase Inhibitors (MAOIs) – Combining MAOIs with Benadryl can enhance and prolong certain side effects, such as constipation; difficulty passing urine; drowsiness; and dryness of mouth, eyes and nose. Inform your healthcare provider if you are taking any of these drugs:

  • isocarboxazid (Marplan)
  • linezolid (Zyvox)
  • methylene blue
  • moclobemide (Manerix)
  • phenelzine (Nardil)
  • procarbazine (Matulane)
  • rasagiline (Azilect)
  • selegiline (Eldepryl, Emsam, Zelapar)
  • tranylcypromine (Parnate).

Other Antihistamines: Use of Benadryl together with antihistamines increases the risk of side effects. Avoid taking other antihistamines while on Benadryl treatment.

  • diphenhydramine (Benadryl) including cream, ointment, spray
  • dimenhydrinate (Dramamine).

This drug information guide does not list all drugs that can potentially interact with Benadryl. Be sure to discuss with your healthcare provider all drugs (both prescription and non-prescription drugs) that you take.